5

Synthesis and Application of Rosin-Based

Surfactants

Xiaoping Rao

5.1 Introduction

Surfactants are amphipathic molecules with both hydrophilic and hydrophobic

moieties. The amphipathic structure makes them capable of reducing surface and
interfacial tension, forming microemulsion and exhibiting some superficial or
interfacial activity in solvents [1]. Since the advent of surfactants in the twentieth
century, the use of surfactants has matured and there are now thousands of different
kinds of surfactant products on the market for use in industry. The quality of our
lives is closely related to the safe use of surfactants [2]. Nowadays, surfactants play
an important role in almost every chemical industry, including detergents, emulsions,
paints, foaming agents, paper products, cosmetics, pharmaceuticals and insecticides
[3]. The worldwide production of surfactants was about 12 million tonnes in 2008
and the demand for them is expected to increase at a rate of 3% per year [4]. With
the increasing concern for the need to save energy and protect the environment,
renewable resources is a crucial area in the search for alternatives to fossil-based raw
materials. In the surfactants field, common synthetic products from petrochemicals
have often shown good functional properties, but they do not fulfill the requirements
for environmental protection and sustainable development. There are millions of
naturally occurring compounds which can be used as raw materials for the design
of surfactants. They can incorporate special structures in the final products that may
lead to surfactants with unexpected properties. The use of naturally occurring raw
materials in surfactant synthesis is expected to provide new types of surfactants with
better biodegradability. Further, in order to achieve long-term sustainable production,
it will become necessary to use renewable sources [5]. The interest in designing highly
specialised synthetic surfactants incorporating natural structural moieties has increased
remarkably during the last few years [6]. The varieties of naturally occurring structures
provide abundant selection for surfactant design. Some natural resources can provide
hydrophilic groups, and some can provide a hydrophobic moiety. Renewable sources
of hydrophilic groups include carbohydrates, proteins, amino acids and lactic acid,
and sources of the hydrophobic moiety are steroids, monoterpenes, rosin acids, fatty

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acids and long chain alkyl groups, as well as aromatic compounds [7]. Rosin acids are
a novel source of hydrophobic groups with a tricyclic hydrophenanthrene structure
that can be used for the synthesis of surfactants with natural origins.

Since the first rosin-based surfactant (rosin acid sodium salt) was reported, the
synthesis and application of rosin-based surfactants have attracted great attention
[8]. Scientists from the United States, Japan, Germany and Russia carried out much
work from the 1920s to the 1960s. After the 1970s, with the rise in labour costs for
tapping in developed countries, the amount of gum rosin reduced greatly in those
countries, they mostly focused on the application of rosin surfactants. However,
from that time on, Chinese scientists have done much work in this field. In recent
years, many new types of surfactants such as gemini and bora surfactants derived
from rosin have been synthesised and their applications investigated. Rosin is an
important natural resource, whose main components are resin acids, and they have
attracted great interest for use in surfactant synthesis and applications because of
their special chemical structures and wide range of applications. There are three
kinds of rosin: gum rosin, wood rosin and tall oil rosin. Gum rosin occupies about
60% of the industrial market, wood rosin about 5% and tall oil rosin about 35%.
The total world annual production volume of rosin has remained at 1.1-1.2 million
tons since the 1990s. The most common pine resin acids have the molecular formula
C20H30O2, [9]. Most pine resin acids belong to three basic skeletal classes: abietane,
pimarane and isopimarane, and labdane. Rosin or modified rosin are widely used as
sizes, adhesives, printing inks, emulsifiers, and these applications account for most
of the rosin used in industry. Pine resin acids have been widely investigated, but the
industrial use of them is low because of their high cost. With the development of science
and technology, pure pine resin acids and their derivatives can be easily separated
from commercial products on a large scale. For example, dehydroabietic acid (DAA)
can be isolated by crystallisation of the 2-aminoethanol salt from disproportionate
rosin, and dehydroabietylamine can be isolated by crystallisation of the acetic acid
salt from commercial disproportionate rosin amine [10]. Rosin and its derivatives are
useful building blocks for the hydrophobic moiety of surfactants since they contain
the tricyclic hydrophenanthrene structure, and hydrophilic groups can be introduced
through reactions of carboxyl groups. The hydrophenanthrene can be obtained in
enantiomerically pure form. Chiral surfactants from rosin can be used as chiral phase
transfer catalysts and chiral separation agents. Surfactants with structures similar to
derivatives of fatty acids, amines and alcohols, can be synthesised from rosin.

5.2 Synthesis of Rosin-based Surfactants

Classification of surfactants based on the charge characteristics of their polar

(hydrophilic) head groups is commonly used. Like other surfactants, rosin-based

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surfactants can be classified into four groups: cationic, anionic, zwitterionic and
nonionic. Cationic surfactants are those that have a positive charge on their polar
head group. Anionic surfactants are those that have a negative charge on their polar
head group. Zwitterionic surfactants have the potential to have both positive and
negative charges, depending on the environment in which they are placed. Nonionic
surfactants have no charge on their head group. The methods for the synthesis of
different kinds of rosin-based surfactants are summarised below.

5.2.1 Synthesis of Cationic Surfactants

The majority of rosin-based cationic surfactants are quaternary ammonium

compounds, in which the nitrogen atom carries a positive charge. The preferred soluble
anion is a halide or methyl sulfate ion and they have the structure of N+R1R2R3R4
(R1, R2, R3 and R4 are substituted groups) [11]. There are two kinds of rosin-based
cationic surfactants. One is an ester quaternary ammonium surfactant and the
other, a dehydroabietylamine-derived quaternary ammonium surfactant. There are
two methods to prepare rosin-based quaternary ammonium compounds. One is to
quaternise a tertiary amine with a halide and most rosin-based cationic surfactants
are synthesised by this method. The other is to graft rosin derivatives with active
quaternary ammonium salts.

5.2.1.1 Rosin Acid-based Ester Quaternary Ammonium Salts

Rosin is a diterpenic monoacid with a tricyclic hydrophenanthrene structure. Due

to the steric hindrance of the tricyclic hydrophenanthrene structure, the reactions on
the carboxylic acid groups occur with some difficulties. Therefore, high temperature,
catalyst and high pressure are required in some cases. However, this shortcoming
can be overcome by changing the carboxylic acid to a more active acyl chloride
intermediate. The acyl chloride reacts with N,N-dimethylethanolamine to form the
corresponding amino ester using standard reaction conditions and then rosin-based
ester quaternary ammonium compounds can be obtained after quaternisation by
halide compounds using a standard procedure.

Radbil and co-workers used DAA or a mixture of rosin acids to synthesise quaternary
ammonium compounds through chloride intermediates. Chlorides of resin acids
prepared by phosphorus trichloride were esterified with N,N-dimethanolamine. The
corresponding ester quaternary ammonium surfactants (C01-C04) were obtained
after quaternisation with halide [12]. Their synthesis route is shown in Scheme 5.1.

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Scheme 5.1 Synthesis route of ester quaternary ammonium surfactants (C01-C04)

Rosin-based surfactants can be designed through modification of the carboxylic acid

group or hydrophenanthrene group in the molecule. The tricyclic hydrophenanthrene
structure can be modified by an acrylic group through the Diels-Alder addition
reaction, which produces dicarboxylic acids of rosin. Wang and co-workers reported
that a novel bipyridine quaternary ammonium salt cationic surfactant (C05) was
prepared by acrylic-modified rosin (Scheme 5.2). The intermediate reacted with thionyl
chloride to form a chloride intermediate, after quaternisation to form rosin-based
bora type dicationic compounds [13].

Scheme 5.2 Synthesis route of bipyridine quaternary ammonium surfactant (C05)

Under classical conditions, the reactions for synthesising cationic surfactants require
a long reaction time (from 24 to 48 h) to complete the quaternisation reaction,
which results in a lower total yield of the final products and the production of more
byproducts. Microwave activation, as a nonconventional energy source, has become
a very popular and useful technology in organic chemistry [14]. Chemical reactions
brought about by microwave irradiation have gathered momentum in recent years
mainly because of their simplicity, high yield, short time span, and ecofriendly
conditions [15-16].

Gemini surfactants have attracted great interest in recent years. They are made up of
two amphiphilic moieties connected at the head group by a spacer group [17]. Gemini

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surfactants have better surface active properties such as remarkably lower critical
micelle concentration (CMC) values than corresponding conventional surfactants of
equal chain length [18]. Jia and co-workers reported that a gemini surfactant with
rosin-based hydrophenanthrene structure (C06) was synthesised by conventional
thermal conditions and microwave irradiation, respectively (Scheme 5.3). The method
of microwave irradiation greatly reduced the reaction time with better yield compared
to the conventional method [19].

Scheme 5.3 Synthesis of gemini surfactant with rosin-based hydrophenanthrene

structure (C06)

Rosin acids can react easily with the epoxy group under mild conditions. Epoxy
chloropropane is the most widely used reagent to react with rosin and its derivatives,
in order to provide a halide or epoxy intermediate to the rosin-based skeleton in an
easy way. The intermediate can react with a tertiary amine in a standard procedure
to prepare quaternary ammonium compounds. A halide intermediate can be formed
from DAA and epoxy chloropropane (Scheme 5.4), after a standard quaternisation
procedure to prepare quaternary ammonium compounds (C07) [20]. Wei and co-
workers reported bora type bis-quaternary ammonium cationic surfactants (C08-C09)
which were synthesised from acrylic-modified rosin as shown in Scheme 5.5 [21]. Chen
and co-workers reported the synthesis of a new sulfodehydroabietic acid based on a
bis-quaternary ammonium cationic surfactant (C10), which was synthesised by the
sulfonation of DAA, followed by reaction with epoxy chloropropane and triethylamine
(Scheme 5.6) [22]. Hu and co-workers reported the synthesis of a new gemini surfactant
CsH2s-α, ω-Bis (dehydroabietylhydroxypropyltetra- methylethyldiammonium) chloride
(C11) through an epoxy chloropropane intermediate (Scheme 5.7) [23].

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Scheme 5.4 Synthesis of ester quaternary ammonium surfactant (C07)

Scheme 5.5 Synthesis of bora type bis-quaternary ammonium cationic surfactants

(C08-C09)

Scheme 5.6 Synthesis of a sulfodehydroabietic acid-based surfactant (C10)

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Scheme 5.7 Synthesis of a gemini surfactant (C11) through epoxy chloropropane

Rosin acid reacted with epoxy chloropropane in alkaline conditions to form the
corresponding ester with an epoxy group, which reacted with amine to form a
tertiary amine, and then reacted with halide to form quaternary ammonium salt
cationic surfactants (C12-C13, Scheme 5.8). Rosin acid reacted with an epoxy group
quaternary ammonium salt to form cationic surfactants directly (C14) (Scheme 5.9)
[20].

Scheme 5.8 Synthesis of cationic surfactants (C12-C13) through epoxy

chloropropane

Scheme 5.9 Synthesis of a cationic surfactant (C14) directly

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5.2.1.2 Dehydroabietylamine Derived Quaternary Ammonium Salts

The most widely used starting materials for the synthesis of rosin-based quaternary
ammonium compounds are rosin amine or dehydroabietylamine [24]. Rosin amine
or dehydroabietylamine can be used as starting materials to prepare tertiary amine in
the presence of formaldehyde and formic acid, and then the rosin based quaternary
ammonium salts can be prepared in a standard procedure called quaternisation.
N,N-Dimethyldehydroabietylamine (DMDHA) is a very important intermediate for
the synthesis of rosin-based cationic surfactants. There are two methods to synthesise
DMDHA. It can be synthesised under mild conditions, in which dehydroabietylamine,
formic acid and formaldehyde solution are refluxed together at a temperature of 65 ℃
for about 5-7 h, which gives a yield of 70-80%. The other method is hydrogenation
by formaldehyde under pressure, which gives a yield of 89-94%. Ordinarily the first
method is widely used because of the mild reaction conditions [25-27].

Wang and co-workers reported a series of quaternary ammonium salts (C15-C20)

which were synthesised from dehydroabietylamine by the formic acid and
formaldehyde method (Scheme 5.10) at atmospheric pressure [28]. Pan and co-
workers reported four novel chiral quaternary ammonium salts (C21-C24) which
were synthesised from dehydroabietylamine by the method shown in Scheme 5.11
[29]. Jia and co-workers reported the rosin-based quaternary ammonium gemini
surfactants (C25-C28) which were synthesised from dehydroabietylamine by reaction
with DMDHA and α, ω- bisbromoalkanes (Scheme 5.12) [30].

Scheme 5.10 Synthesis of cationic surfactants (C15-C20)

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Scheme 5.11 Synthesis of cationic surfactants (C21-C24) through DMDHA

Scheme 5.12 Synthesis of cationic gemini surfactants (C25-C28) through DMDHA

Rosin-based cationic surfactants can also be modified by incorporating polyethylene

oxide chains. Dehydroabietylamine reacted with epoxy under pressure with a catalyst
to form a tertiary amine, then the tertiary amine was quaternised with halide to form
ethylene oxide quaternary ammonium salts (C29-C31) [31].Their synthesis route is
shown in Scheme 5.13.

Scheme 5.13 Synthesis of polyethylene oxide cationic surfactants (C29-C31)

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Quaternary ammonium salts can also be introduced into the rosin skeleton directly.
Cai and co-workers reported the direct synthesis of 3-dehydroabietylamino-2-
hydroxypropyl trimethyl ammonium chloride (C32) from dehydroabietylamine and
3-chloro-2-hydroxypropyl trimethyl ammonium chloride in the presence of an acid-
binding agent loaded on to alumina (Scheme 5.14) [32].

Scheme 5.14 Synthesis of cationic surfactant (C32) directly

5.2.2 Synthesis of Anionic Surfactants

Anionic surfactants are the most widely used class of surfactants in industry. There are
four kinds of hydrophilic groups (carboxylates, sulfates, sulfonates and phosphates)
for rosin-based anionic surfactants, with the tricyclic hydrophenanthrene structure
as the hydrophobic group. A general formula may be ascribed to rosin based
anionic surfactants: Carboxylate: RCOO-X; Sulfate: ROSO2- X; Sulfonate: RSO3- X;
Phosphate: ROPO (OH) O-X; R is the rosin-based tricyclic hydrophenanthrene group
and X is Na or K.

Carboxylates were the earliest rosin-based surfactants. They consist of rosin soaps,
e.g., sodium, potassium or calcium rosin soaps (A01) (Scheme 5.15). The rosin is
saponified by addition of a base so that it becomes soluble in water. Since the first
report of rosin soap as an anionic surfactant by Strassbury in 1919, these compounds
have been widely used as paper sizing agents and in rubber production [20]. Rosin
acids can be modified into multicarboxylic acids by the Diels-Alder addition
reaction. Wang and co-workers reported that a new type of chiral surfactant, sodium
maleopimaric acid (SMA) (A02), was synthesised from rosin and maleic anhydride
adduct compounds and then reacted with sodium hydroxide solution by the method
shown in Scheme 5.16 [33]. Compared with rosin soap, SMA has three carboxylates
in the tricyclic structure.

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Scheme 5.15 Synthesis of rosin soaps (A01)

Scheme 5.16 Synthesis of sodium maleopimaric acid (A02)

Sulfate surfactants (A03-A05) are often prepared by the esterification of hydroxyl

derivatives of rosin by sulfonate reagents. Chlorosulfonic acid was chosen as a
sulfonating reagent to react with rosin-based alcohol. After neutralisation by an
alkali or tertiary amine, rosin-based anionic surfactants were obtained (Scheme
5.17). Concentrated sulfuric acid was also chosen as a sulfonating reagent to react
with rosin-based alcohol [34].

Scheme 5.17 Synthesis of sulfate surfactants (A03-A05)

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Sulfonate surfactants contain a sulfur atom which is directly attached to the carbon
atom of the alkyl group, giving the molecule stability against hydrolysis compared
with the sulfate surfactants. There are three methods to introduce the sulfonate group
into rosin and its derivatives: the first one is to sulfonate the hydroxyl groups directly
with sulfonating agent such as concentrated sulfuric acid, the second is to add sulfate
salt to the double bonds of rosin derivatives and the third one is to react the rosin
derivative with a functional group containing a sulfonate group. DAA has an aromatic
ring, which provides another group for preparing sulfonate anionic surfactants. Chen
and co-workers reported a new unsymmetrical bora form surfactant, (disodium
sulfodehydroabietate [A06]) which was synthesised by sulfonation of dehydroabietic
acid followed by neutralisation (Scheme 5.18) [35].

Scheme 5.18 Synthesis of bora form sulfonate surfactant (A06)

The most widely studied of rosin-based anionic surfactants are sulfonate salts, which
are usually prepared by reacting rosin acid or rosin amine with alcohol. The terminal
hydroxyl group is then esterified with maleic anhydride (MA), followed by the
addition of sulfate to the double bond to form the corresponding sulfonate anionic
surfactants (Scheme 5.19). Rosin, rosin amine or dehydroabietylamine, rosin hydroxyl
ethyl amide and acrylic rosin can be ethoxylated by epoxy and the terminal hydroxyl
group can be esterified by MA, after addition of sulfate to the double bond to form
corresponding sulfonate anionic surfactants (A07-A11) [36, 37].

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Scheme 5.19 Synthesis of sulfonate anionic surfactants (A07-A11)

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The mono- or diester of MA can be obtained by controlling the ratio of polyoxyethylene

and MA during the reaction. Anionic surfactants of rosin alcohol polyoxyethylene
monoether sodium monosulfosuccinates (A12) can be synthesised by two steps of
reactions (Scheme 5.20). The influence of the degree of polymerisation of ethylene
oxide on the physical and chemical properties of the products was also studied [38].
The sodium sulfosuccinate diester of disproportionated rosin alcohol polyoxylethylene
ether (A13) can be synthesised from disproportionated rosin alcohol polyoxylethylene
ether by changing the molar ratio of the two reaction components (Scheme 5.21) [39].

Scheme 5.20 Synthesis of rosin alcohol polyoxyethylene monoether sodium

monosulfosuccinates (A12)

Scheme 5.21 Synthesis of sodium sulfosuccinate diester of disproportionated rosin

alcohol polyoxylethylene ether (A13)

Rosin acids can be changed into acid chlorides, salts and amines, which greatly improve
the reactivity. The chlorides, salts and amines can be reacted with a sulphonate-
containing alcohol (Scheme 5.22) to form sulfonate surfactants under ambient
conditions (A14-A16). Jia and co-workers reported using dehydroabietylamine, α,
ω-dibromoalkane and sodium 2-bromoethylsulfonate as raw materials (Scheme 5.23)
for synthesising new gemini anionic surfactants (N, N′-Sodium-2-diethylsulfonate-N,
N′-didehydroabietate- a ω-diamines [A17]). [40]

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Scheme 5.22 Synthesis of sulfonate surfactants (A14-A16)

Scheme 5.23 Synthesis of gemini anionic surfactant (A17)

Alkyl phosphates are made by treating the ester ethoxylates of rosin with a
phosphorylating agent, usually phosphorous pentoxide. The reaction yields a mixture
of mono- and diesters of phosphoric acid. Wang and co-workers reported (Scheme
5.24) that a phosphate anionic surfactant was synthesised by phosphorylating
polyoxyethylene abietate (A18) using phsphorus pentoxide as the phosphorylating.
Polyoxyethylene abietate was prepared from disproportionated rosin and ethylene
oxide [41].

Scheme 5.24 Synthesis of phosphate anionic surfactant (A18)

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5.2.3 Synthesis of Zwitterionic Surfactants

When a single surfactant molecule exhibits both anionic and cationic dissociations
it is called zwitterionic [42]. The main characteristic of zwitterionic surfactants is
their dependence on the pH value of the solution in which they are dissolved. In
acid solutions, the molecule acquires a positive charge and behaves like a cationic
surfactant, whereas in alkaline solutions it becomes negatively-charged and behaves
like an anionic one [43].

The majority of rosin-based zwitterionic surfactants are amino acids, including

amino carboxylic acids, amino sulfonatic acids and amino phosphonic acids.
Cui and co-workers reported three new betaine-type amphoteric surfactants,
N–(2-dehydroabietyloxy)ethyl-N,N-dimethyl carboxymethyl betaine, N–
(2–dehydroabietyloxy)ethyl-N,N-dimethyl sulfoxypropyl betaine and N–
(2-dehydroabietyloxy) ethyl-N,N-dimethyl phosphate betaine (Z01-Z03), which were
synthesised using DAA as starting material (Scheme 5.25) [44].

Scheme 5.25 Synthesis of betaine-type amphoteric surfactants (Z01-Z03)

Rosin-based amino acids are widely investigated zwitterionic surfactants. Rosin acid
and dehydroabietylamine can be used as raw materials for the synthesis (Scheme 5.26)
of this kind of surfactant (Z04-Z08). Rosin acid chloride can react with an amino
acid to form zwitterionic surfactants. This reaction can take place with different
kind of amino acids to form different kinds of zwitterionic surfactants. Liu and co-
workers reported that abietinylglycine was synthesised by the reaction of glycine
and abietic chloride in a water/acetone system and the reaction was accelerated by
a phase transfer catalyst. Benzyl trimethylammonium bromide was a good catalyst
and pyridine was a good base for the reaction [45]. Fang and co-workers reported
using disproportionated rosin and sarcosine as the main starting materials to prepare
disproportionated rosinoyl sarcosine through a chloride intermediate in the same
way [46, 47].

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Scheme 5.26 Synthesis of rosin based amino acids surfactants (Z04-Z08).

Rosin-based aminosulfonic acids are the other important zwitterionic surfactants. A

quaternary ammonium salt derived from DAA, epichlorohydrin and trimethylamine
can be reacted with concentrated sulfuric acid to form (Scheme 5.27) a zwitterionic
surfactant (Z09) [48]. Zhao and co-workers reported (Scheme 5.28) the synthesis of
3-[(3-dehydroabietamidopropyl)dimethylammonio]-1-propanesulfonate (DHAMAP)
(Z10), a new type of chiral surfactant, from DAA. The ability of this compound
to perform chiral separation of amino acids has been investigated by capillary
electrophoresis (CE) [49]. Wang and co-workers reported a new chiral derivatising

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reagent (Scheme 5.29), dehydroabietylisothiocyante (DHAIC), which can be used

for the enantiomeric separation of chiral compounds in capillary electrophoresis
(CE) (Z11) [50].

Scheme 5.27 Synthesis of a zwitterionic surfactant (Z09)

Scheme 5.28 Synthesis of DHAMAP (Z10)

Scheme 5.29 Synthesis of DHAIC (Z11)

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5.2.4 Synthesis of Nonionic Surfactants

A nonionic surfactant has no charge groups on its head. As a consequence, these

surfactants are much less sensitive to electrolytes, and can be used in high salinity
conditions or hard water [11]. The most common nonionic surfactants are those based
on ethylene oxide and are referred to as ethoxylated surfactants. Several classes can
be distinguished: rosin acid ethoxylates, rosin alcohol ethoxylates, monoalkanolamide
ethoxylates and rosin amine ethoxylates. The other kind of rosin-based nonionic
surfactant is a sugar-based surfactant; in which glucose and sucrose were introduced to
the basic skeleton of rosin. Another important class of nonionic surfactant comprises
multihydroxyl products such as glycol esters and poly glycerol esters. Specialty
surfactants such as silicone and ether crown surfactants have also been reported.

The most common nonionic surfactants are those based on ethylene oxide and are
prepared by the addition of ethylene oxide to carboxylic acid, primary or secondary
amines, alcohol or monoalkanolamide, or by the reaction of rosin acid with
polyethylene glycol (PEG) (Scheme 5.30) with different molecular weights to form
surfactants (N01-N06) [20].

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Rosin-based Chemicals and Polymers

Scheme 5.30 Synthesis of nonionic surfactants based on ethylene oxide (N01-N06)

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The hydroxyl group of rosin ester can also be esterified. Wei and co-workers reported
the synthesis of hydrogenated rosin-polyethylene glycol ester (N07) under microwave
irradiation (Scheme 5.31). The reaction time using microwave irradiation was shorter
than when the conventional heating method was used [51]. Then, the target product
hydrogenated rosin-polyethylene glycol-citric acid ester (N08) (Scheme 5.32) was
prepared by further esterification of the intermediate with citric acid. Wei and co-
workers reported the preparation of disproportionated rosin-polyethylene glycol ester
using the same method [52].

Scheme 5.31 Synthesis of hydrogenated rosin-polyethylene glycol ester (N07)

Scheme 5.32 Synthesis of hydrogenated rosin-polyethylene glycol-citric acid ester

(N08)

Sugar is a green, natural hydrophilic building block for surfactants and for this
reason, surfactants based on sugar are attracting a great deal of attention. Glucose
and sucrose were introduced into the skeleton of rosin by different kinds of reaction.
Xu and co-workers reported that glucose dehydroabietate (N09) was synthesised by
O-acylation of dehydroabietyl chloride with glucose in the presence of an ionic liquid
1-butyl-3-methylimidazolium bromide as a green reaction solvent (Scheme 5.33). The
catalyst could be recycled and used for three times [53]. Cen and co-workers reported

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that the acid chloride of rosin reacted with sucrose to form the corresponding ester
(N10) (Scheme 5.34) [54]. They also reported using rosin as the raw material for
the synthesis of rosin glycide diethanolamine propenoic acid sucrose ester (N11)
(Scheme 5.35) [55]. Mehltretter and co-workers reported that rosin amine reacted
with gluconolactone to form the corresponding glucose rosin nonionic surfactant
(N12) (Scheme 5.36) [56].

Scheme 5.33 Synthesis of glucose dehydroabietate (N09)

Scheme 5.34 Synthesis of rosin sucrose (N10)

Scheme 5.35 Synthesis of rosin glycide diethanolamine propenoic acid sucrose

ester (N11)

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Scheme 5.36 Synthesis of rosin amine gluconolactone (N12)

The hydrophilicity of glycerol is weak but it can be improved by polymerisation

reactions. Rosin-based polyglycerol (N13) nonionic surfactants with different degrees
of polymerisation of polyglycerol were obtained (Scheme 5.37) by an esterification
reaction [57]. Wang and co-workers reported that the nonionic surfactant polyglycerol
maleated rosin ester (N14) was synthesised by the reaction of maleated rosin and
polyglycerol (Scheme 5.38). The relationships between the surface physicochemical
properties of the product and the degree of polymerisation of polyglycerol were
studied systematically [58].

Scheme 5.37 Synthesis of rosin-based polyglycerol (N13)

Scheme 5.38 Synthesis of maleic rosin polyglycerol (N14)

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Specialty surfactants such as silicone surfactants can lower the surface tension of water
to below 20 mN/m. Silicone surfactants are sometimes referred to as ‘superwetters’
as they cause enhanced wetting and spreading in aqueous solution [59]. However,
they are much more expensive than conventional surfactants and are only used for
specific applications for which low surface tension is a desirable property. Silicone-
modified rosin-based surfactants (N15) can be synthesised from rosin acid chloride
(Scheme 5.39) [20].

Scheme 5.39 Synthesis of silicone modified rosin (N15)

Azacrown ethers are new functional compounds. They have specific surface activities,
catalytic activities, complex selectivity and good adsorption properties for many heavy
or precious metal ions. Yang and co-workers [60] reported the synthesis of three
chiral azacrown ethers from rosin: N-dehydroabietyl monoaza-15-crown-5 (N16),
N-dehydroabietyl monoaza-18-crown-6 (N17) and N-nor-dehydroabietyl monoaza-
12-crown-4 (N18) (Scheme 5.40). Dehydroabietylamine and nor-dehydroabietylamine
can react with ether diiodide to form the corresponding azacrown ethers. Hydroxyl
derivatives of rosin reacted with tosylate to form the corresponding azacrown ethers.
The azacrown ethers can be employed as phase transfer catalysts in the asymmetric
Michael addition of 2-nitropropane to chalcone.

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Scheme 5.40 Synthesis of chiral azacrown ethers (N16-N18)

5.3 Physicochemical Properties

5.3.1 Physical Properties

The physical properties of rosin-based surfactants change significantly when different

hydrophilic groups are attached to the rosin skeleton [1]. The most important change
is their critical micelle concentration (CMC) and surface tension at critical micelle
concentration (δCMC) values. Each surfactant molecules has a characteristic CMC at
a given temperature and electrolyte concentration. The most common technique for
measuring the CMC is by determining the surface tension.

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Table 5.1 lists some of the physical properties of cationic rosin-based surfactants.
Their surface activities were compared with that of the widely used cationic surfactant,
benzalkonium bromide. The CMC values of most cationic quaternary ammonium
compounds such as C01-C04 are between 10-4-10-3 mol/L with δCMC values between
32-50 mN/m. However, the rosin-based cationic gemini surfactants, such as C06,
C25-C28, exhibited lower CMC values, which were near 10-5 mol/L with δCMC values
between 23-31 mN/m. Gemini surfactants had a low δCMC and CMC value, and the
CMC of these was about two orders of magnitude lower than the corresponding
conventional surfactants with the same alkyl chain length.

Table 5.1 Physical properties of rosin based cationic surfactants

δCMC(25
CMC FP(0/5min) EP
Surfactants °C) KP (°C)
(mol/L) mm (Benzene)
(mN/m)
C01 35-36 5×10-3 — — —

C02 38-39 5×10-3 — — —

C03 40-42 5×10-3 — — —

C04 40-42 5×10-3 — — —

C05 — 7.85×10-3 — 16 s —

C06 26.4 3.1×10-5 45/40 5d 28

C09 45.0 2.7×10-4 89/54 30 s 60-65

C10 34.9 1.0×10-4 — — —

C11 37.5 5.3×10-4 85/65 2480 s ＞90

C12 49.5 1.1×10-3 20/0 5d —

C14 37.3 4.02×10-3 — — ＜0

C15 34.1 3.61×10-3 110/0 1.5 m 13

C16 33.2 3.45×10-3 125/40 10 m <0

C17 36.0 — 100/0 1m 75

C18 32.7 1.70×10-3 140/90 20 m <0

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 Synthesis and Application of Rosin-Based Surfactants

C19 32.5 1.1×10-3 155/98 25 m <0

C20 35.0 3.3×10-3 135/60 17 m <0

C25 30.3 2.6×10-5 20/15 4d 90

C26 28.8 5.5×10-5 25/5 50 m >100

C27 27.1 2.7×10-5 70/2 2m >100

C28 23.7 2.0×10-5 40/2 4d >100

Benzalkonium
34.0 7.8×10-3 165/157 17 m <0
bromide
CMC - Critical micellisation concentration
δCMC - Surface tension of surfactant at the concentration of CMC
EP - The ability of a surfactant to form emulsions between two solutions ordinarily
insoluble in each other
FP - The ability to produce foam, and foam stability
KP - Krafft point
HLB - Hydrophilic-lipophilic balance
d - day
m - minute
s - second
Data adapted from references [12, 13, 19-23, 28, 30]

Table 5.2 shows the physical properties of some rosin-based anionic surfactants, and
their surface activities were compared with that of widely used anionic surfactant
of sodium dodecyl sulfate (K12) and alcohol ether sulfate (AES). The δCMC of most
anionic surfactants were between 24 and 40, and their CMC values were between
10-4-10-3 mol/L. Rosin-based anionic gemini surfactants also showed better CMC
and δCMC values than conventional ones.

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Rosin-based Chemicals and Polymers

Table 5.2 Physical properties of rosin based anionic surfactants

δCMC(25 °C) CMC FP (0/5min)/ EP

Surfactants KP (°C)
(mN/m) (mol/L) mm min

A06 50.63 24.5×10-3 — — —

A07(n=5) 36.5 6.1×10-3 130/90 14 <0
A07(n=10) 37.5 3.3×10 -3
130/90 17 <0
A07(n=19) 41.0 1.4×10-3 115/20 21 <0
A08(n=6) 33.1 6.2×10 -3
138/135 10 <0
A08(n=10) 34.2 4.4×10-3 132/129 89 <0
A08(n=20) 37.0 2.1×10 -3
129/124 85 <0
A09(n=9)) 38.2 5.3×10-3 112/109 17 <0
A10(n=10) 39.7 — 120/10 10 <0
A11 24.74 0.8×10 -3
145/145 9 —
A15 — 1.1×10-4 — — <0
A16 — 1.6×10 -4
— — <0
A17(n=2) 31.0 3.2×10-4 2/0 20 <0
A17(n=4) 28.6 2.9×10 -4
2/0 30 <0
A17(n=6) 29.4 1.8×10-4 60/40 60 <0
A17(n=8) 28.1 1.3×10-4 2/0 20 <0

K12 33 8.1×10-3 175/170 12 10

AES 28 3.7×10-3 175/168 13 <0

K12 - sodium dodecyl sulfate

AES - alcohol ether sulfate

Data adapted from references [20, 35-37, 40]

Table 5.3 shows the physical properties of some rosin based zwitterionic surfactants.
The δCMC of most zwitterionic surfactants were between 24 and 40, and their CMC
values were near 10-3 mol/L.

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 Synthesis and Application of Rosin-Based Surfactants

Table 5.3 Physical properties of rosin based zwitterionic surfactants

δCMC(25 °C) CMC FP(0/5 min)
Surfactants EP min KP (°C)
(mN/m) (mol/L) mm
Z01 21.3 1.39×10-3 — — —
Z02 31.91 3.16×10 -3
— — —
Z03 33.20 3.01×10-3 — — —
Z04 25.79 2.56×10-3 — — —
Z06 — 5.16×10-3 88/81 13 —
Z07 53.25 9×10-1 — — —
Z09 35.0 2.0×10 -3
150/90 1.5 <0
Z10 36.5 1.3×10-3 130/60 2.0 <0
Data adapted from references [20, 35-37, 40]

Table 5.4 shows the physical properties of some rosin based nonionic surfactants.
The δCMC of most anionic surfactants are near 40, and their CMC values are near
10-3 mol/L. Rosin-based nonionic surfactants with different degree of polymerisation
were investigated in detail and the results showed that their CMC values were near
10-4 mol/L and the δCMC values were between 32-40 mN/m.

5.3.2 Phase Behaviour

The theoretical study of rosin-based surfactants has attracted little attention in

recent years. Compared with fatty acid as a hydrophobic group, the tricyclic
hydrophenanthrene structure may show different phase behaviour.

Persson and co-workers investigated [61] the phase behaviour of two rosin-
based nonionic surfactants, polyoxyethy1ene dehydroabietates (DeHAb(EtO))
with polyoxyethylene chains of 11 and 22, in water and decanol system (Figure
5.1). DeHAb(EtO)11 is completely miscible with water but has a low capacity for
solubilisation of decanol. However, at DeHAb(EtO)22 surfactant concentrations of
0-25%, the maximum solubilisation capacity for decanol represents a nearly constant
ratio between the amount of solubilisate and surfactant. The results showed that
the two rosin-based surfactants behave similarly to nonionic surfactants with a
hydrophobic aliphatic carbon chain and a polyethylene oxide chain as the hydrophilic
group. However, the acyclic surfactant has a good solubilising capacity for most

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Rosin-based Chemicals and Polymers

compounds. In both systems, a lamellar liquid crystalline phase is formed, indicating

that the surfactants have lamellar structures in the system.

Table 5.4 Physical properties of rosin based nonionic surfactants

δCMC(25 °C) FP(0/5min) EP TP
Surfactants CMC (mol/L) HLB
(mN/m) min min (°C)
N01(n=10) 34.6 2.9×10-4 45/39 4.8 59 11.0

N01(n=19) 36.4 4.5×10-4 82/76 4.6 77 14.9

N02(n=10) 32.7 1.0×10-4 80/77 5.3 >10 —

N02(n=20) 35.1 2.4×10-4 80/76 5.3 0 —

N03(n=9) 35.0 2.3×10-4 78/76 4.8 71 —

N04(n=10) 36.8 — 80/74 4.9 46 —
N05-200 37.7 — >150 — — —
N05-1000 37.6 — 25.8 80 — —
N07 42.0 — 18.5/— — — —
N08 41.5 — 17/— — — —
N10 50.1 — — — — —
N11 22.9 9×10 -3
— — — —
8.4×10-4- 44-
N13 44.2-49.6 6-46/ — —
2.6×10-3 85
9.4×10-4- 38-
N14 39.9-46 11-65/ — —
2.2×10-3 100
C12EO(n=10) 37.0 — 140/100 — 53 13.9
TP – Cloud point
Data adapted from references [20, 51, 52, 54, 55, 57, 58]

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 Synthesis and Application of Rosin-Based Surfactants

0 100 0 100

25 ˚C 25 ˚C

r
we

we
te

te
wa

wa
igh

igh
%

%
t%

t%
t

t
igh

igh
de

de
we

we
c

c
an

an
L

ol

ol
L
LC
LC
100 0 100 0
0 weight % DeHAb(E10) 100 0 weight % DeHAb(E10) 100
11 22

Figure 5.1 Phase diagram for the three-component water-surfactant-decanol

system. Reproduced with permission from M. Persson, P. Stenius, G. Strom, L.
Odberg, I. Oimgren, Journal of Physical Chemistry, 1980, 84, 1557. ©1980,
American Chemical Society [61]

Jiang and co-workers [62] reported that critical aggregation numbers of micelles
(N) of rosin-modified quaternary ammonium gemini surfactants (C25-C27) were
determined by a steady-state fluorescence probe method. The results showed that N
increased linearly with the increase of the surfactant concentration in a range of 5-15
times CMC and critical aggregation numbers of micelle (Nm) can be extrapolated
from the N—C curve, which were 10, 19, and 20 for C25, C26 and C27 respectively.

5.4 Applications

5.4.1 Paper Sizing and the Rubber Industry

Rosin acids are tacky solids at room temperature. Saponify the rosin by addition
of base so that it becomes soluble in water and it then can be added effectively to a
paper machine. Different industries use gum rosin in varying amounts as is indicated
in Figure 5.2. Soap production, paper making and the synthetic rubber industry
consume large amounts of rosin [63].

159
Rosin-based Chemicals and Polymers

Printing 3.7% Rubber 4.8%

Coating 12.9%

Soap 43.9%

Paper making 35.2%

Figure 5.2 Gun rosin usage in industry, the data adapted from reference [63]

Most rosin soaps have water-loving carboxylate groups, and the remainder of the
rosin molecule has a water-hating hydrocarbon group. The rosin soap exists as
micelles in solution, and the groups of soap molecules associate with each other so
that the water-hating parts face each other to avoid contact with water. Aluminum
compounds are needed for paper making furnish. Aluminum ions react with the
carboxylate groups in the rosin, which causes the rosin to precipitate on to the fibre
surface. The recommended pH conditions for rosin soap sizing are dictated by the
effect of pH on the predominant species of the aluminum ions. Low pH conditions
favour the presence of trivalent aluminum, a hydrated form of Al3+. This is the species
that appears to be most useful for the retention and setting of rosin soap size [64].

Rosin soaps are designed for use as an emulsifier in the polymerisation of styrene-
butadiene rubber and other synthetic rubbers. It was used for the polymerisation
of styrene-butadiene rubber emulsifiers. When dispersed in the aqueous phase of
the monomer emulsion they facilitate micelle formation, thereby forming stable
monomers. Rosin calcium soap is used in paints. Lead, cobalt and manganese have
been used traditionally as driers in these paints.

5.4.2 Antibacterial Activity

The antibacterial activity of rosin-based surfactants has been mostly focused on

cationic surfactants (quaternary ammonium salts). Quaternary ammonium salts
are frequently used as antibacterial agents because they can disrupt cell membranes

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 Synthesis and Application of Rosin-Based Surfactants

through the binding of their ammonium cationic groups to anionic sites in the
outer tissue layers of bacteria [65]. As a result of the combination of their tricyclic
hydrophenanthrene structure and quaternary ammonium group, rosin-based cationic
surfactants exhibit good antibacterial activity.

Quaternary ammonium salts (C01-C04) were tested by the standard procedures of

measuring the zone of microorganism growth suppression. Their activities were similar
to widely used biocides, such as triclosan, aeseptodin and biopag-2. They exhibited
strong antibacterial and antifungal activities [12].

Wang and co-workers reported that six dehydroabietylamine-based cationic

surfactants exhibited antibacterial activity against Staphylococcus aureus (S. aureus)
and Escherichia coli. The activity of C16 against S. aureus is similar to that of
benzalkonium bromide; the minimum inhibitory concentration (MIC) reached 7.81
μg/mL [28].

Jia and co-workers reported that N,N,N′,N′-tetramethyl N,N′-diethanolamine

dehydroabietate diamine dibromide and N,N,N′,N′-tetramethyl N,N′-
didehydroabietate diamine dibromide had antibacterial activity against E. coli,
Klebsiella pneumoniae (K. pneumoniae), Enterobacter aerogenes (E. aerogenes), S.
aureus, Staphylococcus epidermidis (S. epidermidis), Pseudomonas aeruginosa (P.
aeruginosa), and Salmonella typhi (S. typhi). In particular, N,N,N′,N′-tetramethyl
N,N′-diethanolamine dehydroabietate diamine dibromide showed marked
antibacterial activities against E. aerogenes, S. aureus, S. epidermidis and P. aeruginosa;
the minimum inhibotory concentrations were 16-64 μg/mL [66].

Cai and co-workers reported that antibacterial activity of 3-dehydroabietylamino-2-

hydroxypropyl trimethylammonium chloride (DHAHPTMA) (C32) was evaluated
according to its minimum inhibitory concentrations against S. aureus, S. epidermidis,
Clostridium perfringens, K. pneumoniae, E. coli, P. aeruginosa and Salmonella.
The results (Figure 5.3) indicated that DHAHPTMA exhibited good antibacterial
activity; the minimum inhibotory concentrations of DHAHPTMA against S. aureus,
S. epidermidis and E. coli were lower than that of bromo-geramium and higher than
ofloxacin against theses bacteria [32].

161
Rosin-based Chemicals and Polymers

140
C32
120 Ofloxacin
Bromo-geramium
100

80
MIC (µg/mL)

60

40

20

0
S. aueus S. epidemidis C. perfringens K. pneumonice E. coli P. aeruginosa S. almonella

Bacterium

Figure 5.3 Antibacterial activity of (C32) compared with bromo-geramium and

ofloxacin, the data adapted from reference [32]

5.4.3 Corrosion Inhibition

Inhibition of metal corrosion by organic compounds is a result of the adsorption of

organic molecules or ions at the metal surface forming a protective layer. This layer
reduces or prevents corrosion of the metal. The extent of adsorption depends on the
nature of the metal, the metal surface condition, the mode of adsorption, the chemical
structure of the inhibitor, and the type of corrosion medium [67].

Rosin-based cationic surfactants exhibited corrosion inhibition activity. Wang and

co-workers reported [28] their corrosion inhibition activities against steel, which were
investigated in hydrochloric acid solution by the weight loss method. Six kinds of
cationic surfactants which acted as corrosion inhibitors are listed in Table 5.5. Most
of them exhibited higher activity than benzalkonium bromide. The inhibition ratio
reached 99.1% for C20 compared with 93.0% for benzalkonium bromide.

Rosin-based nonionic surfactants also exhibited anticorrosion activity. A series of N,N-

polyoxyethylene dehydroabietylamines (N02) with different numbers of oxyethylene
units (n) were used as corrosion inhibitors for metals (Table 5.5) [20]. The relationships
between performance and chemical structure of the products were investigated. The
corrosion inhibition activities of the rosin-based nonionic surfactants with fewer
than 20 ethylene oxide units were higher than that of benzalkonium bromide. The
inhibition rate reached 95.1% for surfactants with 15 ethylene oxide units. However
the hydroxyl amides of rosin acids (N03) had a little lower activity than the above
products, and their inhibition activity was equal to that of benzalkonium bromide.

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 Synthesis and Application of Rosin-Based Surfactants

Table 5.5 Corrosion inhibition of some rosin-based cationic surfactants

Surfactants Corrosion rate (mm/year) Corrosion inhibition rate (%)
Blank 17.83 —
C15 0.25 98.6
C16 1.57 91.2
C17 0.30 98.3
C18 1.07 94.0
C19 0.48 97.5
C20 0.16 99.1
N02(p+q=6) 1.212 93.2
N02(p+q=10) 0.945 94.7
N02(p+q=15) 0.874 95.1

N02(p+q=20) 1.337 92.5

N03(n=4) 1.23 93.1

N03(n=6) 1.09 93.9
N03(n=9) 1.28 92.8
N03(n=14) 1.41 92.1
N03(n=16) 1.76 90.1
Benzalkonium
1.25 93.0
bromide
n, p and q are degrees of polymerisation
Data adapted from references [20, 28]

5.4.4 Chiral Catalyst

The majority of uses of rosin-based surfactants are in paper sizing agent, as a rubber
emulsifier and as antibacterial agents. The uses of diterpene resin acids as convenient
chiral pools for the synthesis of chiral ligands suitable for metallocomplex catalysts
of asymmetric reactions have been studied [68] but, so far, there have been few
applications in this field. The use of pine resin acids as chiral pools would also be
useful for the preparation of chiral surfactants.

163
Rosin-based Chemicals and Polymers

Pan and co-workers reported [29] using four novel chiral quaternary ammonium
salts (C21-C24) synthesised from dehydroabietylamine as phase transfer catalysts in
asymmetric epoxidation reactions of chalcone (Scheme 5.41). The results indicated
that chalcone cannot be oxidised by sodium chlorate or hydrogen peroxide without
catalysts in several days. However the reaction could occur in the presence of a
rosin-based chiral catalyst. The structure and amount of catalyst affected the reaction
greatly. The catalyst that contained benzene groups at the head greatly accerated
the reaction procedure, with higher selectivity compared to a catalyst with an alkyl
group. They afforded the corresponding epoxides in high yields and up to 20%
enantiomeric excess (ee) [69].

Scheme 5.41 Rosin based cationic surfactant as phase transfer catalyst

Yang and co-workers used [60] three chiral azacrown ethers, i.e., N-dehyroabietyl
monoaza-1,5-crown-5,  N-dehyroabietyl monoaza-1,8-crown-6 and  N-degrading-
dehyroabietyl monoaza-12-crown-4 [N16-N18] synthesised from rosin as phase
transfer catalysts in the asymmetric Michael addition of 2-nitropropane to chalcone
(Scheme 5.42). This afforded the corresponding Michael addition products with up
to 35% ee value. Three kinds of rosin-based chiral azacrown ethers can catalyse
chalcone Michael addition reactions. The yield is about 43-51% and the ee value
reached 35% with the best catalyst activity. The structure of the azacrown ether greatly
affected the selectivity of the catalyst reactions. These chiral azacrown ethers can also
catalyse epoxidation reactions of chalcone, and the yield of products reached 47-69%.
However, these catalysts almost have no selectivity to form enantiomeric products.

Scheme 5.42 Chiral azacrown ethers as phase transfer catalysts in asymmetric

Michael addition

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 Synthesis and Application of Rosin-Based Surfactants

5.4.5 Chiral Separation

Because there are many chiral carbon atoms in the pine resin acids and their
derivatives, they have been widely used in the separation technology. Pine resin acids
and amines are used as chiral reagents for the resolution of isomers of biological
compounds. For example, dehydroabietic acid is used as a reagent for separating
chiral amines and dehydroabietylamine is used as a reagent to separate chiral acids.
These separation reactions usually depend on salt formation reactions, and according
to their solubility in organic solvents, resolution of the biological isomers can be
obtained by recrystallisation. With the development of separation technology, micellar
electrokinetic chromatography (MEKC), as an electrokinetic separation technique
[70], has become one of the most popular techniques in the field of separation science
due to its high resolving power and capability of separating both ionic and neutral
compounds. One of the attractive applications of MEKC is enantiomer separation
[71]. In MEKC, chiral surfactants have been used as a pseudostationary phase for
chiral separation. Rosin is a naturally occurring enantiomeric diterpenic acid, which
is an excellent starting material for preparing chiral surfactants because of its wide
availability and special stereostructure.

Wang and co-workers reported [33] a new type of anionic chiral surfactant (SMA,
[A02, see Scheme 5.16]), which was used for the enantioselective MEKC separation of
amino acid enantiomers derivatised with naphthalene-2,3- dicarboxaldehyde (NDA-
d/l-AA). Under the conditions selected, two pairs of tested amino acid enantiomers,
including NDA-d/l-trptophan and NDA-d/l-kynurenine were resolved. On the other
hand, SMA showed high aqueous solubility and low CMC, which simplified the
MEKC methodology, and avoided the use of a comicellar phase system and organic
solvents for chiral separation [33].

Zhao and co-workers reported [49] a new type of zwitterionic chiral surfactant,
DHAMAP, (Z10, see Scheme 5.28) which was used to perform chiral separation
of d/l-amino acids by capillary electrophoresis (CE). Six pairs of tested amino acids
enantiomers including NDA-d/l-tryptophan (NDA-d/l-Trp), NDA-d/l-phenylalanine
(NDA-d/l-Phen), NDA-d/l-kynurenine (NDA-d/l-Kyn), NDA-d/l-β-phenylalanine
(NDA-d/l-β-Phen), NDA-d/l-4-methylphenylalanine (NDA-d/l-4-M-Phe) and NDA-
d/l-arginine were well-resolved (Figure 5.4). All compounds were fully separated
by using a chiral running buffer consisting of a rosin-based surfactant DHAMAP.
However, separation was not obtained if the running buffer did not contain DHAMAP.
DHAMAP is an amphoteric chiral surfactant; alterations of buffer pH can affect
the charge on the analyte and the chiral pseudophase, thus influencing the chiral
separation.

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Rosin-based Chemicals and Polymers

10

L-β-phe

D-Kyn
D-Trp

L-Kyn
8

D-β-phe

L-Trp
6
4
2
mAU

0
–2
–4
–6
–8
0 5 10 15 20 25
t/min

Figure 5.4 Electropherogram for the enantiomeric separation of a mixture of three

NDA-d/l-amino acids (i.e. NDA-d/l-β-Phen, NDA-d/l-Trp and NDA-d/l-Kyn).
Reproduced with permission from S.L. Zhao, H.S. Wang, Y.M. Pan, M. He, Z.C.
Zhao, Journal of Chromatography A, 2007, 1145, 246. ©2007, Elsevier [49]

The advantages of rosin-based surfactants as a chiral surfactant for the separation

of amino acids are that the tricyclic hydrophenanthrene structure contains many
chiral centres, the synthetic procedure for the surfactants is relatively simple and the
starting material is a natural product which easily available.

5.4.6 Material Synthesis

The ability of surfactants to self-assemble into well-defined structures has been taken
advantage of for the design and synthesis of inorganic materials with nanosized
dimensions [72]. This approach to nanomaterials preparation has triggered substantial
interest both in the surface chemistry and the materials chemistry community. In
the previous research, surfactants have been used as templates in the synthesis of
nanoinorganic powder materials, nanostructured materials, nanocomposite materials
and Langmuir-Blodgett films. The size, charge, and shape of the surfactant are
important structure-determining parameters in the synthesis of the materials.

As special structure surfactants, rosin-based surfactants may be used to synthesise

inorganic materials. Han and co-workers reported [73] that nickel hydroxide materials
were prepared by a microwave solvothermal method with a rosin-based surfactant

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 Synthesis and Application of Rosin-Based Surfactants

(referred to as S1 but no structure was given [73]). Nickel hydroxide coral-like

microspheres with a diameter of 2 μm were synthesised by using S1 surfactant. It was
shown that these microspheres were assembled from nanosheets with a thickness of 30
nm and a width of 2 μm. The homogeneous size and uniform appearance of the nickel
hydroxide materials could be controlled through the addition of S1. The micelles of
surfactant made the foam stable, which was better for the formation of nuclei for the
nickel hydroxide particles and, at the same time, the micelles of surfactant ensured
that the nickel hydroxide particles were well-dispersed in the reaction system. Due to
the special stereostructures and easily availability of rosin-based surfactants their use
for the synthesis of, and applications for, nanomaterials may attract more and more
attention, because those surfactants can act as templates for nanostructured materials.

5.5 Development Trends of Rosin-Based Surfactants

The surfactant industry is facing an important challenge, with growing environmental

concerns over the issues of biodegradability, pollution control in manufacturing
processes, and consumer desire for ‘green’ ingredients and products. The development
of ‘green’ surfactants based on natural renewable resources is a concept that is gaining
recognition in fundamental research and applications. There are many advantages of
using natural-based products as raw materials for surfactant applications compared
to petroleum-based raw materials. With the increasing amount of pine forestry that
can be tapped, the output of rosin will increase more and more. Natural products
offer unique special structural elements in the surfactant molecule, which make the
surfactants exhibit unique chemical physical properties. Surfactants based on natural
starting materials can often be made more biodegradable, less toxic and less allergenic.
As natural-based fine chemicals, rosin-based surfactants will attract more and more
attention, not only because of the large quantity of product of raw material which
is available, but also because of the special stereostructures which they contain.
Traditional rosin-based surfactants have been investigated and applied widely in past
years. However, as we know, no single kind of surfactant can be used in industry. It is
often necessary to use several kinds of surfactants together, so the usage of rosin-based
surfactants with other surfactants, or different kinds of rosin-based surfactants used
together, should be paid more and more attention. Traditional rosin-based surfactants
are commonly used for industrial applications, such as paper sizing, in the rubber
industry, as antibacterial and antifungal agents, and as corrosion inhibitors. New
application fields of rosin-based surfactants need to be researched. Focusing on the
special structure of rosin-based surfactants, their uses as chiral catalysts, for chiral
separation and for the synthesis of nanomaterials will represent a new trend in future
research because little work has been done in these fields.

167
Rosin-based Chemicals and Polymers

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