JP3671106B2 - Method for producing spherical carbon polymer, electrolyte solution used for the production, and spherical carbon polymer - Google Patents

Description

【０１０８】
ここで、ΔＨ_f ⁰(r)ＡＭ−１及びΔＨｆ°（ｒ）ＰＭ−３とは、J. J. P. Stewartによる半経験的分子起動法であるＭＮＤＯ法のパラメタリゼーションを用いる場合の反応熱の計算値である。
【０１０９】
また、クロスリンクのナンバーリングシステムは図３５に示し、これはＣ₇₀のナンバリングに準ずるものである。なお、「’」印は同じナンバリングを有する隣のＣ₇₀のものである。更に、結合長とは、前述のＭＮＤＯ／ＡＭ−１法に基づく反応熱の計算値から予測された前記クロスリンクを構成するシクロブタン環のＣ−Ｃ原子間の結合距離である。
【０１１０】
表１から、anti-syn異性体間のエネルギー差は認められない。また、Ｃ（２）−Ｃ（４）及びＣ（５）−Ｃ（６）結合間の付加反応は、Ｃ₆₀の付加反応と同程度に発熱的であり、逆にＣ（１１）−Ｃ（１２）結合間の付加反応は大きく吸熱的である。
【０１１１】
ところで、Ｃ（１）−Ｃ（２）結合は明らかに単結合であるが、この結合間の環状付加反応の反応熱はＡＭ−１及びＰＭ−３レベルでそれぞれ＋０．１９及び−１．８８kcal/molとなり、表１のＣ₁₄₀ （ｇ）とＣ₁₄₀ （ｈ）の反応熱とほぼ等しい。このことは、Ｃ（１０）−Ｃ（１１）結合間の付加反応も熱力学的に起き得ないことを示唆している。従って、Ｃ₇₀分子間の付加重合反応はＣ（２）−Ｃ（４）及びＣ（５）−Ｃ（６）結合で優先的に起き、Ｃ（９）−Ｃ（１０）結合間の重合は起きたとしてもその確率は低いものと考えられる。
【０１１２】
なお、単結合性であるＣ（１１）−Ｃ（１２）結合間の反応熱がＣ（１）−Ｃ（２）結合間の反応熱より大きく吸熱的になるのは、Ｃ₁₄₀ （ｉ）のシクロブタン構造、とりわけＣ（１１）−Ｃ（１２）結合の歪みが極めて大きいことによると考えられる。
【０１１３】
また、このような〔２＋２〕環状付加体に際してのクロスリンク結合に隣接するｓｐ² 炭素の２Ｐ^Z ローブ（電子雲）の重なりの効果を評価するために、Ｃ₇₀の２量体、Ｃ₇₀−Ｃ₆₀重合体及びＣ₇₀Ｈ₂ の生成熱の比較を行った。詳細な数値データは割愛するが、この重なりによる効果はＣ₁₄₀ （ａ）〜（ｈ）にわたってほぼ無視できると思われる。
【０１１４】
上述した計算結果は、あくまでもＭＮＤＯ近似レベルでの計算結果であるが、この結果からも、本発明によれば、Ｃ₇₀分子の環状付加重合体（図２０〜図２８）からなる球状炭素重合体が容易に生成されることが伺える。
【０１１５】
【実施例】
以下、本発明を具体的な実施例について説明するが、本発明は以下の実施例に限定されるものではない。
【０１１６】
実施例１
まず、図２に説明した装置を用いて、Ｃ₆₀分子やＣ₇₀分子を含む粗製フラーレンを作製した。
【０１１７】
直径１０ｍｍ、長さ３５ｃｍのグラファイトロッド（カーボン棒）１２を正極とし、ヘリウム雰囲気で１００Ｔｏｒｒ下、１５０アンペアの直流電流によるアーク放電を行った。
【０１１８】
原料として用いたグラファイトロッドはほとんど気化し、フラーレンを含むスス（フラーレンスーツ）が得られた後、用いた電極の極性を逆にして、本来の負極１２’上に堆積したカーボンナノチューブ等の堆積物をさらに気化させてススとした。
【０１１９】
次いで、水冷された反応室（真空容器）１０内に堆積したススを掃除機で回収し、これをトルエンで抽出して粗製フラーレンを得た。さらに、得られた粗製フラーレンをヘキサンで洗浄、乾燥後、真空昇華によって精製した。このようにして得られたフラーレンサンプルの飛行時間型質量分析（以下、ＴＯＦ−ＭＳと称することがある）の結果、主としてＣ₆₀及びＣ₇₀が、Ｃ₆₀：Ｃ₇₀＝約９：１の割合で含まれる混合物を得た。
【０１２０】
次いで、得られた粗製フラーレンをトルエン−ヘキサン混合溶媒に溶解させ、活性アルミナを充填したカラムで分離抽出を行った。用いたカラムは、長さ２００ｃｍ、直径５ｃｍである。
【０１２１】
次いで、分離されたＣ₆₀及びＣ₇₀を、それぞれヘキサンで洗浄した後、高真空中において昇華精製した。Ｃ₆₀の昇華の際の温度を５７０℃とし、Ｃ₇₀の昇華の際の温度を５８０℃とした。ＴＯＦ−ＭＳを用いて純度の確認を行った結果、両サンプルともに、Ｃ₆₀に対するＣ₇₀の存在率、或いは、Ｃ₇₀に対するＣ₆₀の存在率は、それぞれ１％以下であることが確認された。
【０１２２】
以下、このように分離したサンプルをＣ₆₀、Ｃ₇₀と呼び、粗製フラーレンを昇華しただけのサンプル（Ｃ₆₀：Ｃ₇₀＝約９：１の混合物）をフラーレン混合物と称する。
【０１２３】
次に、図１に示した装置を用いてフラーレン分子の電解重合を行った。
【０１２４】
参照電極６として銀電極、電極４及び５として白金電極を用い、また３ｇのＬｉＣｌＯ₄ を支持電解質とし、さらにトルエン：アセトニトリル＝３：１の混合溶媒５００ｍＬを使用して、５００ｍｇのＣ₆₀を溶解し、Ｃ₆₀溶解液を調製した。なお、このＣ₆₀溶解液はＣ₆₀の飽和した溶液である。
【０１２５】
まず、この溶液を用いて還元ポテンシャルを測定した結果、図７に示すような酸化還元ポテンシャルカーブを得て、第１イオン化ポテンシャル（約−０．７〜−０．６Ｖ）、第２イオン化ポテンシャル（約−１．０〜−０．９Ｖ）などのポテンシャルを決定することができた。なお、この時の掃引速度は１００ｍＶ／ｓである。
【０１２６】
また、酸化還元ポテンシャルの同じ領域での繰り返し１０サイクルの測定を行った結果を図８に示す。わずかずつではあるが、ポテンシャル曲線に変化が見られ、何らかの反応が進行していることがわかる。
【０１２７】
次に、室温（２５℃）で、第１イオン化ポテンシャルでの低電圧モードで電解を行い、白金電極（負極）上にフラーレン電解重合薄膜を形成した。電解重合を行った後、フーリエ変換赤外スペクトル（ＦＴＩＲ）及び¹³Ｃ核磁気共鳴スペクトルを測定した。ＦＴＩＲの測定結果を図９に、¹³Ｃ核磁気共鳴スペクトルの測定結果を図１１に示す。また、比較として、Ｃ₆₀蒸着膜のＦＴＩＲ測定結果を図１０に示した。
【０１２８】
図９に示したＦＴＩＲの測定結果は、図１０に示したフラーレン蒸着薄膜のＦＴＩＲ測定結果と大きく異なり、Ｃ₆₀が本来の構造では存在していないことを示した。
【０１２９】
また、¹³Ｃ核磁気共鳴スペクトルの測定に際しては、Cross-Polarizationの手法を用いることができないことから、単にマジックアングルスピニングのみを用いたマススペクトルの測定とした。但し、炭素核の磁化を磁場に対して９０度フリップさせて感度を稼いだものの、自由誘導減衰が数マイクロ秒で収束し、適切な窓関数の設定を行ってフーリエ変換した場合でも比較的ブロードな吸収となったが、図１１のスペクトル図に示すように、明らかにＣ₆₀の本来の吸収周波数１０ｋＨｚから低波数側でブロードな広がりを持つｓｐ³ 炭素に帰属される吸収線（０〜８ｋＨｚ）が明瞭に観測された。
【０１３０】
なお、この観測における急速な自由誘導減衰が生じる理由は、リチウムイオンの残存により、Ｃ₆₀ポリマー中での不対電子の存在がその大きな磁気的感受率から、炭素核の緩和、とりわけ横緩和に対して大きく影響を与えていると考えられる。
【０１３１】
また、得られた薄膜を有する白金電極を高純水中に配し、重合過程で印加したポテンシャルとは逆のポテンシャルをかけてリチウムイオンの除去を試みたが、結果をほとんど変わらなかった。従って、このような薄膜中に存在するリチウムイオン等の対イオンとＣ₆₀ポリマーとの分極構造は容易に取り除けないことが分かった。
【０１３２】
次に、窒素レーザ励起の飛行時間型質量分析計を用いてフラーレン電解重合薄膜の質量分析を行った。その結果を図１２に示す。
【０１３３】
これまでの検討から、図３に示したような重合体〔１，２−（Ｃ₆₀）₂ 〕をレーザ励起のアブレーションやイオン化等を行うことはできないことが分かっている。従って、正確に重合構造を反映した質量分析が可能かどうかは問題があるが、図１２に示すように、少なくともＣ₆₀のシーケンシャルピークが観測されているという事実から、Ｃ₆₀分子はその構造を残したまま、前述したような構造で３次元的に重合しているものと考えられる。
【０１３４】
なお、図１２においては、窒素レーザ励起の飛行時間型質量分析計を用いて質量分析をするに際し、レーザパワーを、このレーザによるＣ₆₀の重合が起きない程度まで抑えていることから、フラーレン重合体のピーク（質量数ｍ／ｚ＝１４４０付近）は極めて弱い存在率として得られている。このことは、Ｃ₆₀が電解重合膜中で本来の骨格を保存していることを示している。
【０１３５】
また、図１３に示したフラーレン蒸着薄膜のラマンシフトと図１４に示した電解重合膜のラマンシフトとを比較すると、本実施例ではフラーレンのケージ構造がＣ₆₀そのままでは存在していないことが伺える。
【０１３６】
なお、得られた薄膜のＸ線回折を測定したが、薄膜中での周期的構造の存在は確認されなかった。これは、フラーレン分子の重合体構造が得られているためであると考えられる。
【０１３７】
また、図示省略するが、得られた電解重合薄膜の透過型電子顕微鏡（ＴＥＭ）写真から、完全に鏡面化した薄膜が得られていることがわかった。なお、このように鏡面化した薄膜は、安定性に優れた薄膜であり、経時劣化が少なく、耐候性に優れた薄膜である。
【０１３８】
次に、得られた電解重合薄膜の導電性、バンドギャップの決定を行った。まず、導電性及びバンドギャップの決定に用いた手法を説明する。
【０１３９】
電解重合の際の電極上に形成されたＣ₆₀電解重合薄膜を、純水中で十分に洗浄し、真空中で十分に乾燥させた。次いで、図６に示したように電極を形成した。即ち、タングステンフィラメントによる金蒸着装置を用い、白金電極２３上に形成されたフラーレン電解重合薄膜２２上に金電極２１を形成した。
【０１４０】
このように電解重合薄膜２２をサンドイッチ状に構成したものをパラメータアナライザのチャック２４上に置き、電極基板としての白金電極２３をチャック２４に接触させた。
【０１４１】
次いで、図示省略したパラメータアナライザの端子の１つをチャック２４に直結し、パラメータアナライザの他方の端子をポジショナー探針２０に接続し、ポジショナー探針（測定チップ）２０を金電極２１に接着させた。チャック２４側を一定値（０Ｖ）とし、ポジショナー探針２０側から±５Ｖの電圧を振り、電流値の測定を行った。
【０１４２】
また、チャック２４の内側に設置されている図示省略したペリチェ素子により、−６０℃から＋１５０℃までの温度範囲で電流−電圧特性を観測し、アレニウスの式に従って電気伝導度及びバンドギャップを測定した。
【０１４３】
なお、このような測定は全てチャック２４周りを乾燥高純度窒素ガス雰囲気として行った。また、金電極２１及び白金電極２３とフラーレン電解重合薄膜２２との接合はオーム接触（オーミック）である。
【０１４４】
以下、電気的な測定データはこのような方法により決められたものである。なお、膜厚は接触型膜厚計で測定し、常磁性スピン数は電子スピン共鳴法で測定した値である。
【０１４５】
なお、本実施例では、５ｃｍ×５ｃｍの面積サイズの電解重合薄膜が得られた。また、得られた電解重合薄膜の重量は５０ｍｇであり、原料フラーレン（５００ｍｇ）から電解重合薄膜への収率は１０％程度であった。
【０１４６】
下記の値は、本実施例で得られたフラーレン電解重合薄膜の物性値である。
膜厚（接触膜厚計）：３０ｎｍ
電気伝導度 ：１．１×１０^-6Ｓ／ｃｍ
バンドギャップ ：１．９ｅＶ
常磁性スピン数 ：２．５×１０¹⁸ｓｐｉｎｓ／ｇ
【０１４７】
従って、本実施例では、電気伝導性に優れると同時に、優れた半導体的性質を有するフラーレン薄膜を得ることができた。
【０１４８】
実施例２
実施例１で得られた電解重合薄膜を純水中に設置し、電解重合の際に印加したポテンシャルとは逆のポテンシャルをかけてリチウムイオンを除くことを試みた。その後、実施例１と同様に金電極を作製し（図６）、実施例１と同様の測定を行った。この測定結果を次に示す。
膜厚（接触膜厚計）：３３ｎｍ
電気伝導度 ：１．０×１０^-6Ｓ／ｃｍ
バンドギャップ ：１．９ｅＶ
常磁性スピン数 ：１．８×１０¹⁸ｓｐｉｎｓ／ｇ
【０１４９】
従って、実施例１に比べて常磁性スピン数の減少割合が少なく、このような条件では、十分にリチウムイオンを取り除くことはできていない。
【０１５０】
実施例３
実施例１で得られた電解重合薄膜を純水中に設置し、電解重合の際に印加したポテンシャルとは逆のポテンシャルをかけ、さらにこの溶液を加熱沸騰させてリチウムイオンを除くことを試みた。その後、実施例１と同様に金電極を作製し（図６）、実施例１と同様の測定を行った。測定結果を次に示す。
膜厚（接触膜厚計）：３３ｎｍ
電気伝導度 ：０．４×１０^-6Ｓ／ｃｍ
バンドギャップ ：２．０ｅＶ
常磁性スピン数 ：０．５×１０¹⁸ｓｐｉｎｓ／ｇ
【０１５１】
従って、実施例１に比べて常磁性スピン数の減少割合が比較的大きく、電解重合の際に印加したポテンシャルとは逆のポテンシャルをかけ、さらに加熱沸騰させることによって、かなり有効にリチウムイオンを取り除くことができるものと考えられる。
【０１５２】
実施例４
実施例１における支持電解質としてのＬｉＣｌＯ₄ の代わりにtert−ブチルアンモニウムパークロレート塩を用い、この際の溶媒としてトルエンとアセトニトリルとの混合比をトルエン：アセトニトリル＝６：１とした以外は、実施例１と同様にして、酸化還元ポテンシャルの測定及びそのサイクル特性の測定、さらに、透過型電子顕微鏡による薄膜評価を行い、さらに、その物性値（膜厚、電気伝導度、バンドギャップ及び常磁性スピン数）の測定を行った。
【０１５３】
図１５は、単位秒当たり１０ｍＶの掃引速度で掃引した場合の酸化還元ポテンシャルを示し、図１６は、単位秒当たり５０ｍＶの掃引速度で掃引した場合の酸化還元ポテンシャルを示し、図１７は、単位秒当たり１００ｍＶの掃引速度で掃引した場合の酸化還元ポテンシャルを示すものである。
【０１５４】
図１５〜図１７より、掃引速度にほとんど関係なく、明瞭な還元ピークが観測された。
【０１５５】
次に、図１８に５サイクルの掃引結果を示す。なお、掃引速度は１００ｍＶ／ｓである。図１８より、わずかずつではあるが、酸化還元ポテンシャルカーブがずれていることから、明らかに何らかの反応が起きていることが示唆された。
【０１５６】
次に、図１９に、得られた電解重合薄膜の透過型電子顕微鏡（ＴＥＭ）写真を示す。すなわち、得られた電解重合薄膜は完全な鏡面状態とはなっておらず、サブミクロンサイズの粒子状の集合体が観測される。
【０１５７】
また、次に、得られた薄膜の物性値を示す。
膜厚（接触膜厚計）：２３３ｎｍ
電気伝導度 ：１．５×１０^-6Ｓ／ｃｍ
バンドギャップ ：２．０ｅＶ
常磁性スピン数 ：０．２×１０¹⁸ｓｐｉｎｓ／ｇ
【０１５８】
実施例５
支持電解質として、テトラブチルアンモニウムパークロライド、リチウムテトラフルオロボラート（ＬｉＢＦ₄ ）、リチウムヘキサフルオロホスフェート（ＬｉＰＦ₆ ）、過酸化ナトリウム（ＮａＣｌＯ₄ ）、ＬｉＣＦ₃ ＳＯ₃ 、リチウムヘキサフルオロアーセナイト（ＬｉＡｓＦ₆ ）をそれぞれ用いて、実施例１と同様の測定を行った。得られた重合体は電解重合溶液中ですべて沈殿し、白金電極状での薄膜の形成は確認されなかったが、アモルファスな重合体の形成を確認した。なお、この重合体はＬｉ塩となっていた。
【０１５９】
実施例６
実施例１と同様の系で、Ｃ₇₀の電解重合薄膜の形成を行った。
【０１６０】
白金電極上に得られた電解重合薄膜は、Ｃ₆₀のそれに比べると鏡面性はやや低いものの、良好な重合薄膜の形成が見られた。得られた薄膜の物性値は次の通りである。
膜厚（接触膜厚計）：２７ｎｍ
電気伝導度 ：１．８×１０^-6Ｓ／ｃｍ
バンドギャップ ：１．９ｅＶ
常磁性スピン数 ：２．２×１０¹⁸ｓｐｉｎｓ／ｇ
【０１６１】
実施例７
電解重合の際の温度を５０℃とした以外は、実施例１と同様にして電解重合薄膜の形成を試みた。なお、溶媒の沸点等の関係から、これ以上の温度では支持電解質は危険なことがある。
【０１６２】
薄膜の形成は短時間で進行し、沈殿物が生じると共に薄膜が得られた。この沈澱物は、アモルファスな重合体であって、Ｌｉ塩を形成していた。
【０１６３】
実施例８
電解重合の際の温度を６０℃とした以外は、実施例５と同様にして、種々の支持電解質を用いて電解重合薄膜の形成を試みた。実施例５の常温（２５℃）の場合と同様に、得られた重合体は電解重合溶液中ですべて沈殿し、白金電極状での薄膜の形成は確認されなかった。
【０１６４】
比較例１
実施例１で得られるＣ₆₀及びＣ₇₀の混合フラーレンを原料として蒸着薄膜を作製し、その物性値に関して実施例１と同様の評価を行った。以下、その測定結果を示す。
膜厚（接触膜厚計）：３３ｎｍ
電気伝導度 ：１．１×１０^-13 Ｓ／ｃｍ
バンドギャップ ：１．６ｅＶ
常磁性スピン数 ：９．６×１０¹⁶ｓｐｉｎｓ／ｇ
【０１６５】
すなわち、電気伝導度が大きくなり、常磁性スピン数が少なくなっているが、これは、リチウムイオンが存在せず、なおかつ酸素分子又は酸素原子が蒸着薄膜中に拡散、侵入したことによるものと考えられる。なお、下記比較例２及び３も同様のことが言える。
【０１６６】
比較例２
実施例１で得られるＣ₆₀を原料として蒸着薄膜を形成し、その物性値に関して実施例１と同様の評価を行った。以下、その測定結果を示す。
膜厚（接触膜厚計）：４５ｎｍ
電気伝導度 ：０．４×１０^-13 Ｓ／ｃｍ
バンドギャップ ：１．６ｅＶ
常磁性スピン数 ：８．５×１０¹⁶ｓｐｉｎｓ／ｇ
【０１６７】
比較例３
実施例１で得られるＣ₇₀を原料として蒸着薄膜を形成し、その物性値に関して実施例１と同様の評価を行った。以下、その測定結果を示す。
膜厚（接触膜厚計）：２８ｎｍ
電気伝導度 ：０．０４×１０^-13 Ｓ／ｃｍ
バンドギャップ ：１．７ｅＶ
常磁性スピン数 ：６．３×１０¹⁶ｓｐｉｎｓ／ｇ
【０１６８】
【発明の作用効果】
本発明の製造方法によれば、非水溶媒中に、Ｃ_n （但し、ｎは幾何学的に球状化合物を形成し得る整数である。）で表されるフラーレン分子を溶解し、これを電解重合して前記フラーレン分子の環状付加重合体からなる球状炭素重合体を得るので、液相での電解重合反応による環状付加重合体からなる球状炭素重合体の形成が可能であり、簡便に、かつ効率良く電気伝導性等の電子物性に優れた球状炭素重合体を形成することができる。
【０１６９】
特に、前記球状炭素重合体からなる薄膜を形成することも可能であり、この薄膜は、電気伝導性に優れ、経時劣化も少なく、耐候性にも優れた炭素薄膜となり得る。
【０１７０】
また、本発明の電解質溶液は、非水溶媒中に、Ｃ_n （但し、ｎは前記と同様である。）で表されるフラーレン分子を溶解し、これを電解重合して前記フラーレン分子の環状付加重合体からなる球状炭素重合体を得るに際して用いられ、前記フラーレン分子と、支持電解質と、前記フラーレン分子を溶解する第１溶媒と前記支持電解質を溶解する第２溶媒との混合溶媒からなる非水溶媒を主成分とする電解質溶液であるので、フラーレン分子と支持電解質との両者を溶解し、電気分解及び重合反応を可能とする電解質溶液を構成する。
【０１７１】
さらに、本発明の球状炭素重合体は、Ｃ_n （但し、ｎは前記と同様である。）で表されるフラーレン分子を電解重合して得られ、支持電解質から供された対イオンを含む環状付加重合体からなる球状炭素重合体であって、特に、電気伝導性に優れ、経時的な劣化も少なく、耐候性にも優れた炭素薄膜を形成することができる。
【図面の簡単な説明】
【図１】本発明の製造方法に使用可能な電解重合装置の一例の要部概略図である。
【図２】同、原料フラーレンの製造装置の一例の概略断面図である。
【図３】本発明の球状炭素重合体の部分構造の一例としてＣ₆₀分子の２量体構造〔１，２−（Ｃ₆₀）₂ 〕を示す図である。
【図４】同、球状炭素重合体の他の部分構造の一例としてＣ₆₀分子の３量体構造（Ｃ₁₈₀ ）を示す図である。
【図５】同、球状炭素重合体の他の部分構造の一例としてＣ₆₀分子の４量体構造（Ｃ₂₄₀ ）を示す図である。
【図６】本実施例で用いた薄膜の電子物性測定装置の概略断面図である。
【図７】実施例１で得られた酸化還元ポテンシャルカーブである。
【図８】同、酸化還元ポテンシャルのサイクル特性である。
【図９】同、電解重合薄膜の赤外スペクトル（ＦＲＩＲ）である。
【図１０】フラーレン蒸着膜の赤外スペクトル（ＦＲＩＲ）である。
【図１１】実施例１で得られた電解重合薄膜の¹³Ｃ核磁気共鳴スペクトル（¹³Ｃ−ＮＭＲ）である。
【図１２】同、電解重合薄膜の飛行時間型質量分析計（ＴＯＦ−ＭＳ）による質量分析結果である。
【図１３】フラーレン蒸着膜のラマンシフトである。
【図１４】実施例１で得られた電解重合薄膜のラマンシフトである。
【図１５】実施例４で得られた酸化還元ポテンシャル（掃引速度１０ｍＶ／ｓ）である。
【図１６】同、酸化還元ポテンシャル（掃引速度５０ｍＶ／ｓ）である。
【図１７】同、酸化還元ポテンシャル（掃引速度１００ｍＶ／ｓ）である。
【図１８】同、酸化還元ポテンシャルのサイクル特性である。
【図１９】同、電解重合薄膜の透過型電子顕微鏡写真（ＴＥＭ）である。
【図２０】本発明の球状炭素重合体の部分構造の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ａ）〕を示す図である。
【図２１】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｂ）〕を示す図である。
【図２２】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｃ）〕を示す図である。
【図２３】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｄ）〕を示す図である。
【図２４】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｅ）〕を示す図である。
【図２５】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｆ）〕を示す図である。
【図２６】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｇ）〕を示す図である。
【図２７】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｈ）〕を示す図である。
【図２８】同、球状炭素重合体の部分構造の他の一例としてＣ₇₀の２量体〔Ｃ₁₄₀ （ｉ）：Ｄ_2h対称〕を示す図である。
【図２９】Ｃ₆₀分子の分子構造を示す図である。
【図３０】Ｃ₇₀分子の分子構造を示す図である。
【図３１】 [2+2] 環状付加反応による１，２−（Ｃ₆₀）₂ の分子構造（ａ）、Ｄ_2h対称のＣ₁₁₆ の分子構造（ｂ）である。
【図３２】１，２−（Ｃ₆₀）₂ の構造緩和過程と生じると考えられるＣ₁₂₀ （ｂ）の分子構造である。
【図３３】同、構造緩和過程と生じると考えられるＣ₁₂₀ （ｃ）の分子構造である。
【図３４】同、構造緩和過程と生じると考えられるＣ₁₂₀ （ｄ）の分子構造である。
【図３５】Ｃ₇₀分子のナンバリングシステムを説明するための図である。
【符号の説明】
１…電解セル、２…溶媒、３…マグネチックスターラー、
４、５…電極、６…参照電極、７…ガス導入管、８…不活性ガス、
９…ポテンショスタット、１０…真空容器、
１２、１２’…グラファイト電極（対向電極）、１３…基板、
１４…電源、１５…ガス導入口、１６…ガス排出口、
１７、１８…ガス、２０…ポジショナー探針、２１…金電極、
２２…フラーレン電解重合薄膜、２３…電極、２４…チャック[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a spherical carbon polymer by electrolytic polymerization of fullerene molecules, an electrolyte solution used for the production, and a spherical carbon polymer.
[0002]
[Prior art]
Fullerene is C₆₀[See FIGS. 29 (A) and 29 (B)] and C₇₀[See FIGS. 30 (A) and 30 (B)] is a generic name for spherical carbon molecules, etc., and was discovered in a mass spectrometry spectrum of a cluster beam by laser ablation of carbon in 1985 (Kroto, HW; Heath, JR; O'Brien, SC; Curl, RF; Smalley, RE Nature 1985, 318, 162.).
[0003]
It was not until 1990 that the existence of fullerene, a spherical carbon compound, was clarified as the third crystalline carbon after diamond and graphite, and a macroscopic synthesis method was established (Kratschmer, W .; Fostiropoulos Huffman, DR Chem. Phys. Lett. 1990, 170, 167. and Kratschmer, W .; Lamb, LD; Fostiropoulos, K .; Huffman, DR Nature 1990, 347, 354.).
[0004]
Fullerene by carbon arc discharge method in 1990 (C₆₀Since the discovery of the production method, fullerene has attracted attention as a carbon-based semiconductor material. Since fullerene molecules can be easily vaporized under vacuum or reduced pressure, the fullerene molecules are easy to form a deposited thin film.
[0005]
Fullerene is a series of spherical carbon compounds consisting only of carbon, and C is composed of 60 carbons.₆₀And so-called Higher Fullerenes consisting of an even number of carbons, and includes 12 5-membered rings and 20 or more 6-membered rings. That is, 60, 70, 76, 78, 80, 82, 84, etc. (the number of carbon atoms is selected from a number that can form a spherical structure geometrically) is spherical. Spherical carbon C that forms a cluster (molecular assembly) by bonding to_nAnd C respectively₆₀, C₇₀, C₇₆, C₇₈, C₈₀, C₈₂, C₈₄And so on.
[0006]
For example C₆₀Has a polyhedral structure called “truncated icosahedron” in which all the vertices of the regular icosahedron are cut off to form a regular pentagon, and as shown in FIG. 29, all the 60 vertices of this polyhedron are carbon atoms This is a cluster substituted with C and has an official soccer ball type molecular structure. Similarly, C shown in FIG.₇₀And C₇₆, C₈₄Have a rugby ball type molecular structure.
[0007]
Such fullerenes have been studied for various uses, such as C₆₀Since it has been confirmed that a substance in which fullerene is doped with an alkali metal exhibits superconductivity, its application as an electronic material has been actively studied.
[0008]
However, the most obtainable C₆₀Or C₇₀In the case of fullerene molecules such as, since the dipole moment in the molecule is zero, only Van der Waals force acts on the bond between molecules, and the deposited thin film obtained by vacuum deposition or the like is fragile. In making a thin film electronic device using fullerene, such vulnerability is a problem for the stability of the device.
[0009]
In addition, fullerene thin films by vapor deposition (fullerene vapor-deposited thin film: hereinafter the same) have paramagnetic centers in the thin film due to the diffusion and entry of oxygen molecules between fullerene molecules, which is problematic in terms of stability. there were.
[0010]
As a method for coping with the weakness of such a fullerene vapor-deposited thin film, in recent years, a so-called fullerene polymer thin film (fullerene polymerized thin film) production method for polymerizing fullerene molecules has been proposed.
[0011]
First, as a method for producing a fullerene polymer such as a dimer or trimer of a fullerene molecule, a method for producing a fullerene polymer by light induction is known [(a) Rao, AM; Zhou, P .; Wang, KA; Hager, GT; Holden, JM; Wang, Y .; Lee, WT; Bi, XX; Eklund, PC; Cornett, DS; Duncan, MA; Amster, IJ Science 1993, 256, 955. (b) Cornett, DC; Amster, IJ; Duncan, MA; Rao, AM; Eklund, PCJPhys. Chem. 1993, 97, 5036. (c) Li, J .; Ozawa, M .; Kino, N .; Yoshizawa, T .; Mituki, T .; Horiuchi, H .; Tachikawa, O .; Kishino, K .; Kitazawa, K. Chem. Phys. Lett. 1994, 227, 572.].
[0012]
However, in this method, light irradiation is performed on a fullerene vapor-deposited thin film prepared in advance to polymerize fullerene molecules. When fullerene molecules are polymerized, volume shrinkage of the fullerene vapor-deposited thin film occurs. Cracks and the like occurred, and there were problems in terms of strength and surface properties. Accordingly, it has been extremely difficult to produce a thin film having a uniform surface and excellent surface properties over a large area by the method for producing a photoinduced fullerene polymer thin film.
[0013]
Furthermore, it is known that fullerene polymers can be produced by applying pressure and heat to collide with fullerene molecules. However, the production of fullerene polymers is limited, and a fullerene polymer thin film (ie fullerene polymer thin film) Is difficult to form [1. Molecular collision method (a) Yeretzian, C .; Hansen, K .; Diederich, F .; Whetten, RL Nature 1992, 359, 44. (b) Whetten, RL; Yeretzian, C. Int. J. Mod. Phys, 1992, B6, 3801 (c) Hansen, K .; Yeretzian, C .; Whetten, RL Chem. Phys. Lett. 1994, 218, 462 (d) Seifelt, G .; Schmidt, R .; Int. J. Mod. Phys 1992, B6, 384.5.2. Ion beam method (a) Seraphin, S .; Zhou, D .; Jiao, JJ Mater. Res. 1993, 8, 1995. (b) Gaber, H .; Busmann, HG; Hiss, R .; Hertel, IV; Romberg, H .; Fink, J .; Bruder, F .; Brenn, RJPhys. Chem, 1993, 97, 8244.3. Pressure Method (a) Duclos, SJ; Brister, K .; Haddon, RC; Kortan, AR; Thiel, FA Nature 1991, 351, 380. (b) Snoke, DW; Raptis, YS; Syassen, K. 1 Phys. Rev. 1992, B45, 14419. (c) Yamazaki, H .; Yoshida, M .; Kakudate, Y .; Usuda, S .; Yokoi, H .; Fujiwara, S .; Aoki, K .; Ruoff, R .; Malhotra Lorents, DJJPhys. Chem. 1993, 97, 11161. (d) Rao, CNR; Govindaraj, A .; Aiyer, HN; Seshadri, RJPhys. Chem. 1995, 99, 16814.).
[0014]
Powdered C₆₀By mixing the molecules with KCN while vibrating, C in a yield of about 18%.₆₀[2 + 2] adducts of molecules (C₁₂₀Molecule) is known (Guan-Wu Wang, Koichi Komatsu, Yasujiro Murata, Motoo Shiro, Nature, 5 June 1997, pages 583-586).
[0015]
However, this method does not provide C in the product.₁₂₀Ratio, that is, the purity is as low as about 20%, and a toxic CN compound is used as a catalyst, and it is a reaction in a solid phase (in powder form), and is a thin film composed of a fullerene cycloadduct. Formation is difficult, and the amount and area of generation are insufficient, and only dimers can be formed even if they are generated.
[0016]
[Problems to be solved by the invention]
Thus, in order to deal with fullerene polymerization methods such as vacuum deposition, photopolymerization, and molecular collision methods, or production methods of fullerene thin films, the present inventor has developed fullerene polymerization thin films by plasma polymerization using microwaves. Proposes a manufacturing method. The fullerene polymer thin film obtained by this method is a fullerene polymer thin film polymerized through the electronically excited state of fullerene molecules (Takahashi, N .; Dock, H .; Matsuzawa, N .; Ata, M .; J. Appl Phys. 1993, 74, 5790).
[0017]
The microwave-induced fullerene polymer thin film thus obtained is a thin film that has a remarkably increased strength, is dense, and is flexible as compared with a fullerene vapor-deposited thin film.
[0018]
That is, in fullerene vapor-deposited thin films, molecules such as oxygen and water diffuse and invade into the gaps between fullerene molecules, greatly affecting the electronic properties of the thin film. Since the electronic properties hardly change between the inside and the inside, it is considered that diffusion and penetration of molecules such as oxygen into the thin film is effectively suppressed by the denseness of the thin film.
[0019]
Actually, when the time-of-flight mass spectrometry by the laser ablation method of the fullerene polymer thin film obtained by such a method was performed, it was found that a fullerene multimer was formed. Moreover, it is thought that the electronic physical property of a fullerene polymerization thin film largely depends on the polymerization form. In fact, the mass spectrometric result obtained from such a thin film is₆₀Very similar to the results of mass spectrometry of molecular argon plasma polymerized thin films (Ata, M .; Takahashi, N .; Nojima, KJPhys. Chem. 1994, 98, 9960. and Ata, M .; Kurihara, K, ; See Takahashi, NJPhys. Chem. 1995, 101, 5.).
[0020]
In estimating the microstructure of the fullerene polymer thin film thus obtained, pulsed laser excitation time-of-flight mass spectrometry, so-called TOF-MS is useful.
[0021]
In general, the matrix assist method is used for non-destructive measurement of high molecular weight polymers. However, it is difficult to directly evaluate the actual molecular weight distribution of the polymer because there is no solvent for dissolving the fullerene polymer.
[0022]
In addition, mass evaluation by laser desorption ionization time-of-flight mass spectrometry (LDIOF-MS) also shows that there is no suitable solvent.₆₀It is difficult to accurately evaluate the actual mass distribution due to the fact that it cannot be performed by the matrix assist method due to the reaction between molecules and matrix molecules.
[0023]
However, with regard to the polymer structure, C₆₀Can be obtained from the peak positions of LITOF-MS multimers and dimer profiles observed by laser power ablation to the extent that no polymerization occurs. For example, C obtained with plasma power 50W₆₀According to LITOF-MS of the polymerized film, C₆₀Intermolecular polymerization showed that the process with the loss of 4 carbons was the most stochastic.
[0024]
That is, in the mass region of the dimer, C shown in FIG.₁₂₀Etc. are minor products, and the one with the highest probability is C₁₁₆It is. Semi-empirical C₁₂₀Based on the calculation of the dimer of₁₁₆Is D as shown in FIG._2hSymmetric C₁₁₆It is thought that.
[0025]
This C₁₁₆Is C₅₈Is obtained by recombination of C₆₀From high electronically excited states including the ionized state of C₂Is released by desorption of C₅₈[(A) Fieber-Erdmann, M. et al, Z. Phys. D 1993, 26, 308. (b) Petrie, S. et al, Nature 1993, 356, 426. (c) Eckhoff, WC; see Scuseria, GE, Chem. Phys. Lett. 1993, 216, 399.].
[0026]
This open shell C₅₈If two molecules are bonded before the transition to an adjacent structure of two five-membered rings, the C shown in FIG.₁₁₆Is obtained.
[0027]
However, the inventor₆₀The initial process of plasma polymerization is considered to be a [2 + 2] cycloaddition reaction by an excited triplet mechanism. Also, C generated with the highest probability₁₁₆Is C₆₀Produced by the [2 + 2] cycloaddition reaction from the electronically excited triplet state of₆₀)₂4 sps forming the cyclobutane ring of^ThreeCarbon atom desorption and two C₅₈This is thought to be due to recombination of open shell molecules.
[0028]
For example, C on an ionization target of TOF-MS (time-of-flight mass spectrometry: hereinafter the same)₆₀When the microcrystal is irradiated with a strong pulsed laser beam, polymerization through the electronically excited state of fullerene occurs as in the case of the above-described polymerization induced by microwaves.₆₀C with photopolymer peak₅₈, C₅₆Etc. are also observed. But C₅₈ ²⁺Or C₂ ⁺Since no fragment ions such as the above are observed, C as described in the above Fieber-Erdmann et al.₆₀ ³⁺Directly from C₅₈ ²⁺And C₂ ⁺Fragmentation to is not considered in this case.
[0029]
C₂F_FourC in gas plasma₆₀When the film is vaporized, the LDIOF-MS has C₆₀F or C₂F_FourOnly the adduct of Fragmet ion is observed and C₆₀No polymer is observed.
[0030]
C₆₀In LDIOF-MS where no polymer is observed, C₅₈, C₅₆Such ions are not observed. These observations are also₂Loss is C₆₀Supports what happens after going through the polymer.
[0031]
As described above, in the process of producing a fullerene polymer by the microwave-excited plasma polymerization method, C₂Unit loss is observed, but C during polymer formation₂Loss of 1,2- (C due to [2 + 2] cycloaddition reaction₆₀)₂Whether or not it occurs directly from [FIG. 31 (a)] is a problem. Where Murry et al. 1,2- (C₆₀)₂[(A) Murry, RL et al, Nature 1993, 366, 665. (b) Stout, DL et al, Chem. Phys. Lett. 1993, 214, 576. Osawa, See E.].
[0032]
That is, according to Murry et al., 1,2- (C₆₀)₂The initial process of structural relaxation of C is shown in FIG. 32 where the most strained 1,2-C—C bond in the cross-link site is cleaved.₁₂₀Through the structure of (b), the Stone-Wales transition [Stone, AJ; Wales, DJ Chem. Phys. Lett. 1986, 128, 501. (b) Saito, R. Chem. Phys. Lett. 1992, 195, 537 C with ladder-type cross links₁₂₀(C) (see FIG. 33) to C₁₂₀It is assumed that (d) is generated (see FIG. 34). 1,2- (C₆₀)₂[Fig. 31 (a)] to C₁₂₀(B) Although it becomes energetically unstable to (FIG. 32), C₁₂₀(C) (FIG. 33) to C₁₂₀(D) It stabilizes again as it changes to (FIG. 34).
[0033]
Thus, in the production process of the fullerene polymer by the microwave excitation plasma polymerization method, 1,2- (C by the [2 + 2] cycloaddition reaction shown in FIG.₆₀)₂Is shown in FIG. 31 (b) by the structure relaxation process._2hSymmetric C₁₁₆It is thought that the structure changes rapidly.
[0034]
As described above, in the process of forming a polymer thin film by a gas phase reaction of fullerene molecules, it is difficult to selectively obtain a polymer structure by a [2 + 2] cycloaddition reaction [[2 + 2] Cycloaddition]. In the solid phase reaction of fullerene molecules, it is difficult to obtain a fullerene cycloaddition polymer or a thin film made of a cycloaddition polymer with good productivity.
[0035]
The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an electricity composed of a cycloaddition polymer of fullerene molecules (particularly, a [2 + 2] cycloaddition polymer) by electrolytic polymerization in a liquid phase. An object of the present invention is to provide a method for producing a spherical carbon polymer excellent in electronic properties such as conductivity, an electrolyte solution used for carrying out the production method, and a spherical carbon polymer.
[0036]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventor can obtain a spherical carbon polymer excellent in electronic physical properties composed of a cycloaddition polymer of fullerene molecules by electrolytic polymerization in a specific solution. I found out.
[0037]
That is, the present invention relates to C in a non-aqueous solvent._n(Where n is an integer that can geometrically form a spherical compound.) A fullerene molecule represented by the following formula is dissolved, and this is electropolymerized to form a spherical addition polymer of the fullerene molecule. A method for producing a spherical carbon polymer (hereinafter referred to as the production method of the present invention) is provided.
[0038]
Further, the present invention provides an electrolyte solution used for carrying out the production method of the present invention in a non-aqueous solvent, C_n(Where n is an integer that can geometrically form a spherical compound.) A fullerene molecule represented by the following formula is dissolved, and this is electropolymerized to form a spherical addition polymer of the fullerene molecule. An electrolyte comprising, as a main component, a fullerene molecule, a supporting electrolyte, and a nonaqueous solvent composed of a mixed solvent of a first solvent that dissolves the fullerene molecule and a second solvent that dissolves the supporting electrolyte A solution (hereinafter referred to as the electrolyte solution of the present invention) is also provided.
[0039]
Furthermore, the present invention provides C_n(Where n is an integer capable of forming a spherical compound geometrically) and is obtained by electropolymerizing a fullerene molecule represented by a cyclic addition polymer containing a counter ion provided from a supporting electrolyte. A spherical carbon polymer (hereinafter referred to as the spherical carbon polymer of the present invention) is provided.
[0040]
The electrolytic polymerization referred to in the present invention means that the fullerene molecules are cyclically attached by dissolving the fullerene molecules in a non-aqueous solvent in advance and applying electric energy to the solution (that is, electrolysis or electrolysis). A spherical carbon polymer composed of a polymer is obtained.
[0041]
The cycloaddition polymer is a polymer obtained by addition polymerization of mutually different or identical fullerene molecules via, for example, a cyclobutane ring by a 1,2-cycle bond added to the cyclohexatrienyl moiety. Includes dimers or higher polymers.
[0042]
In addition, according to the production method of the present invention, fullerene electropolymerization by electrolysis in an electrolyte solution (non-aqueous solvent), in particular, by appropriately selecting the temperature during electropolymerization and further selecting the type of supporting electrolyte A thin film can be produced, and a uniform and large-area fullerene electrolytic polymerization thin film can be formed with a simple production apparatus. In addition, the fullerene electropolymerized thin film obtained can be a thin film having excellent electrical conductivity, less deterioration over time, and excellent weather resistance than the above-described fullerene vapor-deposited thin film.
[0043]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, as the cycloaddition polymer, a plurality of the fullerene molecules are polymerized with each other by 1,2-cycle bonds added to the cyclohexatrienyl moiety (C_n)_m[However, n is the same as described above, and m is an arbitrary natural number. ] Can be obtained.
[0044]
That is, for example, as shown in FIG.₆₀By a 1,2-cycle bond added to the cyclohexatrienyl site at positions 1 and 2 of₆₀A polymer ([2 + 2] cycloaddition polymer) in which the intermolecular molecules are polymerized via a cyclobutane ring composed of carbon atom 1, carbon atom 2, carbon atom 3, and carbon atom 4 is exemplified.
[0045]
Incidentally, the spherical carbon polymer shown in FIG.₆₀As shown in FIG.₆₀The trimer of C, as shown in FIG.₆₀These tetramers can also be obtained by the production method of the present invention, and further, a multimer obtained by addition polymerization of these spherical carbon polymers can be obtained planarly or sterically. Furthermore, C as shown in FIGS.₇₀It is also possible to obtain a dimer in which molecules are cycloadded or a multimer higher than that.
[0046]
In the present invention, the fullerene molecule is C.₆₀And / or C₇₀Fullerene molecules consisting of can be used.
[0047]
That is, in the present invention, as the fullerene molecule as a raw material, C shown in FIG.₆₀Numerator and C shown in FIG.₇₀Molecules and even mixtures thereof can be used. C₇₀When using molecules, C₆₀Like molecules, dimers or higher multimers can be formed, and when the mixture is used, C₆₀Molecule and C₇₀Multimers with molecules are formed.
[0048]
In general, fullerene molecules extracted from soot obtained by arc discharge of a carbon electrode with an organic solvent such as toluene, benzene, carbon disulfide are C₆₀Or C₇₀Besides, C₇₆, C₇₈, C₈₀, C₈₂, C₈₄And so-called higher-order fullerene molecules. In the present invention, C₇₆, C₇₈, C₈₀, C₈₂, C₈₄It is also possible to use higher-order fullerene molecules such as
[0049]
In the present invention, it is preferable that the nonaqueous solvent contains a supporting electrolyte.
[0050]
Examples of the supporting electrolyte include tetrabutylammonium perchlorate, lithium tetrafluoroborate (LiBF)._Four), Lithium hexafluorophosphate (LiPF)₆), Sodium peroxide (NaClO)_Four), LiCF_ThreeSO_ThreeLithium hexafluoroarsenite (LiAsF₆However, when these supporting electrolytes are used, the obtained spherical carbon polymer is often a precipitate in the electrolyte solution.
[0051]
In contrast, for example, lithium perchlorate (LiClO_Four) Or tert-butylammonium perchlorate salt, depending on the temperature during the electropolymerization reaction, a spherical carbon polymer (hereinafter sometimes referred to as an electropolymerized thin film) as a thin film on the electrode for electrolysis. You can also get
[0052]
In the present invention, a mixed solvent of a first solvent that dissolves the fullerene molecules and a second solvent that dissolves the supporting electrolyte may be used as the non-aqueous solvent (that is, the electrolyte solution of the present invention). desirable. The mixing ratio of the first solvent and the second solvent is preferably 1st solvent: 2nd solvent = 1: 10 to 10: 1 (volume ratio).
[0053]
As the first solvent, a low-polarity solvent having a π-electron system is preferably used. For example, at least one solvent selected from the group consisting of carbon disulfide, toluene, benzene, and orthodichlorobenzene, etc. Is mentioned.
[0054]
Further, as the second solvent, it is preferable to use a solvent having a high polarity and a large dielectric constant. For example, at least one solvent selected from the group consisting of acetonitrile, dimethylformamide, dimethylsulfoxide, and dimethylacetamide, etc. Is mentioned. Of these, acetonitrile is particularly preferable.
[0055]
That is, according to the present invention, using the above-described solvent and supporting electrolyte, the fullerene molecule as a raw material is dissolved in a non-aqueous solvent, and further, the supporting electrolyte for causing electrolysis to easily occur in this solvent coexists. By applying electric energy (potential), it is possible to form a cycloaddition polymer of fullerene molecules, and further an electropolymerized thin film.
[0056]
Here, in general, fullerene molecules are carbon disulfide (CS).₂), Soluble only in a low-polarity solvent having a π-electron system such as toluene, benzene, or orthodichlorobenzene, and even the solubility in an aliphatic solvent such as n-hexane is extremely low. Of course, it does not dissolve in a polar solvent, and this is the biggest problem when performing electropolymerization of fullerene molecules.
[0057]
This is because the supporting electrolyte usually used in electrolytic polymerization is soluble only in a polar solvent such as water.
[0058]
Therefore, in order to perform the electropolymerization of fullerene molecules, it is necessary to select a solvent system that dissolves both the fullerene molecules and the supporting electrolyte, but there is no single solvent that satisfies such requirements. In order to satisfy this requirement, a mixed solvent of a solvent that dissolves the fullerene molecule and a solvent that dissolves the supporting electrolyte is used. However, if only such a solvent is used, the fullerene molecule and / or the supporting electrolyte are used. Often the solubility is not sufficient.
[0059]
In general, an aqueous solvent has a large dielectric constant and is an excellent solvent for dissolving the supporting electrolyte, which is a salt, but water is a carbon disulfide, toluene, benzene, orthodioxide capable of dissolving fullerene molecules. It does not dissolve in solvents with low polarity having a π electron system such as chlorobenzene.
[0060]
Therefore, it is necessary to select an organic solvent having a high polarity and a high dielectric constant as the second solvent used when preparing the mixed solvent. Examples of the solvent satisfying such conditions include the above-mentioned solvents. The most suitable solvent is acetanilyl, and the solvent made of acetanilyl is used to remove organic radicals using a supporting electrolyte in an electrolytic vessel (electrolysis cell). It is a solvent used in the preparation.
[0061]
However, the solvent used in the present invention is not limited to a mixed solvent of acetanilyl and a low-polarity solvent having a π-electron system such as carbon disulfide, toluene, benzene, or orthodichlorobenzene.
[0062]
In the present invention, it is desirable to perform the electrolytic polymerization while introducing an inert gas into the non-aqueous solvent.
[0063]
For example, by using a mixed solvent of acetanilyl and a low-polarity solvent having a π-electron system such as carbon disulfide, toluene, benzene, and orthodichlorobenzene, a solvent that dissolves both the supporting electrolyte and the fullerene molecule is obtained. In addition, it is desirable to enclose this solvent in an electrolytic cell and sufficiently deaerate oxygen gas contained in the solvent. For example, by removing oxygen gas, oxygen atoms are prevented from being taken into the obtained spherical carbon polymer, and further, the electropolymerized thin film, and the expression of paramagnetic centers is suppressed to suppress the polymer, and further the thin film of the thin film. Stability can be improved.
[0064]
Next, an example of an electropolymerization apparatus that can be used in the present invention is shown in FIG. Of course, it is not limited to such an apparatus.
[0065]
The electrolysis cell 1 is provided with, for example, an electrode 4 as an anode and an electrode 5 as a cathode, and a reference connected to a potentiostat 9 so that the voltage value or current value between these electrodes can be constant. An electrode 6 is provided, and a predetermined electrical potential is applied between the electrode 4 and the electrode 5.
[0066]
The electrolysis cell 1 is provided with a gas introduction pipe 7 for introducing an inert gas 8 for removing oxygen gas or the like in the solvent 2. Further, a magnetic stirrer 3 is provided below the electrolysis cell 1 and is configured to operate a stirrer (not shown) disposed in the electrolysis cell 1.
[0067]
Using the electropolymerization apparatus having such a configuration, a non-aqueous solvent containing as a main component fullerene molecules as raw materials (hereinafter sometimes referred to as raw material fullerene), the supporting electrolyte, the first solvent, and the second solvent. (Ie, the electrolyte solution of the present invention) is placed in the electrolytic cell 1, the potentiostat 9 is operated, and a predetermined electric energy is applied between the electrode 4 and the electrode 5, the fullerene molecule becomes a negative radical (anion radical). And formed as a thin film and / or as a precipitate on the negative electrode. Note that the spherical carbon polymer obtained as a precipitate can be easily recovered by means of filtration, drying, etc., and the recovered spherical carbon polymer is hardened or kneaded into a resin, for example, It can be used as a thin film.
[0068]
The electrodes 4 and 5 are preferably metal electrodes, but may be formed of other conductive materials, and a conductive material such as metal is deposited on a substrate such as glass or silicon. May be used. Further, the type of the reference electrode 6 depends on the supporting electrolyte used, but is not limited to a specific metal.
[0069]
Degassing with the inert gas 8 can also be performed by bubbling helium gas, but other inert gases such as nitrogen and argon may be used instead of helium gas. In order to strictly remove oxygen gas and the like, a dehydrating agent is used in advance before electrolysis, and further vacuum deaeration is performed, and each solvent is stored in an ampoule and introduced into the electrolytic cell 1 through a vacuum line. It is also possible.
[0070]
Further, regarding the supporting electrolyte, the supporting electrolyte as described above can be used, and the type thereof is not particularly limited, but as described above, the electrolytic polymerization that can be formed on the electrode (particularly the cathode). The physical properties of the thin film may vary slightly depending on the electrolyte used.
[0071]
For example, a spherical carbon polymer obtained when a tert-butylammonium perchlorate salt is used as a supporting electrolyte and a large positive ion such as an ammonium salt provided from this salt is present as a counter ion. The positive ions and fullerene molecules form a coordination bond and form as a thin film (or precipitate) on the electrode in the form of a complex salt, which tends to be fragile mechanically. A spherical carbon polymer obtained when lithium is used and a lithium ion provided from this compound is present as a counter ion is formed, for example, as a thin film on an electrode, is mechanically strong and stable, and exhibits a mirror surface.
[0072]
In the above apparatus, the solution can be stirred using the magnetic stirrer 3 during the electropolymerization, but this stirrer may also serve as a heater to form a spherical carbon polymer. While applying the electrical potential, the temperature can be appropriately controlled.
[0073]
In the present invention, it is desirable that the temperature during the electrolytic polymerization is less than 50 ° C. When the temperature at this time is 50 ° C. or higher, the ratio of the spherical carbon polymer of the present invention obtained as a precipitate increases, and the boiling point of the solvent used may be exceeded.
[0074]
In the present invention, it is desirable to perform the electrolytic polymerization by applying a direct current, and it is desirable to apply the direct current under a constant voltage.
[0075]
That is, an electric potential (especially voltage) for electrolytic polymerization can be applied using, for example, a potentiostat, and this potential is applied by selecting either the constant current mode or the constant voltage mode. Can do. However, when the potential is applied in the constant current mode, a high-resistance thin film is formed on the electrode and the current value tends to decrease, and the voltage may become too high. In such a situation, the state of the polyanion of the fullerene molecule may become unstable, and it may be difficult to maintain a certain reaction.
[0076]
In the case where the electropolymerization is simply performed under a constant potential condition, for example, a simple DC power source combining a commercially available dry battery and a variable resistor may be used without using a potentiostat as shown in FIG. Is possible.
[0077]
Next, the structural example of the spherical carbon polymer based on this invention is demonstrated.
[0078]
The spherical carbon polymer obtained based on the present invention is a spherical carbon polymer comprising a cyclic addition polymer formed by an addition reaction between an anion radical of a fullerene molecule and an electrically neutral molecule. In the present invention, the spherical carbon polymer can be obtained as a thin film on the electrode used for the electrolytic polymerization and / or as a precipitate in the electrolytic polymerization.
[0079]
When the structure of the spherical carbon polymer is considered two-dimensionally, as described above, formation of a dimer (see FIG. 3) is considered as a partial structure.₆₀) And FIG. 5 (C₆₀It is thought that a partial structure as shown in Fig. 4) is possible, a polymer in which the partial structures are connected in a planar or three-dimensional manner, and a thin film made of this polymer. . Of course, C as a molecule₁₂₀, C₁₈₀, C₂₄₀The possibility of a thin film containing a spherical carbon polymer such as is also conceivable.
[0080]
In general, as represented by the term radical sponge, fullerene molecules easily undergo an addition reaction when a radical species is present to form a radical adduct. This is because the carbon atom in the fullerene molecule is sp²And sp^ThreeThis is due to being in an intermediate valence state. That is, sp associated with radical adduct formation between fullerene molecules^ThreeThis is because it is easy to form a valence state.
[0081]
Further, based on the present invention, as a result of attempting to form an electropolymerized thin film in the presence of various supporting electrolytes using the electropolymerization apparatus, the dissolved fullerene molecule becomes an electrically negative anion radical, Alternatively, in order to form a fullerene polymer thin film on the electrode by reacting with electrically neutral fullerene molecules, in addition to the selection of the supporting electrolyte described above, it is necessary to control the temperature or electrolytic potential very delicately. It is.
[0082]
That is, fullerene molecules that are dissolved and charged can be easily formed, but if the polymerization occurs in a solvent rather than the electrode surface, the polymer precipitates due to the low solubility of the fullerene polymer. There are many cases. When the amount of precipitate increases, the formation of a thin film on the electrode surface may decrease.
[0083]
Therefore, when it is intended to obtain a fullerene polymer, that is, a spherical carbon polymer composed of a cycloaddition polymer, as a thin film, it is desirable to carry out the electrolytic polymerization reaction under conditions such that precipitates are reduced. In particular, when the reaction is performed using lithium ions as positive ions (ie, counter ions) of the supporting electrolyte without heating for accelerating the reaction, a strong and glossy thin film can be obtained.
[0084]
In the present invention, in the electrolytic polymerization reaction based on the present invention, a counter ion (for example, lithium ion) provided from the supporting electrolyte may be contained in the cyclic addition polymer.
[0085]
In the present invention, a spherical carbon polymer composed of a cycloaddition polymer containing a counter ion as described above, or an electropolymerized thin film can be used, but the counter ion can be removed to some extent. .
[0086]
For example, the counter-ion is removed by placing the cycloaddition polymer in a solution such as an aqueous solution, heating the solution to boiling, and applying a potential opposite to the potential applied during the electropolymerization. can do.
[0087]
Next, the manufacturing method of the raw material fullerene used by this invention is demonstrated. This raw material fullerene can be produced by, for example, a production apparatus shown in FIG.
[0088]
First, a substrate 13 is arranged in a vacuum vessel 10 having a carbon arc portion composed of a pair of high-purity graphite (or carbon) counter electrodes (graphite electrodes) 12 and 12 ′, and gas (especially air) in the vessel 10. 18 is evacuated from the exhaust port 16 by a vacuum pump (not shown), and then an inert gas (for example, helium) 17 is introduced from the introduction port 15 to adjust the internal pressure of the container 10 to a substantially vacuum state.
[0089]
Next, the ends of the graphite high-purity carbon rods are made to face each other, a predetermined voltage and current are applied from the power source 14, the ends of the carbon rods 12 and 12 'are brought into an arc discharge state, and this state is maintained for a predetermined time. .
[0090]
During this time, the carbon rods 12 and 12 ′ are vaporized, and a soot-like substance containing fullerene is deposited on the substrate 13 provided on the inner wall surface of the container 10. Next, after the container 10 is cooled, the substrate 13 to which the soot-like substance is attached can be taken out, and a soot-like substance containing fullerene can be obtained. Note that the soot-like substance generated on the inner wall of the container 10 may be recovered without providing the substrate 13.
[0091]
Most of the substances obtained here adhere to the inner wall of the container (chamber) 10 as soot.₆₀Or C₇₀And so on, and is called a fullerene suit. This soot may contain about 10% or more of the fullerene molecule under appropriate conditions.
[0092]
In addition, fullerene molecules are extracted from the obtained fullerene suit with a π-electron solvent such as toluene or carbon disulfide, and the fullerene obtained at the stage of evaporation of this extract is called crude fullerene. Yes, C₆₀Or C₇₀And C₇₆, C₇₈, C₈₀, C₈₂, C₈₄High-order fullerene such as
[0093]
Further, the crude fullerene is separated from the simple C by, for example, column chromatography.₆₀Or C₇₀Separation and purification are possible.
[0094]
Next, C₆₀Whether or not the above-described electropolymerization reaction is thermodynamically possible with a model of a molecule will be described based on a semi-empirical level molecular orbital calculation. The counter ion considered here is lithium ion.
[0095]
According to the calculation result of the MNDO (semi-empirical molecular orbital method) approximation in which the parameters of the lithium atom are set, C₆₀, C₆₀-Li, C₁₂₀-Li, C₁₂₀-Li₂ In contrast, the following heat generation values are predicted. The calculation results are as follows.
C₆₀      : 864.4181 kcal / mol
C₆₀-Li: 763.001 kcal / mol
C₁₂₀-Li: 1525.716 kcal / mol
C₁₂₀-Li₂  : 1479.057 kcal / mol
[0096]
Where C₁₂₀Is a cyclically added C as shown in FIG.₆₀Dimer [1,2- (C₆₀)₂Although not shown, lithium ions are C₆₀Structure of polymer cross-link structure sandwiched between two fullerene molecules (C₁₂₀-Li or C₁₂₀-Li₂) Is the most stable. In addition, all the calculations of the system containing lithium in the compound were performed by the unrestricted Hartree-Fock method.
[0097]
From the calculation results, the following results (1) to (3) are derived.
[0098]
(1) C₆₀Is greatly stabilized by coordination of lithium. This is C₆₀This is due to the fact that the lowest empty orbit of lies at a position significantly lower than the free electrons.
(2) (C₆₀) + (C₆₀-Li) = (C₁₂₀-Li) + Q
The reaction heat Q is estimated to be −106.3 kcal / mol, which is an exothermic reaction, and the obtained C₁₂₀-Li is greatly stabilized.
(3) 2 (C₆₀-Li) = (C₁₂₀-Li₂+ Q
The reaction heat is predicted to be −46.945 kcal / mol, which is also an exothermic reaction.
[0099]
These calculation results are merely energy differences between the initial state and the final state in vacuum, and do not determine the potential barrier of the reaction. However, this calculation result supports that the above reaction easily occurs because the entropy such as steric hindrance contributes to the free energy of the system when the contribution is small.
[0100]
C₆₀A model calculation was performed on the heat of formation of the molecule. Next, with reference to FIGS.₇₀Consider the case of molecules.
[0101]
C₇₀Understanding intermolecular polymerization is C₆₀More complex than molecules. C used here for convenience₇₀The numbering of carbon atoms in the molecule is shown in FIG.
[0102]
C₇₀The 105 C—C bonds of C (1) -C (2), C (2) -C (4), C (4) -C (5), C using the numbering system shown in FIG. (5) -C (6), C (5) -C (10), C (9) -C (10), C (10) -C (11), represented by C (11) -C (12) Are classified into eight types of C—C bonds, among which C (2) -C (4) and C (5) -C (6) are C₆₀Have the same double bond property as C = C bond.
[0103]
Further, the 6-membered ring π electrons including C (9), C (10), C (14), and C (15) of this molecule are nonpolarized to form a 5-membered ring C (9) -C (10) The bond is double-bonded, and at the same time, the C (11) -C (12) bond is single-bonded.
[0104]
Next, C₇₀For the double bond C (2) -C (4), C (5) -C (6), C (9) -C (10), C (10) -C (11) Think. The C (11) -C (12) bond is almost a single bond, but since it is a bond across two 6-membered rings (6,6-ring fusion), the addition reactivity of this bond will also be examined.
[0105]
First, C₇₀Consider the [2 + 2] cycloaddition reaction. These five types of C—C bonds [C (2) -C (4), C (5) -C (6), C (9) -C (10), C (10) -C (11) and C From the [2 + 2] cycloaddition reaction of (11) -C (12)], 25 types of C₇₀However, for convenience of calculation, only nine addition reactions between the same C—C bonds are considered.
[0106]
Table 1 below shows two molecules of C at the MNDO / AM-1 and PM-3 levels.₇₀To C₁₄₀Heat of reaction in the production process (ΔH_f ^O(r)). In the table, C₁₄₀(A) (FIG. 20) and (b) (FIG. 21), C₁₄₀(C) (FIG. 22) and (d) (FIG. 23), C₁₄₀(E) (Fig. 24) and C₁₄₀(F) (FIG. 25) and C₁₄₀(G) (FIG. 26) and C₁₄₀(H) (FIG. 27) shows C (2) -C (4), C (5) -C (6), C (9) -C (10), and C (10) -C (11) bonds, respectively. A pair of anti-syn isomers. In addition reaction between C (11) -C (12) bonds, D_2hSymmetrical C₁₄₀(I) Only (FIG. 28) is obtained. In each figure, the upper figure is C.₁₄₀It is a model figure seen from the upper surface side of a molecule, and the lower figure is a model figure seen from the side.
[0107]

[0108]
Where ΔH_f ⁰(r) AM-1 and ΔHf ° (r) PM-3 are calculated values of the heat of reaction when using the parameterization of the MNDO method, which is a semi-empirical molecular start-up method by J. J. P. Stewart.
[0109]
The cross-link numbering system is shown in FIG.₇₀This is equivalent to the numbering. Note that the “’ ”mark indicates the adjacent C having the same numbering.₇₀belongs to. Further, the bond length is a bond distance between C-C atoms of the cyclobutane ring constituting the cross-link predicted from the calculated value of heat of reaction based on the above-mentioned MNDO / AM-1 method.
[0110]
From Table 1, no energy difference between anti-syn isomers is observed. In addition, the addition reaction between the C (2) -C (4) and C (5) -C (6) bonds is represented by C₆₀The addition reaction between the C (11) -C (12) bonds is largely endothermic.
[0111]
By the way, although the C (1) -C (2) bond is clearly a single bond, the reaction heat of the cycloaddition reaction between these bonds is +0.19 and −1.88 kcal at the AM-1 and PM-3 levels, respectively. / mol, C in Table 1₁₄₀(G) and C₁₄₀It is almost equal to the heat of reaction of (h). This suggests that the addition reaction between C (10) -C (11) bonds cannot occur thermodynamically. Therefore, C₇₀The intermolecular addition polymerization reaction occurs preferentially at the C (2) -C (4) and C (5) -C (6) bonds, and the polymerization between the C (9) -C (10) bonds occurs. However, the probability is low.
[0112]
Note that the heat of reaction between C (11) -C (12) bonds, which are single bonds, is more endothermic than the heat of reaction between C (1) -C (2) bonds.₁₄₀It is considered that the distortion of the cyclobutane structure (i), particularly the C (11) -C (12) bond, is extremely large.
[0113]
Also, sp adjacent to the crosslink bond in such a [2 + 2] cycloaddition²2P of carbon^ZIn order to evaluate the effect of the lobe (electron cloud) overlap, C₇₀Dimer of C₇₀-C₆₀Polymer and C₇₀H₂Comparison of heat of formation was performed. Although detailed numerical data is omitted, the effect of this overlap is C₁₄₀It seems that it is almost negligible over (a) to (h).
[0114]
The above-described calculation result is only a calculation result at the MNDO approximation level, but from this result, according to the present invention, C₇₀It can be seen that a spherical carbon polymer composed of a molecular cycloaddition polymer (FIGS. 20 to 28) is easily formed.
[0115]
【Example】
Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.
[0116]
Example 1
First, using the apparatus described in FIG.₆₀Molecule or C₇₀Crude fullerene containing molecules was prepared.
[0117]
Using a graphite rod (carbon rod) 12 having a diameter of 10 mm and a length of 35 cm as a positive electrode, arc discharge was performed with a direct current of 150 amperes under 100 Torr in a helium atmosphere.
[0118]
The graphite rod used as a raw material is almost vaporized, soot (fullerene suit) containing fullerene is obtained, and then the polarity of the electrode used is reversed, and deposits such as carbon nanotubes deposited on the original negative electrode 12 ' Vaporized further and made soot.
[0119]
Subsequently, the soot deposited in the water-cooled reaction chamber (vacuum vessel) 10 was collected with a vacuum cleaner, and extracted with toluene to obtain a crude fullerene. Furthermore, the obtained crude fullerene was washed with hexane, dried and then purified by vacuum sublimation. As a result of time-of-flight mass spectrometry (hereinafter sometimes referred to as TOF-MS) of the fullerene sample thus obtained,₆₀And C₇₀But C₆₀: C₇₀= A mixture with a ratio of about 9: 1 was obtained.
[0120]
Subsequently, the obtained crude fullerene was dissolved in a toluene-hexane mixed solvent, and separation and extraction were performed with a column filled with activated alumina. The column used has a length of 200 cm and a diameter of 5 cm.
[0121]
Then the separated C₆₀And C₇₀Each was washed with hexane and purified by sublimation in a high vacuum. C₆₀The temperature during the sublimation of 570 ° C., C₇₀The temperature during sublimation was set to 580 ° C. As a result of confirming the purity using TOF-MS, both samples were C₆₀Against C₇₀Presence rate, or C₇₀Against C₆₀It was confirmed that the presence rate of each was 1% or less.
[0122]
Hereinafter, the sample thus separated is referred to as C.₆₀, C₇₀This is a sample (C₆₀: C₇₀= About 9: 1 mixture) is referred to as a fullerene mixture.
[0123]
Next, fullerene molecules were electropolymerized using the apparatus shown in FIG.
[0124]
A silver electrode is used as the reference electrode 6, a platinum electrode is used as the electrodes 4 and 5, and 3 g of LiClO is used._FourUsing 500 mL of a mixed solvent of toluene: acetonitrile = 3: 1, and 500 mg of C₆₀Dissolved in C₆₀A lysis solution was prepared. This C₆₀The solution is C₆₀Is a saturated solution.
[0125]
First, as a result of measuring the reduction potential using this solution, an oxidation-reduction potential curve as shown in FIG. Potentials such as about -1.0 to -0.9 V) could be determined. The sweep speed at this time is 100 mV / s.
[0126]
In addition, FIG. 8 shows the results of repeated measurements of 10 cycles in the same region of the redox potential. Although it is slight, a change is seen in the potential curve, indicating that some kind of reaction is in progress.
[0127]
Next, electrolysis was performed in a low voltage mode at the first ionization potential at room temperature (25 ° C.) to form a fullerene electropolymerized thin film on the platinum electrode (negative electrode). After performing the electropolymerization, Fourier transform infrared spectrum (FTIR) and¹³C nuclear magnetic resonance spectra were measured. The FTIR measurement results are shown in FIG.¹³The measurement result of C nuclear magnetic resonance spectrum is shown in FIG. For comparison, C₆₀The FTIR measurement result of the deposited film is shown in FIG.
[0128]
The FTIR measurement result shown in FIG. 9 is significantly different from the FTIR measurement result of the fullerene deposited thin film shown in FIG.₆₀Showed that it does not exist in its original structure.
[0129]
Also,¹³In the measurement of C nuclear magnetic resonance spectrum, since the method of cross-polarization cannot be used, the mass spectrum was simply measured using only magic angle spinning. However, although the magnetization of the carbon nuclei was flipped 90 degrees with respect to the magnetic field to increase sensitivity, the free induction decay converged in a few microseconds, and even when the Fourier transform was performed by setting an appropriate window function, it was relatively broad. As shown in the spectrum diagram of FIG.₆₀Sp with broad broadening on the low wavenumber side from the original absorption frequency of 10kHz^ThreeAbsorption lines (0 to 8 kHz) attributed to carbon were clearly observed.
[0130]
The reason why the rapid free induction decay occurs in this observation is that the remaining lithium ions cause C₆₀The presence of unpaired electrons in the polymer is considered to have a great influence on the relaxation of carbon nuclei, especially lateral relaxation, due to its large magnetic susceptibility.
[0131]
Further, the platinum electrode having the obtained thin film was placed in high-purity water, and an attempt was made to remove lithium ions by applying a potential opposite to the potential applied in the polymerization process, but the results were almost unchanged. Therefore, counter ions such as lithium ions present in such a thin film and C₆₀It was found that the polarization structure with the polymer cannot be easily removed.
[0132]
Next, the fullerene electropolymerized thin film was subjected to mass spectrometry using a nitrogen laser-excited time-of-flight mass spectrometer. The result is shown in FIG.
[0133]
From the examination so far, the polymer [1,2- (C₆₀)₂It is known that laser ablation and ionization cannot be performed. Accordingly, it is problematic whether mass spectrometry that accurately reflects the polymerized structure is possible, but as shown in FIG.₆₀From the fact that a sequential peak of₆₀It is considered that the molecules are three-dimensionally polymerized with the structure as described above while keeping the structure.
[0134]
In FIG. 12, when performing mass analysis using a nitrogen laser-excited time-of-flight mass spectrometer, the laser power is expressed as C₆₀Therefore, the peak of the fullerene polymer (mass number m / z = 1440 vicinity) is obtained as a very weak abundance. This means that C₆₀Shows that the original skeleton is preserved in the electropolymerized membrane.
[0135]
Further, comparing the Raman shift of the fullerene vapor-deposited thin film shown in FIG. 13 with the Raman shift of the electrolytic polymerized film shown in FIG.₆₀It can be said that it does not exist as it is.
[0136]
In addition, although the X-ray diffraction of the obtained thin film was measured, presence of the periodic structure in a thin film was not confirmed. This is presumably because a polymer structure of fullerene molecules has been obtained.
[0137]
Although not shown in the drawing, it was found from a transmission electron microscope (TEM) photograph of the obtained electropolymerized thin film that a completely mirror-finished thin film was obtained. Note that the mirror-finished thin film is a thin film having excellent stability, little deterioration with time, and excellent weather resistance.
[0138]
Next, the conductivity and band gap of the obtained electropolymerized thin film were determined. First, the method used for determining the conductivity and the band gap will be described.
[0139]
C formed on the electrode during electropolymerization₆₀The electropolymerized thin film was sufficiently washed in pure water and sufficiently dried in vacuum. Next, electrodes were formed as shown in FIG. That is, the gold electrode 21 was formed on the fullerene electropolymerization thin film 22 formed on the platinum electrode 23 using a gold vapor deposition apparatus using a tungsten filament.
[0140]
The electropolymerized thin film 22 thus configured in a sandwich shape was placed on a chuck 24 of a parameter analyzer, and a platinum electrode 23 as an electrode substrate was brought into contact with the chuck 24.
[0141]
Next, one terminal of the parameter analyzer (not shown) is directly connected to the chuck 24, the other terminal of the parameter analyzer is connected to the positioner probe 20, and the positioner probe (measurement chip) 20 is bonded to the gold electrode 21. . The chuck 24 side was set to a constant value (0 V), a voltage of ± 5 V was applied from the positioner probe 20 side, and the current value was measured.
[0142]
Further, current-voltage characteristics were observed in a temperature range from −60 ° C. to + 150 ° C. with a Peltier element (not shown) installed inside the chuck 24, and the electrical conductivity and band gap were measured according to the Arrhenius equation. .
[0143]
Note that all such measurements were performed in a dry high purity nitrogen gas atmosphere around the chuck 24. Further, the junction between the gold electrode 21 and the platinum electrode 23 and the fullerene electrolytic polymerization thin film 22 is ohmic contact (ohmic).
[0144]
Hereinafter, the electrical measurement data is determined by such a method. The film thickness was measured with a contact-type film thickness meter, and the paramagnetic spin number was a value measured with an electron spin resonance method.
[0145]
In this example, an electrolytic polymerization thin film having an area size of 5 cm × 5 cm was obtained. Moreover, the weight of the obtained electropolymerization thin film was 50 mg, and the yield from the raw material fullerene (500 mg) to the electropolymerization thin film was about 10%.
[0146]
The following values are physical property values of the fullerene electropolymerized thin film obtained in this example.
Film thickness (contact film thickness meter): 30 nm
Electrical conductivity: 1.1 × 10^-6S / cm
Band gap: 1.9 eV
Paramagnetic spin number: 2.5 × 10¹⁸spins / g
[0147]
Therefore, in this example, it was possible to obtain a fullerene thin film having excellent electrical conductivity and at the same time excellent semiconductor properties.
[0148]
Example 2
The electrolytic polymerization thin film obtained in Example 1 was placed in pure water, and an attempt was made to remove lithium ions by applying a potential opposite to the potential applied during the electrolytic polymerization. Thereafter, a gold electrode was produced in the same manner as in Example 1 (FIG. 6), and the same measurement as in Example 1 was performed. The measurement results are shown below.
Film thickness (contact film thickness meter): 33 nm
Electrical conductivity: 1.0 × 10^-6S / cm
Band gap: 1.9 eV
Paramagnetic spin number: 1.8 × 10¹⁸spins / g
[0149]
Therefore, the rate of decrease in the number of paramagnetic spins is smaller than in Example 1, and lithium ions cannot be sufficiently removed under such conditions.
[0150]
Example 3
The electrolytic polymerization thin film obtained in Example 1 was placed in pure water, applied with a potential opposite to the potential applied during the electrolytic polymerization, and the solution was heated to boiling to remove lithium ions. . Thereafter, a gold electrode was produced in the same manner as in Example 1 (FIG. 6), and the same measurement as in Example 1 was performed. The measurement results are shown below.
Film thickness (contact film thickness meter): 33 nm
Electrical conductivity: 0.4 × 10^-6S / cm
Band gap: 2.0 eV
Paramagnetic spin number: 0.5 × 10¹⁸spins / g
[0151]
Therefore, the reduction rate of the paramagnetic spin number is relatively large compared to Example 1, and the lithium ion is removed quite effectively by applying a potential opposite to the potential applied during the electropolymerization and further heating and boiling. Can be considered.
[0152]
Example 4
LiClO as supporting electrolyte in Example 1_FourInstead of tert-butylammonium perchlorate salt, the redox potential of the redox potential was the same as in Example 1 except that the mixing ratio of toluene and acetonitrile was 6: 1 as toluene: acetonitrile. Measurement and measurement of the cycle characteristics, thin film evaluation with a transmission electron microscope, and measurement of physical properties (film thickness, electrical conductivity, band gap and paramagnetic spin number) were performed.
[0153]
FIG. 15 shows the redox potential when swept at a sweep rate of 10 mV per unit second, FIG. 16 shows the redox potential when swept at a sweep rate of 50 mV per unit second, and FIG. It shows the redox potential when swept at a sweep rate of 100 mV per hit.
[0154]
From FIG. 15 to FIG. 17, a clear reduction peak was observed regardless of the sweep speed.
[0155]
Next, FIG. 18 shows the sweep results of 5 cycles. The sweep speed is 100 mV / s. From FIG. 18, although the oxidation-reduction potential curve is shifted little by little, it is suggested that some kind of reaction is apparently occurring.
[0156]
Next, FIG. 19 shows a transmission electron microscope (TEM) photograph of the obtained electrolytic polymerization thin film. That is, the obtained electropolymerized thin film is not in a perfect mirror state, and submicron-sized particulate aggregates are observed.
[0157]
Next, physical property values of the obtained thin film are shown.
Film thickness (contact film thickness meter): 233 nm
Electrical conductivity: 1.5 × 10^-6S / cm
Band gap: 2.0 eV
Paramagnetic spin number: 0.2 × 10¹⁸spins / g
[0158]
Example 5
As the supporting electrolyte, tetrabutylammonium perchlorate, lithium tetrafluoroborate (LiBF)_Four), Lithium hexafluorophosphate (LiPF)₆), Sodium peroxide (NaClO)_Four), LiCF_ThreeSO_ThreeLithium hexafluoroarsenite (LiAsF₆), And the same measurement as in Example 1 was performed. The obtained polymer was all precipitated in the electrolytic polymerization solution, and formation of a thin film in the form of a platinum electrode was not confirmed, but formation of an amorphous polymer was confirmed. This polymer was a Li salt.
[0159]
Example 6
In the same system as in Example 1, C₇₀The electrolytic polymerization thin film was formed.
[0160]
The electropolymerized thin film obtained on the platinum electrode is C₆₀Although the specularity was slightly lower than that of, the formation of a good polymerized thin film was observed. The physical properties of the obtained thin film are as follows.
Film thickness (contact film thickness meter): 27nm
Electrical conductivity: 1.8 × 10^-6S / cm
Band gap: 1.9 eV
Paramagnetic spin number: 2.2 × 10¹⁸spins / g
[0161]
Example 7
The formation of an electrolytic polymerization thin film was attempted in the same manner as in Example 1 except that the temperature during the electrolytic polymerization was set to 50 ° C. Note that the supporting electrolyte may be dangerous at higher temperatures due to the boiling point of the solvent and the like.
[0162]
The formation of the thin film proceeded in a short time, and a thin film was obtained while a precipitate was formed. This precipitate was an amorphous polymer and formed a Li salt.
[0163]
Example 8
An attempt was made to form an electropolymerized thin film using various supporting electrolytes in the same manner as in Example 5 except that the temperature during electropolymerization was set to 60 ° C. As in the case of normal temperature (25 ° C.) in Example 5, all of the obtained polymer was precipitated in the electrolytic polymerization solution, and formation of a thin film in the form of a platinum electrode was not confirmed.
[0164]
Comparative Example 1
C obtained in Example 1₆₀And C₇₀A vapor-deposited thin film was prepared using the mixed fullerene as a raw material, and the same evaluation as in Example 1 was performed with respect to its physical property values. The measurement results are shown below.
Film thickness (contact film thickness meter): 33 nm
Electrical conductivity: 1.1 × 10^-13S / cm
Band gap: 1.6 eV
Paramagnetic spin number: 9.6 × 10¹⁶spins / g
[0165]
That is, the electrical conductivity increases and the paramagnetic spin number decreases, but this is thought to be due to the absence of lithium ions and the diffusion and penetration of oxygen molecules or oxygen atoms into the deposited thin film. It is done. The same applies to Comparative Examples 2 and 3 below.
[0166]
Comparative Example 2
C obtained in Example 1₆₀As a raw material, a deposited thin film was formed, and the same evaluation as in Example 1 was performed with respect to the physical property values. The measurement results are shown below.
Film thickness (contact film thickness meter): 45nm
Electrical conductivity: 0.4 × 10^-13S / cm
Band gap: 1.6 eV
Paramagnetic spin number: 8.5 × 10¹⁶spins / g
[0167]
Comparative Example 3
C obtained in Example 1₇₀As a raw material, a deposited thin film was formed, and the same evaluation as in Example 1 was performed with respect to the physical property values. The measurement results are shown below.
Film thickness (contact film thickness meter): 28nm
Electrical conductivity: 0.04 × 10^-13S / cm
Band gap: 1.7 eV
Paramagnetic spin number: 6.3 × 10¹⁶spins / g
[0168]
[Effects of the invention]
According to the production method of the present invention, C is added to the non-aqueous solvent._n(Where n is an integer that can geometrically form a spherical compound.) A fullerene molecule represented by the following formula is dissolved, and this is electropolymerized to form a spherical addition polymer of the fullerene molecule. Therefore, it is possible to form a spherical carbon polymer comprising a cycloaddition polymer by an electropolymerization reaction in a liquid phase, and a spherical carbon polymer having excellent electronic properties such as electrical conductivity can be obtained easily and efficiently. Can be formed.
[0169]
In particular, it is possible to form a thin film made of the spherical carbon polymer, and this thin film can be a carbon thin film having excellent electrical conductivity, little deterioration with time, and excellent weather resistance.
[0170]
In addition, the electrolyte solution of the present invention contains C in a non-aqueous solvent._n(Wherein n is the same as described above) and is used to obtain a spherical carbon polymer comprising a cyclic addition polymer of the fullerene molecule by dissolving the fullerene molecule represented by Since the electrolyte solution is mainly composed of a nonaqueous solvent composed of a mixed solvent of a molecule, a supporting electrolyte, a first solvent that dissolves the fullerene molecule, and a second solvent that dissolves the supporting electrolyte, the fullerene molecule and the support An electrolyte solution that dissolves both the electrolyte and enables electrolysis and polymerization reaction is formed.
[0171]
Furthermore, the spherical carbon polymer of the present invention is C_n(Wherein n is the same as described above) is a spherical carbon polymer obtained by electrolytic polymerization of a fullerene molecule represented by a cyclic addition polymer containing a counter ion provided from a supporting electrolyte, In particular, it is possible to form a carbon thin film having excellent electrical conductivity, little deterioration with time, and excellent weather resistance.
[Brief description of the drawings]
FIG. 1 is a schematic view of the essential part of an example of an electropolymerization apparatus that can be used in the production method of the present invention.
FIG. 2 is a schematic cross-sectional view of an example of a raw material fullerene production apparatus.
FIG. 3 shows an example of a partial structure of the spherical carbon polymer of the present invention.₆₀Dimer structure of molecule [1,2- (C₆₀)₂FIG.
FIG. 4 shows the C as an example of another partial structure of a spherical carbon polymer.₆₀Molecular trimer structure (C₁₈₀).
FIG. 5 shows the C as an example of another partial structure of a spherical carbon polymer.₆₀Molecular tetramer structure (C₂₄₀).
FIG. 6 is a schematic cross-sectional view of a thin-film electronic property measuring apparatus used in this example.
7 is a redox potential curve obtained in Example 1. FIG.
FIG. 8 is a cycle characteristic of the oxidation-reduction potential.
FIG. 9 is an infrared spectrum (FRIR) of the electropolymerized thin film.
FIG. 10 is an infrared spectrum (FRIR) of a fullerene deposited film.
11 is a graph showing the results of electrolytic polymerization thin film obtained in Example 1. FIG.¹³C nuclear magnetic resonance spectrum (¹³C-NMR).
FIG. 12 shows the results of mass spectrometry of an electropolymerized thin film using a time-of-flight mass spectrometer (TOF-MS).
FIG. 13 is a Raman shift of a fullerene deposited film.
14 is a Raman shift of the electropolymerized thin film obtained in Example 1. FIG.
15 is a redox potential (sweep speed of 10 mV / s) obtained in Example 4. FIG.
FIG. 16 shows the oxidation-reduction potential (sweep speed 50 mV / s).
FIG. 17 shows the oxidation-reduction potential (sweep speed: 100 mV / s).
FIG. 18 shows the cycle characteristics of the oxidation-reduction potential.
FIG. 19 is a transmission electron micrograph (TEM) of the electropolymerized thin film.
FIG. 20 shows C as an example of a partial structure of the spherical carbon polymer of the present invention.₇₀Dimer [C₁₄₀It is a figure which shows (a)].
FIG. 21 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀It is a figure which shows (b)].
FIG. 22 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀(C)].
FIG. 23 shows C as another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀(D)].
FIG. 24 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀It is a figure which shows (e)].
FIG. 25 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀(F)].
FIG. 26 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀(G)].
FIG. 27 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀(H)].
FIG. 28 shows another example of a partial structure of a spherical carbon polymer.₇₀Dimer [C₁₄₀(I): D_2hFIG.
FIG. 29 C₆₀It is a figure which shows the molecular structure of a molecule | numerator.
FIG. 30C₇₀It is a figure which shows the molecular structure of a molecule | numerator.
FIG. 31: [2 + 2] 1,2- (C₆₀)₂Molecular structure (a), D_2hSymmetrical C₁₁₆Is the molecular structure (b).
FIG. 32 shows 1,2- (C₆₀)₂The structural relaxation process of C₁₂₀It is the molecular structure of (b).
FIG. 33 shows a structure relaxation process and C considered to occur.₁₂₀It is the molecular structure of (c).
FIG. 34 shows that C is considered to be caused by the structural relaxation process.₁₂₀It is the molecular structure of (d).
FIG. 35C₇₀It is a figure for demonstrating the numbering system of a molecule | numerator.
[Explanation of symbols]
1 ... electrolytic cell, 2 ... solvent, 3 ... magnetic stirrer,
4, 5 ... electrode, 6 ... reference electrode, 7 ... gas inlet tube, 8 ... inert gas,
9 ... Potentiostat, 10 ... Vacuum container,
12, 12 '... graphite electrode (counter electrode), 13 ... substrate,
14 ... Power source, 15 ... Gas inlet, 16 ... Gas outlet,
17, 18 ... gas, 20 ... positioner probe, 21 ... gold electrode,
22 ... Fullerene electropolymerized thin film, 23 ... Electrode, 24 ... Chuck

Claims (28)

In a non-aqueous solvent, a fullerene molecule represented by C _n (where n is an integer capable of geometrically forming a spherical compound) is dissolved, and this is electropolymerized to form a cyclic attachment of the fullerene molecule. A method for producing a spherical carbon polymer, wherein a spherical carbon polymer comprising a polymer is obtained. As the cycloaddition polymer, a plurality of the fullerene molecules are polymerized with each other by 1,2-cycle bonds added to the cyclohexatrienyl moiety (C _n ) _m (where n is the same as described above) , M is an arbitrary natural number. The manufacturing method of the spherical carbon polymer of Claim 1 which obtains the polymer represented by these. Examples fullerene molecule, using a fullerene molecule consisting of C ₆₀ and / or C _70, the production method of spherical carbon polymer according to claim 1. The method for producing a spherical carbon polymer according to claim 1, wherein the nonaqueous solvent contains a supporting electrolyte. The method for producing a spherical carbon polymer according to claim 4, wherein lithium perchlorate or tert-butylammonium perchlorate salt is used as the supporting electrolyte. The method for producing a spherical carbon polymer according to claim 4, wherein a mixed solvent of a first solvent that dissolves the fullerene molecule and a second solvent that dissolves the supporting electrolyte is used as the non-aqueous solvent. The method for producing a spherical carbon polymer according to claim 6, wherein a low polarity solvent having a π electron system is used as the first solvent. The method for producing a spherical carbon polymer according to claim 7, wherein at least one solvent selected from the group consisting of carbon disulfide, toluene, benzene, and orthodichlorobenzene is used as the first solvent. The method for producing a spherical carbon polymer according to claim 6, wherein a solvent having a high polarity and a large dielectric constant is used as the second solvent. The method for producing a spherical carbon polymer according to claim 9, wherein at least one solvent selected from the group consisting of acetonitrile, dimethylformamide, dimethylsulfoxide, and dimethylacetamide is used as the second solvent. The method for producing a spherical carbon polymer according to claim 1, wherein the electrolytic polymerization is performed by applying a direct current. The method for producing a spherical carbon polymer according to claim 11, wherein the direct current is applied under a constant voltage. The method for producing a spherical carbon polymer according to claim 1, wherein the temperature during the electrolytic polymerization is less than 50C. The method for producing a spherical carbon polymer according to claim 1, wherein the electrolytic polymerization is performed while introducing an inert gas into the non-aqueous solvent. The method for producing a spherical carbon polymer according to claim 1, wherein the spherical carbon polymer is obtained as a thin film on the electrode used for the electrolytic polymerization and / or as a precipitate in the electrolytic polymerization. The manufacturing method of the spherical carbon polymer of Claim 4 which removes the counter ion provided from the said supporting electrolyte from the said cycloaddition polymer. The counter-ion is removed by placing the cycloaddition polymer in a solution and heating and boiling the solution, and at the same time applying a potential opposite to the potential applied during the electropolymerization. A method for producing the spherical carbon polymer described in 1. In a non-aqueous solvent, a fullerene molecule represented by C _n (where n is an integer capable of geometrically forming a spherical compound) is dissolved, and this is electropolymerized to form a cyclic attachment of the fullerene molecule. Non-water comprising a mixed solvent of the fullerene molecule, a supporting electrolyte, a first solvent that dissolves the fullerene molecule, and a second solvent that dissolves the supporting electrolyte, which is used when obtaining a spherical carbon polymer made of a polymer. An electrolyte solution mainly composed of a solvent. The electrolyte solution according to claim 18, wherein lithium lithium perchlorate or tert-butylammonium perchlorate salt is used as the supporting electrolyte. The electrolyte solution according to claim 18, wherein a low polarity solvent having a π electron system is used as the first solvent. 21. The electrolyte solution according to claim 20, wherein at least one solvent selected from the group consisting of carbon disulfide, toluene, benzene, and orthodichlorobenzene is used as the first solvent. The electrolyte solution according to claim 18, wherein a solvent having a high polarity and a large dielectric constant is used as the second solvent. The electrolyte solution according to claim 22, wherein at least one solvent selected from the group consisting of acetonitrile, dimethylformamide, dimethyl sulfoxide, and dimethylacetamide is used as the second solvent. A cyclic addition polymer obtained by electropolymerizing a fullerene molecule represented by C _n (where n is an integer capable of geometrically forming a spherical compound) and containing a counter ion provided from a supporting electrolyte A spherical carbon polymer comprising: The cycloaddition polymer is polymerized by 1,2-cycle bonds in which a plurality of the fullerene molecules are added to the cyclohexatrienyl moiety (C _n ) _m [wherein n is as defined above. , M is an arbitrary natural number. The spherical carbon polymer according to claim 24, which is a polymer represented by the formula: The fullerene molecule is a fullerene molecule comprising a C ₆₀ and / or C _70, spherical carbon polymer according to claim 24. The spherical carbon polymer according to claim 24, wherein the supporting electrolyte is lithium perchlorate or tert-butylammonium perchlorate salt. The spherical carbon polymer according to claim 24, obtained as a thin film on the electrode used for the electrolytic polymerization and / or as a precipitate in the electrolytic polymerization.

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