WO2022157368A1

WO2022157368A1 - Lubricant additive

Info

Publication number: WO2022157368A1
Application number: PCT/EP2022/051508
Authority: WO
Inventors: Nicholas David Spencer; Tobias Alexander GMÜR; Joydeb Mandal; Stefan Zürcher
Original assignee: Nicholas David Spencer
Priority date: 2021-01-22
Filing date: 2022-01-24
Publication date: 2022-07-28

Abstract

The invention relates to a block copolymer compound comprising an oleophilic block comprising first repeat units having C_6-24 alkyl side chains, and a surface-anchoring block comprising second repeat units bearing side chains conducive to the attachment to a solid surface that comprise aliphatic or aromatic hydroxy (-OH) or amine (-NH _n R₂ _- _n) moieties. The invention further relates to the use of the block copolymer compound of the invention as a lubricating additive, and to a composition comprising the block copolymer compound of the invention and a base oil.

Description

Lubricant Additive

The present invention relates to block copolymers comprising or consisting of one or several polymer blocks of oleophilic repeat units and at least one polymer block of repeat units comprising repeat units with surface-anchoring side chains, of which nitrodopamine- terminated side chains are one example, and amine-terminated side chains are another. The invention further relates to the use of the block copolymers according to the invention as an additive in lubricating-oil compositions, and to compositions comprising the additive copolymer according to the invention.

Background of the Invention

Most industrial machinery and all engines involve the sliding and/or rolling of steel components against each other. In order to lower power loss and energy wastage via friction, as well as reducing wear, such contacts are lubricated, generally by a lubricating oil. Such oils consist of a base oil (generally hydrocarbon) and additives, which serve a number of purposes, including foam inhibition, viscosity modification, wear prevention and friction reduction. In an effort to reduce energy consumption of vehicles, in particular, modern lubricating oils have increasingly been formulated at lower viscosities. This means that the sliding and/or rolling parts are not so efficiently held apart by viscous forces, and more likely to spend time in the "boundary" regime, i.e. in close contact, where protruberences ("asperities") on both sliding surfaces actually touch each other, leading to higher friction and wear. This increases the demands on lubricant additives that lower friction and reduce wear. There are a number of effective friction-reducing additives that are commonly used in lubricants but every improvement in additive effectiveness corresponds to savings in energy, which in the case of transportation applications directly translates to an increase in range per tank of fuel or, in the case of electric vehicles, range per charge.

There have been many attempts at dealing with the "oiliness" of lubricating oils. This concept is normally regarded as the quality of the oil that makes them slippery to the feel, i.e. lowering friction at low sliding speed (boundary lubrication). Historically, long-chain fatty acids were used as friction modifiers to this end (Spikes, H. Friction Modifier Additives. Tribol Lett 60, 5 (2015). https://doi.org/10.1007/s11249-015-0589-z), oleic acid being a prime example. Additionally, esters, amines, amides and alcohols have been used. A particularly effective member of the latter class is glycerol monooleate, which is probably more effective due to its two binding sites, rather than a single site in the case of oleic acid, for example.

Polymer additives have been extensively used for a different purpose, namely as viscosityindex improvers (VII) (Martini, A., Ramasamy, U.S., Len, M.: Review of Viscosity Modifier Lubricant Additives. Tribol. Lett. 66, 1-14 (2018)). These are intended to change the viscosity of the oil with temperature, so that the viscosity remains more constant than it would for the base oil. This has the result of reducing energy consumption during cold starts. VI Is have been prepared as block copolymers, and often contain polar blocks. Such additives have been shown to reduce friction at low speeds (i.e. function as boundary lubricants, as does the present invention) but they do this by forming a thicker elastohydrodynamic film (Cann and Spikes, Tribol. Trans. 37, 580-586 (1994); Muller et al. Tribol. Trans. 49, 225-232 (2006). Fan et al., Tribol. Lett. 28, 287-298 (2007)) (see also Dardin US8288327, Zhao US10414998). There is another important difference: Many of the Vlls that work as boundary lubricants typically only do so at very high concentrations of 10-30 wt.%. This is because the interaction with the surface is weak and dynamic, i.e. there is constant desorption and adsorption taking place. The present invention is highly effective at 0.5 wt%, and has been demonstrated to form a strong attachment to the surface.

There are other patented block-copolymer friction modifiers that seem mostly to be effective in polar media, which is not the topic of this invention. (Thompson US 9228152B2)

W02016037630A1 (published also as US2017291971A1 , incorporated by reference) teaches the synthesis of polymer blocks comprising or consisting of acrylate N-(nitrodopamine) amide.

Based on the above-mentioned state of the art, the objective of the present invention is to provide a lubricant additive improving on the previously outlined disadvantages. This objective is attained by the subject-matter of the independent claims of the present specification, with further advantageous aspects and embodiments provided in the dependent claims, and other examples, items and particular embodiments provided herein.

Summary of the Invention

In one aspect, the invention relates to a block copolymer compound comprising, or essentially consisting of, two types of blocks: an oleophilic block interacting with a base lubricant, and a surface-anchoring block that attaches the block copolymer to a surface of a component in need of lubrication.

An oleophilic block of the block copolymer according to this aspect of the invention comprises, or essentially consists of, a polymer of first repeat units comprising linear or branched Ce-24 alkyl side chains.

A surface-anchoring block of the block copolymer according to this aspect of the invention comprises, or essentially consists of, second repeat units bearing side chains conducive to the attachment to a solid surface. Non-limiting particular examples of second repeat units that are comprised in, or constitute, the surface-anchoring block are repeat units bearing side chains comprising one or several amino, carboxyl, R>-keto-carboxyl, amide, hydroxamate, aliphatic or aromatic hydroxy, phosphate or a phosphonate alkyl ester, thiol, thioalkylether, alkylsilylether, chlorosilane, carbene, perfluorophenyl azide or benzophenone, diaryldiazomethane or organoboron moieties.

A second aspect of the invention relates to the use of the block copolymer according to the invention as a friction-reducing additive in a lubricating composition. Alternatively, or additionally, the additive can be used, as part of a lubricating composition, to reduce wear of the lubricated components.

A third aspect of the invention relates to a lubricant composition containing a block copolymer according to the invention and non-polar base oil.

The lubricant additive according to the present invention demonstrably reduces the friction further (i.e. saves more energy) than alternatives, such as glycerol mono-oleate. It can also contribute to the lubricant’s performance by reducing wear.

Terms and definitions

For purposes of interpreting this specification, the following definitions will apply and whenever appropriate, terms used in the singular will also include the plural and vice versa. In the event that any definition set forth below conflicts with any document incorporated herein by reference, the definition set forth shall control.

The terms “comprising,” “having,” “containing,” and “including,” and other similar forms, and grammatical equivalents thereof, as used herein, are intended to be equivalent in meaning and to be open ended in that an item or items following any one of these words is not meant to be an exhaustive listing of such item or items, or meant to be limited to only the listed item or items. For example, an article “comprising” components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. As such, it is intended and understood that “comprises” and similar forms thereof, and grammatical equivalents thereof, include disclosure of embodiments of “consisting essentially of” or “consisting of.”

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit, unless the context clearly dictate otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the disclosure, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the disclosure. Reference to “about” a value or parameter herein includes (and describes) variations that are directed to that value or parameter per se. For example, description referring to “about X” includes description of “X.”

As used herein, including in the appended claims, the singular forms “a,” “or,” and “the” include plural referents unless the context clearly dictates otherwise.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of tribology, lubricants and their additives. Textbooks covering the topic include H. Prashad: Solving Tribology Problems in Rotating Machines (1st Edition) Woodhead Publishing 2006, ISBN 9781845691103; Mang, and Dresel (Eds.): Lubricants and Lubrication, 3^rd. Edition, Wiley VCH 2017, ISBN: 3527326707; Ludema and Ajayi: Friction, Wear, Lubrication, Taylor and Francis 2018, EAN 9780429815911 ; Daschner and Webster: Lubrication Fundamentals, Revised and Expanded, Taylor and Francis 2017, EAN 9781315359908.

The term oleophilic in the context of the present specification relates to the solubility of the polymer or polymer block in oil-like or hydrocarbon-based solvents, such as mineral oils. It can be regarded as a synonym of lipophilic and an antonym of oleophobic. Oleophilic polymers themselves generally consist largely of hydrocarbon species, although minor quantities of oxygen or nitrogen atoms can be compensated by a larger number of C-H groups, so as to lead to solubility in hydrocarbon-based solvents.

The term C1-C4 alkyl in the context of the present specification relates to a saturated linear or branched hydrocarbon having 1 , 2, 3 or 4 carbon atoms, wherein in certain embodiments one carbon-carbon bond may be unsaturated and/or one CH2 moiety may be exchanged for oxygen (ether bridge) or nitrogen (NH, or NR with R being methyl, ethyl, or propyl; amino bridge). Nonlimiting examples for a C1-C4 alkyl are methyl, ethyl, propyl, prop-2-enyl, n-butyl, 2- methylpropyl, tert-butyl, but-3-enyl, prop-2-inyl and but-3-inyl. In certain embodiments, a C1-C4 alkyl is a methyl, ethyl, propyl or butyl moiety.

A Ci-Ce alkyl in the context of the present specification relates to a saturated linear or branched hydrocarbon having 1 , 2, 3, 4, 5 or 6 carbon atoms, wherein one carbon-carbon bond may be unsaturated and/or one CH2 moiety may be exchanged for oxygen (ether bridge) or nitrogen (NH, or NR with R being methyl, ethyl, or propyl; amino bridge). Non-limiting examples for a Ci-Ce alkyl include the examples given for C1-C4 alkyl above, and additionally 3-methylbut-2- enyl, 2-methylbut-3-enyl, 3-methylbut-3-enyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 1 ,1- dimethylpropyl, 1 ,2-dimethylpropyl, 1 ,2-dimethylpropyl, pent-4-inyl, 3-methyl-2-pentyl, and 4- methyl-2-pentyl. In certain embodiments, a C5 alkyl is a pentyl or cyclopentyl moiety and a Ce alkyl is a hexyl or cyclohexyl moiety. The term C4-C7 cycloalkyl in the context of the present specification relates to a saturated hydrocarbon ring having 4, 5, 6 or 7 carbon atoms, wherein in certain embodiments, one carbon-carbon bond may be unsaturated and/or one CH2 moiety may be exchanged for oxygen (ether bridge) or nitrogen (NH, or NR with R being methyl, ethyl, or propyl; amino bridge). Nonlimiting examples of a C4-C7 cycloalkyl moiety include cyclobutyl (-C4H7), cyclopentenyl (C5H9), and cyclohexenyl (CeHn) moieties. In certain embodiments, a cycloalkyl is substituted by one Ci to C4 unsubstituted alkyl moiety. In certain embodiments, a cycloalkyl is substituted by more than one Ci to C4 unsubstituted alkyl moieties.

The term unsubstituted C_n alkyl when used herein in the narrowest sense relates to the moiety -C_nH2n- if used as a bridge between moieties of the molecule, or -C_nH2n+i if used in the context of a terminal moiety. It may still contain fewer H atoms if a cyclical structure or one or more (non-aromatic) double bonds are present.

The term C_n alkylene in the context of the present specification relates to a saturated linear or branched hydrocarbon comprising one or more double bonds. An unsubstituted alkylene consists of C and H only. A substituted alkylene may comprise substituents as defined herein for substituted alkyl.

The terms unsubstituted C_n alkyl and substituted C_n alkyl include a linear alkyl comprising or being linked to a cyclical structure, for example a cyclopropane, cyclobutane, cyclopentane or cyclohexane moiety, unsubstituted or substituted depending on the annotation or the context of mention, having linear alkyl substitutions. The total number of carbon and -where appropriate- N, O or other hetero atom in the linear chain or cyclical structure adds up to n.

Where used in the context of chemical formulae, the following abbreviations may be used: Me is methyl CH3, Et is ethyl -CH2CH3, Prop is propyl -(CFk^CHs (n-propyl, n-pr) or -CH(CH₃)₂ (iso-propyl, i-pr), but is butyl -C₄H₉, -(CH₂)₃CH3, -CHCH3CH2CH3, -CH₂CH(CH₃)₂ or -C(CH₃)₃.

The term substituted alkyl in its broadest sense refers to an alkyl as defined above in the broadest sense, which is covalently linked to an atom that is not carbon or hydrogen, particularly to an atom selected from N, O, F, B, Si, P, S, Cl, Br and I, which itself may be -if applicable- linked to one or several other atoms of this group, or to hydrogen, or to an unsaturated or saturated hydrocarbon (alkyl or aryl in their broadest sense). In a narrower sense, substituted alkyl refers to an alkyl as defined above in the broadest sense that is substituted in one or several carbon atoms by groups selected from amine NH2, alkylamine NHR, imide NH, alkylimide NR, amino(carboxyalkyl) NHCOR or NRCOR, hydroxyl OH, oxyalkyl OR, oxy(carboxyalkyl) OCOR, carbonyl O and its ketal or acetal (OR)₂, nitril CN, isonitril NC, cyanate CNO, isocyanate NCO, thiocyanate CNS, isothiocyanate NCS, fluoride F, choride Cl, bromide Br, iodide I, phosphonate PO3H2, POsR₂, phosphate OPO3H2 and OPOsR₂, sulfhydryl SH, suflalkyl SR, sulfoxide SOR, sulfonyl SO₂R, sulfanylamide SO₂NHR, sulfate SO₃H and sulfate ester SO₃R, wherein the R substituent as used in the current paragraph, different from other uses assigned to R in the body of the specification, is itself an unsubstituted or substituted Ci to C12 alkyl in its broadest sense, and in a narrower sense, R is methyl, ethyl or propyl unless otherwise specified.

The term amino-substituted alkyl or hydroxyl substituted alkyl refers to an alkyl according to the above definition that is modified by one or several amine or hydroxyl groups NH2, NHR, NR2 or OH, wherein the R substituent as used in the current paragraph, different from other uses assigned to R in the body of the specification, is itself an unsubstituted or substituted Ci to C12 alkyl in its broadest sense, and in a narrower sense, R is methyl, ethyl or propyl unless otherwise specified. An alkyl having more than one carbon may comprise more than one amine or hydroxyl. Unless otherwise specified, the term “substituted alkyl” refers to alkyl in which each C is only substituted by at most one amine or hydroxyl group, in addition to bonds to the alkyl chain, terminal methyl, or hydrogen.

Non-limiting examples of amino-substituted alkyl include -CH2NH2, -CH2NHMe, -CH2NHEt,

-CH2CH2NH2, -CH₂CH₂NHMe, -CH₂CH₂NHEt, -(CH₂)₃NH2, -(CH₂)₃NHMe, -(CH₂)₃NHEt,

-CH₂CH(NH₂)CH₃, -CH₂CH(NHMe)CH₃, -CH₂CH(NHEt)CH₃, -(CH₂)₃CH₂NH₂,

-(CH₂)₃CH₂NHMe, -(CH₂)₃CH₂NHEt, -CH(CH₂NH₂)CH₂CH₃, -CH(CH₂NHMe)CH₂CH₃,

-CH(CH₂NHEt)CH₂CH₃, -CH₂CH(CH₂NH₂)CH₃, -CH₂CH(CH₂NHMe)CH₃,

-CH₂CH(CH₂NHEt)CH₃, -CH(NH₂)(CH₂)₂NH₂, -CH(NHMe)(CH₂)₂NHMe,

-CH(NHEt)(CH₂)₂NHEt, -CH₂CH(NH2)CH₂NH2, -CH₂CH(NHMe)CH₂NHMe,

-CH₂CH(NHEt)CH₂NHEt, -CH₂CH(NH2)(CH₂)₂NH2, -CH₂CH(NHMe)(CH₂)₂NHMe,

-CH₂CH(NHEt)(CH₂)₂NHEt, -CH₂CH(CH₂NH₂)₂, -CH₂CH(CH₂NHMe)₂ and

-CH₂CH(CH₂NHEt)₂ for terminal moieties and -CH2CHNH2-, -CH₂CHNHMe-, -CH₂CHNHEt- for an amino substituted alkyl moiety bridging two other moieties.

The term carboxyl-substituted alkyl refers to an alkyl according to the above definition that is modified by one or several carboxyl groups COOH, or derivatives thereof, particularly carboxylamides CONH2, CONHR and CONR2, or carboxylic esters COOR, with R having the meaning as laid out in the preceding paragraph and different from other meanings assigned to R in the body of this specification.

The term halogen-substituted alkyl refers to an alkyl according to the above definition that is modified by one or several halogen atoms selected (independently) from F, Cl, Br, I.

The term aryl in the context of the present specification relates to a cyclic aromatic C5-C10 hydrocarbon that may comprise a heteroatom (e.g. N, O, S). Examples of aryl include, without being restricted to, phenyl and naphthyl, and any heteroaryl. A heteroaryl is an aryl that comprises one or several nitrogen, oxygen and/or sulphur atoms. Examples for heteroaryl include, without being restricted to, pyrrole, thiophene, furan, imidazole, pyrazole, thiazole, oxazole, pyridine, pyrimidine, thiazin, quinoline, benzofuran and indole. An aryl or a heteroaryl in the context of the specification additionally may be substituted by one or more alkyl groups.

An alkylaryl in the context of the present specification relates to an alkyl group substituted by an aryl moiety. Particular examples are ethylphenyl, propylphenyl, butylphenyl and their higher homologues. A substituted alkylaryl may be substituted by the substituent indicated on the alkyl part, if chemically feasible, or on the aryl part of the moiety.

A carboxylic ester is a group -CO2R, with R being defined further in the description. A carboxylic amide is a group -CONHR, with R being defined further in the description.

A polymer of a given group of repeat units is a homopolymer (made up of a multiple of the same repeat unit); a copolymer of a given selection of repeat units is a heteropolymer constituted by repeat units of at least two of the group.

A block copolymer is defined as a polymer in which there is an arrangement of blocks (particularly a linear arrangement of blocks), a block being defined as a portion of the polymer molecule in which the repeat unitic units have at least one constitutional or configurational feature absent from the adjacent portions. In a block copolymer, the distinguishing feature is constitutional, i.e. each of the blocks comprises units derived from a characteristic species of repeat unit.

Detailed Description of the Invention

A first aspect of the invention relates to a block polymer compound comprising, or essentially consisting of, a. an oleophilic block comprising or essentially consisting of a polymer of first repeat units comprising linear, branched and/or cyclic Ce-24 alkyl side chains, and b. a surface-anchoring block comprising or essentially consisting of second repeat units bearing side chains conducive to the attachment to a solid surface,

The oleophilic block and the first repeat units

In general, the oleophilic block can be described as a polymer of first repeat units comprising or essentially consisting of alkyl side chains having 6 or more carbon atoms.

In a particular embodiment, the oleophilic block is a polymer of first repeat units comprising or essentially consisting of alkyl side chains having, per average over the entire number of repeat units comprised in the oleophilic block, 10 or more carbon atoms. In a more particular embodiment, the oleophilic block is a polymer of first repeat units comprising or essentially consisting of alkyl side chains having, per average, 14 or more carbon atoms.

In an even more particular embodiment, the oleophilic block comprises, or essentially consists of, first repeat units comprises alkyl chains having Ce-24 alkyl side chains, and the average chain length of the alkyl chains is 10 or more, more particularly 14 or more carbon atoms.

In certain embodiments, the first repeat units are all the same. These embodiments are documented in the examples disclosed herein and are easily obtained at low scale in the experimental laboratory, allowing analysis of the chain length’s and composition’s influence on polymer behaviour.

In an industrial setting, a mix of Ce-24 alkyl side chains is likely to be more relevant, as it is more economically obtainable. The inventors know from experience, and some basis exists in the literature (Muraki et al. Proc. Inst. Meeh. Eng. Part J J. Eng. Tribol. 224, 55-63 (2010)), that a small proportion of C24 (very un-polar) alkyl side chains can solubilize a larger molar proportion of shorter (e.g. Ci or C2) side chains, demonstrating that a balance can exist between longer and shorter chains, as long as the general principle is adhered to that the bulk of the oleophilic block solubilizes the oleophilic part of the copolymer in non-polar base oils.

In certain embodiments, the repeat units in the oleophilic block are not all substituted with a long alkyl group. A small percentage of repeat units, <30%, particularly <20% and even more particularly <10% of repeat units bear a short chain (Ci to C4 alkyl, particularly C1-C2 alkyl) unsubstituted.

The inventors succeeded in preparing a block polymer in which the oleophilic block was comprised of 50% to 30% of unmodified methacrylic acid methyl ester, and the remaining 50% to 70% repeat units were a mix of longer chain (C12-C24) acyl esters.

In certain embodiments, the first repeat units comprise methacrylate Ce-24 alkyl esters.

In certain embodiments, the first repeat units comprise acrylate Ce-24 alkyl esters.

The bottle-brush nature of dodecyl methacrylate polymer makes it very soluble in most oils. The methacrylate part is quite polar, so it needs a good amount of methylene groups in the alkyl chains to compensate. The inventors predict that shorter chains will improve solubility in more polar, synthetic or natural oils.

In certain embodiments, the oleophilic block is constituted of first repeat units bearing linear alkyl chains. In certain embodiments, the oleophilic block is constituted of first repeat units bearing linear and branched alkyl chains. In certain embodiments, the oleophilic block is constituted of first repeat units bearing only linear alkyl chains. In certain embodiments, the oleophilic block is constituted of first repeat units bearing cyclic alkyl chains. In certain embodiments, the oleophilic block is constituted of first repeat units bearing linear and cyclic alkyl chains.

The surface-anchoring block and the second repeat units

In general, any second repeat unit can be employed that has surface-anchoring properties and is compatible with the base oil.

In general, the surface-anchoring block comprises second repeat units bearing side chains comprising one or several moieties selected from:

- amino (NH₂, -NHR^N, -NR^N ₂, -N⁺R^N ₃), particularly N(CH₃)₂;

- carboxyl (-COOH), U-keto-carboxyl (-COCH₂COOH)), amide (-CONH₂, -CONR^N ₂) or hydroxamate (-CON(R^N)OH)

- aliphatic or aromatic hydroxy (-OH), particularly a catechol or gallol (1 ,2,3- trihydroxybenzene), a dopamine, a nitrodopamine, mimosine, or an anacheline;

- a phosphate or a phosphonate alkyl ester (-PO₃R^p ₂), particularly -PO₃(Et)₂,

- thiol or thioalkylether (-SH or -SR^T), particularly poly (propylene sulfide);

- alkylsilylether (-O-SiR^Sl ₃) or a chlorosilane;

- an n-heterocyclic carbene, a perfluorophenyl azide, a benzophenone, a diaryldiazomethane, or an organoboron; wherein each R^N, R^p, R^T, R^S| is individually selected from unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein each R^N, R^p, R^T, R^S| is individually selected from unsubstituted C1-C4 alkyl.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several amino moieties (NH₂, -NHR^N, -NR^N ₂, -N⁺R^N ₃), particularly N(CH₃)₂, wherein each R^N is unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein R^N is unsubstituted C1-C4 alkyl.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several carboxyl (-COOH) moieties.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several R>-keto-carboxyl (-COCH₂COOH)) moieties.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several amide moieties (-CONH₂, -CONR^N ₂), wherein each R^N is unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein R^N is unsubstituted Ci- C4 alkyl.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several hydroxamate moieties (-CON(R^N)OH), wherein each R^N is unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein R^N is unsubstituted Ci- 04 alkyl.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several aliphatic or aromatic hydroxy (-OH) moieties. In certain particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing a catechol moiety. In certain particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing a gallol moiety. In certain particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing a dopamine moiety. In certain particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing a mimosine moiety. In certain particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing an anacheline moiety.

In certain very particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing a nitrodopamine moiety. Nitrodopamine has been found to offer particularly advantageous properties when the objective is attachment to steel or titanium surfaces.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several (particularly: one) phosphate or phosphonate alkyl ester (- PO₃R^P ₂) moieties, wherein each R^p is unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein R^p is unsubstituted C1-C4 alkyl. In certain particular embodiments, the second repeat units comprise or essentially consist of repeat units bearing a phosphate ethyl ester -POs(Et)2 moiety. Phosphate ethyl ester has been found to offer particularly advantageous properties when the objective is attachment to steel or aluminium surfaces.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several thiol or thioalkylether (-SH or -SR^T) moieties, wherein each R^T is unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein R^T is unsubstituted Ci- 04 alkyl. Thiols or thioalkylethers have been found to offer particularly advantageous properties when the objective is attachment to coinage metal surfaces.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing one or several alkylsilylether (-O-SiR^Sls) moieties, wherein each R^S| is unsubstituted or OH-substituted alkyl Ci-Ce alkyl, particularly wherein R^S| is unsubstituted Ci- C4 alkyl. Chlorosilane has been found to offer particularly advantageous properties when the objective is attachment to silica or ceramic surfaces.

In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing an n-heterocyclic carbene. In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing a perfluorophenyl azide. In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing a benzophenone. In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing a diaryldiazomethane. In certain embodiments, the second repeat units comprise or essentially consist of repeat units bearing an organoboron. Pentafluorophenyl azide has been found to offer particularly advantageous properties when the objective is attachment to organic surfaces.

In certain embodiments, the second repeat units comprise or consist of methacryl(alkylamide) or acryl(alkylamide) units of formula -CH2-CR^A(CONHR^S)-, in which R^A is H or CH3 and R^s is an alkyl bearing a surface-anchoring moiety, particularly a surfaceanchoring moiety as described above.

In certain embodiments, the second repeat units comprise or consist of methacryl(alkylester) or acryl(alkylester) units of formula -CH2-CR^A(CO2R^S)-, in which R^A is H or CH3 and R^s is an alkyl bearing a surface-anchoring moiety, particularly a surface-anchoring moiety as described above.

In certain particular embodiments of the block copolymer compound according to the invention, wherein the second repeat units are -CH2-CR^A(CONHR^S)- or -CH2-CR^A(CO2R^S)-, R^A is H and R^s is an alkyl bearing a surface-anchoring moiety selected from alkyl, alkylene or alkylaryl substituted with one or more amino, carboxyl, hydroxyl, amide, phosphonate alkyl ester, thiol, thioalkylether, or alkylsilylether.

In certain particular embodiments of the block copolymer compound according to the invention, wherein the second repeat units are -CH2-CR^A(CONHR^S)- or -CH2-CR^A(CO2R^S)-, R^A is methyl and R^s is an alkyl bearing a surface-anchoring moiety selected from alkyl, alkylene or alkyl substituted with one or more amino, carboxyl, hydroxyl, amide, phosphonate alkyl ester, thiol, thioalkylether, or alkylsilylether.

In certain particular embodiments, the second repeat units comprise or consist of methacryl(alkylamide) units of formula -CH2-C(CH3)(CONHR^S)-, in which R^s is an alkyl bearing a surface-anchoring moiety, particularly a surface-anchoring moiety as described above. In certain particular embodiments, the second repeat units comprise or consist of methacryl(alkylester) units of formula -CH2-C(CH3)(COOR^S)-, in which R^s is an alkyl bearing a surface-anchoring moiety, particularly a surface-anchoring moiety as described above.

In certain particular embodiments thereof, R^s is an alkyl bearing a surface-anchoring moiety selected from alkyl, alkylene or alkylaryl substituted with one or more amino, carboxyl, hydroxyl, amide, phosphonate alkyl ester, thiol, thioalkylether, or alkylsilylether.

Catechols have been found to show particularly advantageous properties in applications where attachment to metal, particularly steel, surfaces is the objective. The best group for anchoring the block copolymer to steel surfaces in the hands of the inventors has proven to be nitrodopamine.

In certain particular embodiments, the second repeat units are selected from the following groups: a. Acrylate N-(alkylcatechyl) amides or methacrylate N-(alkylcatechyl) amides. In a particular embodiments, the second repeat units are N-(nitrodopamine) amides. Therein, the carboxyl group of the polymerized acryl or methacryl moiety is coupled to the aliphatic nitrogen on the nitrodopamine. b. Acrylate I methacrylate a>-carboxylalkyl amides or a>-carboxylalkyl esters. Therein, the carboxyl group of the polymerized acryl or methacryl moiety is coupled to a linear alkyl bearing a hydroxy or amine group on the alkyl C1 by ester or amide bond, respectively. The linked alkyl also bears a carboxyl (COOH) on the last (omega) carbon. c. Acrylate I methacrylate a>-phosphate or a>-phosphonate alkyl esters, or a>-phosphate or a>-phosphonate alkyl amides, particularly a>-PO3(Et)2 alkyl esters or amides. Therein, the carboxyl group of the polymerized acryl or methacryl moiety is coupled to a linear alkyl bearing an hydroxy or amine group on the alkyl C1 by ester or amide bond, respectively. The linked alkyl also bears a phosphate or phosphonate, particularly a POs(Et)2 moiety on the last (omega) carbon. d. Acrylate I methacrylate o-amine alkyl esters, or o-amine alkyl amides, particularly wherein the amine is selected from -NH2, -NHR^N, -NR^N2, -N⁺R^N3, with RN selected from C1-C4 alkyl. Therein, the carboxyl group of the polymerized acryl or methacryl moiety is coupled to a linear alkyl bearing a hydroxy or amine group on the alkyl C1 by ester or amide bond, respectively. The linked alkyl also bears the amine functionality on the last (omega) carbon of the attached alkyl chain.

Block copolymers in which the surface anchoring block consists of repeat units having amines, particularly primary (NH2) amines, or lower (Ci to C3) alkyl secondary and tertiary amines, as anchoring moiety, have been found by the inventors to reduce wear (see examples). e. Acrylate I methacrylate co -thiol (SH) or co-thioalkylether (-SR^T), wherein R^T is unsubstituted C1-C4 alkyl; the designation c -thiol (SH) or co-thioalkylether follows the same rationale as the groups previously mentioned under a to d hereunder. f. Acrylate I methacrylate co-alkylsilylether (-O-SiR^Sls) or co-chlorosilane; the designation co-alkylsilylether I co-chlorosilane follows the same rationale as the groups previously mentioned under a to d hereunder. g. Acrylate I methacrylate co-n-heterocyclic carbene, acrylate or methacrylate co- perfluorophenyl azide, acrylate or methacrylate co- benzophenone, acrylate or methacrylate co-diaryldiazomethane, or acrylate or methacrylate co-organoboron.

In certain even more particular embodiments, the second repeat units are acrylate or methacrylate N-(alkylcatechyl) amides, particularly N-(nitrodopamine) amides.

In certain other even more particular embodiments, the second repeat units are acrylate or methacrylate co-carboxylalkyl amides or co-carboxylalkyl esters:

-[CH₂-CR^ACONHR^S]- or -[CH₂-CR^ACOOR^S]- wherein R^A is H or CH₃, and R^s is a C₂ to Ci₂ co-carboxylalkyl, particularly R^s is C_nH_n+2COOH, more particularly R^s is (CH₂)_nCOOH, with n being selected from 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

In certain other even more particular embodiments, the second repeat units are acrylate or methacrylate co-phosphate or co-phosphonate alkyl amides or esters, particularly co-POs(Et)₂: -[CH₂-CR^ACONHR^S]- or -[CH₂-CR^ACOOR^S]- wherein R^A is H or CH₃, and R^s is a C₂ to Ci₂ alkyl-co-phosphate or alkyl-co-phosphonate, particularly R^s is C_nH_n+2OPO3R^P2, or C_nH_n+2PO3R^P2, more particularly R^s is (CH₂)_nOPO3R^P2 or (CH₂)_nPO3R^P2, with R^p being selected from Ci - C4 alkyl, and n being selected from 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

In certain other even more particular embodiments, the second repeat units are acrylate or methacrylate alkyl-co-amine esters, or alkyl-co-amine amides, particularly wherein the amine is selected from -NH₂, -NHR^N, -NR^N ₂, -N⁺R^N3, with RN selected from C¹ to C³ alkyl: -[CH₂-CR^ACONHR^S]- or -[CH₂-CR^ACOOR^S]- wherein R^A is H or CH₃, and R^s is a C₂ to Ci₂ a>-aminolalkyl, particularly R^s is C_nH_n+2NH₂, C_nH_n+2NHR^N, C_nH_n+₂NR^N ₂, or CnH_n+2N⁺R^N3, more particularly R^s is selected from -(CH₂)_nNH₂, -(CH₂)_nNHR^N, - (CH₂)_nNR^N ₂, or -(CH₂)_nN⁺R^N ₃, with R^N being selected from Ci - C4 alkyl, and n being selected from 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

In certain other even more particular embodiments, the second repeat units are acrylate or methacrylate alkyl-a>-thiol (SH) or alkyl-a>-thioether (-SR^T), wherein R^T is C1-C4 alkyl:

-[CH₂-CR^ACONHR^S]- or -[CH₂-CR^ACOOR^S]- wherein R^A is H or CH₃, and R^s is a C₂ to Ci₂ alkyl-a>-thiol or alkyl-a>-thioether, particularly R^s is C_nH_n+2SH, or C_nH_n+2SR^T, more particularly R^s is (CH₂)_nSH or (CH₂)_nSR^T, with R^T being selected from Ci - C4 alkyl, and n being selected from 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

In certain other even more particular embodiments, the second repeat units are acrylate or methacrylate alkyl-o-silylether (-O-SiR^Sls) or alkyl-a>-chlorosilane:

-[CH₂-CR^ACONHR^S]- or -[CH₂-CR^ACOOR^S]- wherein R^A is H or CH₃, and R^s is a C₂ to C12 alkyl-o-silylether, particularly R^s is C_nH_n+₂O-SiR^Sl3, more particularly R^s is (CH₂)_nO- SiR^Si ₃, with R^S| being selected from Ci - C4 alkyl, and n being selected from 1 , 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11.

The make-up of the block copolymer and general architecture

In certain embodiments, an oleophilic block is comprised of between 15 and 400 repeat units.

In certain particular embodiments, an oleophilic block is comprised of between 30 and 300 repeat units. In certain particular embodiments, an oleophilic block is comprised of between 30 and 200 repeat units. In certain particular embodiments, an oleophilic block is comprised of between 30 and 100 repeat units. The inventors have found that decreasing the amount of first repeat units in the oleophilic block from 375 to lower values increased performance of the molecule. Without wishing to be bound by theory, they assume that this observation might be explained by the fact that too large a size of the molecule hinders a close packed arrangement, and hence the polymer is not efficiently anchored.

In certain more particular embodiments, an oleophilic block is comprised of between 40 and 60 repeat units. In certain embodiments, a surface-anchoring block is comprised of between 3 and 300 repeat units. In certain particular embodiments, a surface-anchoring block is comprised of between 20 and 300 repeat units.

In certain more particular embodiments, a surface-anchoring block is comprised of between 30 and 80 repeat units. In certain even more particular embodiments, a surface-anchoring block is comprised of between 30 and 60 repeat units.

One particularly advantageous embodiment had a oleophilic:surface anchoring repeat unit composition of 42:36 repeat units, respectively, with the surface anchoring repeat units having a nitrodopamine moiety.

In certain embodiments, a ratio between the number of repeat units comprised in the oleophilic block and the number of repeat units in the surface-anchoring block ranges between 3:1 and 1 :2, particularly wherein said ratio ranges between 2:1 and 1 :1 , more particularly wherein said ratio is 7:6.

In certain particular embodiments, the oleophilic block consists of 42 repeat units and the surface-anchoring block consists of 36 nitrodopamine repeat units.

In certain particular embodiments, the copolymer is a linear copolymer.

In certain particular embodiments, the copolymer is composed of two blocks, one oleophilic and one surface-anchoring.

In certain embodiments, the copolymer is a linear copolymer that comprises two oleophilic blocks flanking a surface-anchoring block.

In certain particular embodiments, the copolymer is a linear copolymer consisting of one oleophilic block and one surface-anchoring block.

In certain embodiments, the block polymer is the product of radical polymerization. In certain particular embodiments, the block polymer is synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization.

In certain particular embodiments, the block polymer is synthesized by atom-transfer radical polymerization (ATRP).

A further aspect of the invention relates to the use of a copolymer compound as described herein in any of the aspects or embodiments recited herein, as a friction-reducing additive in a lubricating composition. Such lubricating composition in particular embodiments comprises mineral oil, and optionally any of the further additives known in the art to be useful to adapting a lubricating composition to its particular use. In certain particular embodiments, the lubricating composition only contains mineral oil and the lubricant copolymer compound according to the invention. In certain embodiments, the lubricating composition comprises or essentially consists of synthetic oil. The American Petroleum Institute (API) has categorized base oils into five categories (API 1509, Appendix E). The first three groups are refined from petroleum crude oil. Group IV base oils are full synthetic (polyalphaolefin, PAO) oils. Group V is for all other base oils not included in Groups I through IV.

As used herein, the term “synthetic oils” is synonymous with PAO.

In certain embodiments, the lubricating composition comprises or essentially consists of natural oil. The term “natural oil” as used herein refers to base oils derived from plants mostly. Ester oils fall partially in this category as the tested EO6 (high-oleic sunflower oil).

In certain embodiments, the lubricating composition is applied to lubricate steel components.

A further aspect of the invention relates to a lubricant composition containing a copolymer compound as described herein in any of the aspects or embodiments recited herein, and nonpolar base oil.

In certain embodiments, the base oil is a non-polar base oil, i.e. a base oil constituted of saturated hydrocarbon compounds or naphthenic oils. Naphthenic oils are rich in cycloalkanes.

In certain alternative embodiments, the base oil is a polar base oil, particularly an ester oil. One example of a synthetic ester oil is ethyl-hexyl-oleate.

In certain embodiments, the lubricant composition is characterized by a concentration of the copolymer lubricant compound according to the invention, relative to the base oil, of 5%-0.05% (w/w), particularly 1 % to 0.1 %.

In certain particular embodiments of the lubricant composition according to the invention, the concentration of the copolymer lubricant compound relative to the base oil is 1 % to 0.1 %., and the lubricant copolymer is characterized by methacrylate alkyl esters having an average chain length of the alkyl chains of >6 carbon atoms, particularly >10 carbon atoms, more particularly >12 carbon atoms; the base oil is a non-polar base oil, particularly a polyalphaolefin.

In certain embodiments, the surface-anchoring block comprises of more than one type of second repeat units. Attaching different anchors to the same polymer is useful in systems with more than one material present. One example is a machine that comprises moving parts with more than one metal, or both metal and ceramic or polymer surfaces, or has areas of the metal that are coated with oxide or other additive reaction products. In such applications, multichemistry binding is useful.

The additive according to the invention is of particular advantage in settings where relatively low speeds of components are expected. In contrast, the polymer friction modifiers known in the art are relatively ineffective in low-speed conditions since they are not strong enough to maintain separation of surfaces under shearing forces of opposing sliding surfaces. The prior art additives show film thicknesses of below 10 nm at the slowest speeds, whereas those determined by the inventors for exemplary additives according to the invention, are 20-30 nm in thickness. Thicker films are of advantage, both in terms of friction and wear protection.

The invention in certain aspects and embodiments relates to a compound that comprises a diblock copolymer, in which one block presumably serves to form polymer brushes on the steel while the other serves to anchor the chain to the steel surface via multiple surface-reactive groups. Alternatively, the invention provides O-S-O triblock copolymers (O designating the oleophilic block, S the surface-anchoring block).

Polymer brushes consist of a carpet made of end-grafted polymer chains, which, when in the presence of a good solvent, stretch out into it to maximize their solvation. In this case the solvent is the lubricating oil. The examples of the present invention use long chain alkyl acrylate as the first application envisions their use as an additive in a petroleum-fraction oil, but one could use any appropriate repeat unit to maximize solubility in the oil. One non-limiting example is the use of shorter hydrocarbon chains in the oleophilic first repeat units to increase solubility in an ester oil, which is more polar.

Polymer brushes are known to exhibit low friction, in general, but in the presence of high loads and shear forces, the individual polymer chains can be ripped off the surface. This renders necessary a highly effective surface-anchoring mechanism. In the present invention, the anchoring mechanism comprises an entire block of surface-binding groups, thus ensuring firm attachment of the brush-forming chain to the surface. In a preferred embodiment, a 12kDa block of poly(dodecyl methacrylate) (p(12MA), the brush former) is attached to a 9 kDa block of poly(pentafluorophenyl acrylate) (pPFPA). The PFPA units in the second block can readily be substituted by a variety of appropriate surface-anchoring groups. The synthesis of the polymeric friction modifiers was done in three steps: first an oleophilic polymer was grown with an active chain end. Secondly the reactive functional block was added. And in the third step the functional moieties were replaced with the anchoring units.

In a particularly successful embodiment, the anchoring groups consisted of nitrodopamine, which is known to attach to transition metal and oxide surfaces by covalent and coordinative bonding. At a concentration of 0.5 wt% in the model base oil, hexadecane (HD), the additive substantially reduces friction, in rolling/sliding contact (50% sliding) compared to the base oil. At slow speeds, the friction coefficient for pure HD under a load of 2N (0.38 GPa maximum pressure) is around 0.3. In the presence of the additive, this is reduced 6-fold to 0.05. Glycerol mono-oleate, a commercially used friction modifier, at the same weight loading, leads to a 3- fold higher friction coefficient than the invention. The binding strength to the surface is even maintained under pure sliding and 36 N load (1 GPa pressure), and even at these extreme conditions, a friction coefficient of 0.1 is recorded.

The invention further encompasses the following items:

Item 1. A block polymer compound comprising, or essentially consisting of, a. an oleophilic block comprising of first repeat units comprising Ce-24 alkyl side chains, and b. a surface-anchoring block comprising second repeat units bearing side chains conducive to the attachment on a solid surface.

Item 2. The block polymer according to item 1 , wherein the oleophilic block consists of first repeat units comprising Ce-24 alkyl side chains.

Item 3. The block polymer according to item 1 or 2, wherein the first repeat units comprise alkyl chains having more than ten carbon atoms, particularly wherein the first repeat units comprise Ce-24 alkyl side chains, more particularly wherein the first repeat units are seleceted from methacrylate Ce-24 alkyl esters and acrylate Ce-24 alkyl esters.

Item 4. The block polymer according to any one of the preceding items 1 to 3, wherein the surface-anchoring block consists of second repeat units bearing side chains conducive to the attachment on a solid surface.

Item 5. The block polymer according to any one of the preceding items 1 to 4, wherein the surface-anchoring block comprises second repeat units bearing side chains comprising one or several moieties selected from: i. amino (NH₂, -NHR^N, -NR^N ₂, -N⁺R^N ₃), particularly N(CH₃)₂; ii. carboxyl (-COOH), G-keto-carboxyl (-COCH₂COOH)), amide (-CONH₂, -CONR^N ₂) or hydroxamate (-CON(R^N)OH); ill. aliphatic or aromatic hydroxy (-OH), particularly a catechol or gallol, a dopamine, a nitrodopamine, mimosine, or an anacheline; iv. a phosphate or a phosphonate alkyl ester (-PO₃R^p ₂), particularly -PO₃(Et)₂, v. thiol or thioalkylether (-SH or -SR^T), particularly poly (propylene sulfide); vi. alkylsilylether (-O-SiR^Sl ₃) or a chlorosilane; vii. an n-heterocyclic carbene, a perfluorophenyl azide, a benzophenone, a diaryldiazomethane, or an organoboron; wherein each R^N, R^p, R^T, R^S| is individually selected from unsubstituted or OH- substituted alkyl Ci-Ce alkyl, particularly wherein each R^N, R^p, R^T, R^S| is individually selected from unsubstituted C1-C4 alkyl.

Item 6. The block polymer according to any one of the preceding items 1 to 5, wherein the surface-anchoring block comprises second repeat units bearing amine side chains.

Item 7. The block polymer according to any one of the preceding items 1 to 6, wherein the second repeat units comprise amine moieties, characterized in that the amines are selected from primary amines (NH2), secondary alkyl amines (-NHR^N), tertiary alkyl amines -NR^N2, -N⁺R^N ₃), with R^N being selected from unsubstituted or OH-substituted, particularly unsubstituted, C1-C4 alkyl.

Item 8. The block polymer according to any one of the preceding items 1 to 7, wherein the second repeat units comprise amine moieties selected from NH2, NH(CH₃), N(CH₃)2, -N⁺(CH₃)₃, particularly wherein the second repeat units comprise amine moieties selected from NH₂, NH(CH₃), N(CH₃)₂.

Item 9. The block polymer according to item 8, wherein the second repeat moieties are selected from hexylamine and hexyl(dimethyl)amine.

Item 10. The block polymer according to any one of the preceding items 1 to 9, wherein the surface-anchoring block comprises as second repeat units methacryl(alkylamide) or acryl(alkylamide) units of formula -CH2-CR^A(CONHR^S)-, in which R^A is H or methyl and R^s is an alkyl bearing a surface-anchoring moiety, particularly a surface-anchoring moiety selected from alkyl, alkylene or alkylaryl substituted with one or more amino, carboxyl, hydroxyl, amide, phosphonate alkyl ester, thiol, thioalkylether, or alkylsilylether.

Item 11 . The block copolymer according to any one of the preceding items 1 to 10, wherein the second repeat units are selected from a. acrylate or methacrylate N-(alkylcatechyl) amides, particularly N-(nitrodopamine) amides, b. acrylate or methacrylate alkyl-a>-carboxyl amides or alkyl-a>-carboxyl esters, c. acrylate or methacrylate alkyl-a>-phosphate or alkyl-a>-phosphonate esters, particularly o-P0₃(Et)2, d. acrylate or methacrylate o-amine alkyl esters, or o-amine alkyl amides, particularly wherein the amine is selected from -NH2, -NHR^N, -NR^N2, -N⁺R^N ₃, with RN selected from C1-C4 alkyl; more particularly selected from C6H12NH2 and CeHi2N(CH₃)2; e. acrylate or methacrylate alkyl-o-th lol (SH) or al kyl-co-th ioether (-SR^T), wherein R^T is C1-C4 alkyl; f. acrylate or methacrylate o-alkylsilylether (-O-SiR^Sls) or a>-chlorosilane; g. acrylate or methacrylate a>-n-heterocyclic carbene, acrylate or methacrylate 0- perfluorophenyl azide, acrylate or methacrylate 0- benzophenone, acrylate or methacrylate a>-diaryldiazomethane, or acrylate or methacrylate a>-organoboron. particularly wherein the second repeat units are acrylate or methacrylate N- (alkylcatechyl) amides, particularly N-(nitrodopamine) amides.

Item 12. The block polymer according to any one of the preceding items, wherein an oleophilic block is comprised of between 15 and 400 repeat units, particularly wherein an oleophilic block is comprised of between 30 and 100 repeat units, more particularly wherein an oleophilic block is comprised of between 40 and 60 repeat units.

Item 13. The block polymer according to any one of the preceding items, wherein a surface-anchoring block is comprised of between 3 and 300 repeat units, particularly between 20 and 300 repeat units, more particularly wherein a surface-anchoring block is comprised of between 30 and 80 repeat units, more particularly wherein a surfaceanchoring block is comprised of between 30 and 60 repeat units.

Item 14. The block polymer according to any one of the preceding items, wherein a ratio between the number of repeat units comprised in the oleophilic block and the number of repeat units in the surface-anchoring block ranges between 3:1 and 1 :2, particularly wherein said ratio ranges between 2:1 and 1 :1 , more particularly wherein said ratio is 7:6.

Item 15. The block polymer according to any one of the preceding items, wherein the oleophilic block consists of 42 repeat units and the surface-anchoring block consists of 36 nitrodopamine repeat units.

Item 16. The block polymer according to any one of the preceding items, wherein the block polymer is the product of radical polymerization, particularly wherein the block polymer is synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization.

Item 17. The block polymer according to any one of the preceding items, wherein the block polymer is synthesized by atom-transfer radical polymerization (ATRP).

Item 18. The block polymer according to any one of the preceding items, consisting of one or several oleophilic blocks, and one or several surface-anchoring blocks. Item 19. The block polymer according to any one of the preceding items, consisting of one oleophilic block, and one surface-anchoring block.

Item 20. Use of a block polymer compound according to any one of the preceding items as a friction-reducing additive in a lubricating composition.

Item 21 . Use of a block polymer compound according to any one of the preceding items as a wear-reducing additive in a lubricating composition, particularly wherein the additive is described by any one of items 6 to items 9.

Item 22. The use according to item 21 , wherein the lubricating composition comprises synthetic oil, particularly a synthetic polyalphaolefin.

Item 23. The use according to item 20 to 22, wherein the lubricating composition consists of synthetic oil, particularly of a synthetic polyalphaolefin.

Item 24. The use according to item 20 to 23, wherein the lubricating composition comprises mineral oil or natural oil.

Item 25. A lubricant composition containing a block polymer compound according to any one of the preceding items 1 to 19, and non-polar base oil.

Item 26. The lubricant composition according to item 25, wherein the concentration of the compound relative to the base is 5%-0.05% (w/w), particularly 1 % to 0.05, even more particularly 1 % to 0,1 %.

The invention is further illustrated by the following examples and figures, from which further embodiments and advantages can be drawn. These examples are meant to illustrate the invention but not to limit its scope.

Description of the Figures

Fig. 1 shows (a): aliquot H-NMR measurements during 12MA polymerization, (i) before initiation, (ii) After 21 h at 70 °C. Conversion was determined from the integral ratios of (a1+a2) versus (b+b*); (b): Aliquot ¹⁹F-NMR measurements during PFPA polymerization after a polymerization time of 23 hours.

Fig. 2 shows (a) the impact of architecture on the coefficient of traction of the lubricant additive solutions in hexadecane, using nitrodopamine as a functional group, with comparison to the non-additivated base oil hexadecane, and the commercial additive, glycerol monooleate (GMO) in hexadecane;

(b) the impact of functional group on the coefficient of traction of the lubricant additive solutions in hexadecane, using architecture B from Example 1 (oleophilic, functional DPs of 42 and 36, respectively), with comparisons to the non-additivated base oil hexadecane, and the commercial additive, glycerol monooleate (GMO) in hexadecane.

Fig. 3 compares the coefficient of traction of the lubricant additive B1 (using nitrodopamine as a functional group) in (a) polyalpha olefins (PAO)2 and (b) PAO6 with the non-additivated base oil, and glycerol monooleate (GMO).

Fig. 4 shows the result of a high-frequency reciprocating rig (HFRR) wear test using four block polymers according to the invention as additives.

Examples

Example 1: Synthesis

The exemplary synthesis of the polymeric friction modifiers can be differentiated into three steps: 1 ) an oleophilic polymer is grown with an active chain end. 2) The reactive functional block is added. 3) The functional moieties are replaced with the anchoring units.

The resulting polymer is a diblock-copolymer with one oleophilic and one surface-adhesive part. This approach allows the effects of polymer structure to be separated, i.e. polymer overall molecular weight as well as the relative sizes of the individual blocks, from the influences of anchoring chemistry. Additionally, the resulting polymer can be characterized well in its intermediate form, whereas for the final, highly amphiphilic polymer GPC and NMR have severe limitations due to solubility and micellization.

The examples shown herein use a RAFT (Reversible addition-fragmentation chain-transfer polymerization) synthesis. The skilled person understands that a ATRP (Atom transfer radical polymerization) might be similarly employed.

Materials

Common solvents and reagents were purchased from commercial suppliers (VWR, Acros, Sigma-Aldrich) at >99% quality and used as received. THF and DMF were dried in-house to <5ppm H2O). Lauryl methacrylate (96%, Acros Organics) was filtered through a basic alumina column to remove inhibitor before use.

Azobisisobutyronitrile (AIBN) (98%, Aldrich) was recrystallized from EtOH before use.

Triethylamine (TEA), (Sigma-Aldrich) was distilled from KOH before use Step 1: Oleophilic Block

Scheme for the first synthetic step.

Two versions of the oleophilic block were synthesized; the numbers in parentheses refer to the lower-molecular-weight version. The CTA/initiator ratio was kept constant at 20/1 . In a 100 ml Schlenk flask a magnetic stirrer was loaded as well as 31 .6 g (30.0 g) lauryl methacrylate, 86.6 mg (820 mg) 2-cyano-2-propyl dodecyl trithiocarbonate, 2 mg (20 mg) mg AIBN, and 31 ml (35 ml) toluene. The flask was closed with a rubber septum and subsequently degassed with five freeze-pump-thaw cycles (liquid nitrogen and pressure < 1e-2 mbar), backfilled with nitrogen, and the polymerization started by immersing the flask into an oil bath at 70 °C.

The conversion of the polymerization was measured by taking aliquots (0.1 ml of solution with 0.4 ml CDCh) for NMR analysis. The resulting conversion was calculated by comparing the olefinic proton intensity to the intensity of the CH2 group adjacent to the ester unit (internal reference). After 21 (12) hours the conversion was at 74 % (80 %) and did not progress any further. Assuming controlled and linear growth, this corresponds to a degree of polymerization of 375 (42) repeat units. The product was purified by precipitation in MeOH, redissolution in hexane and reprecipitation in EtOH. It was dried under high vacuum for at least 18 hours, and analyzed with 1 H-, 19F- and 13C-NMR, as well as ATR-FTIR and THF- GPC.

Step 2: Functional Block a) Repeat unit Synthesis

The pentafluorophenol-acrylate repeat unit was synthesized as described earlier [US20170291971 A1 , incorporated herein by reference]. 15.51 g pentafluorophenol was added to a 250 ml round-bottom flask outfitted with a dropping funnel. The assembly was purged with N2 for 30 min, and sealed with a rubber septum and an Ar balloon was added. 60 ml dry DCM and 9.5 ml lutidine were added with a syringe, and the solution cooled to 0°C in an ice bath. 6.6 ml acryloyl chloride were added dropwise under stirring. The mixture was left to reach room temperature under stirring overnight.

The product mixture was then filtered, extracted with ultrapure water three times, dried with MgSC , one grain of the inhibitor added, and the DCM evaporated at 500 mbar and 40 °C. The product was further purified through distillation at 9 mbar and 61 °C to give a colourless liquid (17.08 g, 88 %). Another grain of inhibitor was added and stored at 4 °C. b) Polymerization

Scheme of the second synthetic step.

Five versions of the block copolymer were synthesized using the two versions of the macro- CTA from step 1 , the repeat unit from step 2a - filtered through neutral alumina - and AIBN as an initiator with toluene as a solvent (20 ml each). The respective weights are tabulated below.

All components were loaded into a 100 ml Schlenk flask that was sealed with a rubber septum. The flask was degassed through 5 repeat freeze-pump-thaw cycles and backfilled with nitrogen, and the polymerization started by immersing the flask into an oil bath at 80 °C. The conversion of the polymerization reaction was quantified by monitoring the ¹⁹F-NMR spectra of aliquots. Here the sharp triplet of the para-F at -157.9 ppm of the repeat unit is clearly distinguishable from the broad polymer peak at -156.8 ppm. The crude product was worked up by precipitation in MeOH, dissolution in hexane, and reprecipitation in EtOH. The polymers were then dried overnight under high vacuum, and analyzed with 1 H-, 19F- and 13C-NMR, as well as ATR-FTIR and THF-GPC.

Step 3: Post-Polymerization Functionalization

Scheme of the third synthetic step. a) Nitrodopamine (polymers A1 , B1 , C1 ...)

Nitrodopamine was synthesized as reported earlier [US20170291971A1], Briefly 5 g of dopamine and 6.3 g of NaNO? were dissolved in 150 ml u. water and cooled to 0°C under stirring in an ice bath. 25 ml sulfuric acid (20 vol%) was added dropwise and the reaction mixture was left stirring and warming up to room temperature overnight. The product mixture was cooled to 0°C again, filtered off, washed with copious amounts of ultrapure water. The resulting nitrodopamine hydrogen sulfate was dried under high vacuum overnight to yield 4.46 g (57 %).

The polymer post-modification was performed for each different polymer from step 2. Per 1 g - which was added to a 2-neck round bottom flask outfitted with a Vigreux column, the flask sealed with a rubber septum, dried under high vacuum for 1 hour, and 10 ml dry THF added under N2.

A 1.1 molar equivalent amount of nitrodopamine - compared to the molarity of PFPA moieties — was added to a Schlenk flask, dried under high vacuum for 1 hour and 10 ml dry DMF added. Once the nitrodopamine was dissolved, the solutions were transferred to the 2- neck flask, 3 equivalents of TEA were added, and reaction temperature set to 50 °C overnight. The conversion was measured by taking aliquots, dissolving in toluene-d8 and measuring the 19F-NMR. In all instances the conversion was measured to be quantitative.

The resulting crude product was dried, dissolved in DCM, precipitated in MeOH at 0 °C, the mixture dissolved in 25 ml of DCM and 4 ml acetic acid, stirred for 3 hours, and precipitated in MeOH at 0 °C again. The polymer was dried under high vacuum overnight. b) N-Boc hexanediamine (polymers A2, B2, C2 ...)

2.03 g of the polymer from step 2B were added to a 2-neck, round-bottom flask equipped with a Vigreux column and dried under high vacuum for 3 hours. 40ml dry THF, 0.9 ml N-Boc-1 ,6- diaminohexane and 1 .5 ml dry TEA were added and the reaction temperature set to 50°C. The progress of the hydrolysis was monitored by measuring 19F-NMR of aliquots of the solution with toluene-d8 as a solvent. 17 hours later, the conversion was measured to be 100%.

The resulting crude product was precipitated in MeOH at 0°C, the mixture dissolved in 25 ml of DCM and 4 ml TFA, stirred overnight, and precipitated in acetone at 0°C twice.

The polymer was dried under high vacuum overnight to yield 1.72 g (98 %). c) Carboxylic acid (polymer B3)

To yield a carboxylic acid, the pentafluorophenol-acrylate was deliberately hydrolyzed - a process that is usually unwanted.

2.02 g of the polymer from step 2B was added to a 2-neck round bottom flask equipped with a Vigreux column. 40ml THF (VWR, as received not dry) and 1.5 ml TEA (not dry) was added, the assembly was closed with a rubber septum, and the reaction temperature set to 50 °C. The progress of the hydrolysis was monitored by measuring 19F-NMR of aliquots of the solution with toluene-d8 as a solvent. After 4 days the conversion did not progress further than 51 %, at which point 1 ml of MilliQ water was added. 18 hours later, the conversion was measured to be 100 %.

The resulting crude product was precipitated in MeOH at 0 °C, the mixture dissolved in 25 ml of DCM and 4 ml acetic acid, stirred for 3 hours, and precipitated in MeOH at 0 °C again. The polymer was dried under high vacuum overnight to yield 1 .07 g (77%).

Example 2: Friction in hexadecane

The coefficient of traction of an oil consisting of hexadecane as a base oil (viscosity 3.0 mPa.s at 25° C), and 0.5 wt.% polymeric friction-reducing additive (dissolved in the hexadecane at 80°C overnight with stirring, centrifuged at 4000 rpm before use) was determined at 30° C using a Mini T raction Machine with a steel ball (E = 210 GPa) of 9.525 mm radius and a smooth steel disk (E = 210 GPa). The load applied was 2 N, leading to a maximum Hertzian contact pressure of 384 MPa. A slide-roll ratio of 50% was used, and the speed was varied from 1 - 2000 mm. s'¹. The additives had architectures A-E as described in Example 1. They had different functionalities, 1 corresponding to nitrodopamine, 2 corresponding to -NH2, and 3 corresponding to -COOH. The results are shown in Fig. 2 a and b.

Example 3: Friction in PAO2 and PAO6

The coefficient of traction of an oil consisting of

(a) PAO2 as base oils (viscosity 4.15 mPa.s at 40° C),

(b) PAO6 as base oil (viscosity 24.9 mPa.s at 40° C), with 0.5 wt.% polymeric friction-reducing additive B1 was determined at 30° C using a Mini Traction Machine with a steel ball (E = 210 GPa) of 9.525 mm radius and a smooth steel disk (E = 210 GPa). The load applied was 2 N, leading to a maximum Hertzian contact pressure of 384 MPa. A slide-roll ratio of 50% was used, and the speed was varied from 1 - 2000 mm. s'¹.

The results are shown in Figure 3 a and b.

Methods of Measurement

MTM

The MTM measurements were performed on a MTM2 (PCS Instruments, UK) at Empa Dubendorf with the standard specimen pack as received and sonicated in isooctane. The temperature was set to 30°C and the normal load kept consistently at 2 N if not explicitly mentioned otherwise. For a typical set the predefined settings for “traction step” and “Stribeck step” were used repeatedly. Running-in effects made the first measurement incomparable to the rest of the set, which is why it was omitted. The data presented for the Stribeck type measurements are averages and their 95 % confidence intervals of 4 repetitions of increasing and decreasing steps. The slide-to-roll ratio (SRR), as defined by:

SRR = U_e/U_s was kept at 50% throughout. The entrainment and sliding speeds are given by

Ue = (Uball + Udisk) / 2

Us ^— | Uball ^— Udisk|

For the traction curve settings, the SRR was varied from 0% to 50%, with a constant entrainment speed of 10 mm/s.

Example 4: High-Frequency Reciprocating Rig (HFRR) Wear Test

The high-frequency reciprocating rig (HFRR) is a device originally developed for measuring diesel lubricity, but it can be used for semi-quantitative wear measurements. It involves reciprocating movement between a small steel ball and a steel flat (for materials see below) under constant load for a fixed time. The wear scar on the ball is measured optically and the measurements converted to a wear volume via simple solid geometrical calculations. The results are useful for comparison, however, while the absolute values will deviate from those obtained from wear measurements carried out at constant speeds.

Upper Specimen (Ball)

The upper specimen is specified to grade 28 (ANSI B3.12), ANSI E-52100 steel, with a Rockwell hardness “C” scale (HRC) number of 58-66 (ISO 6508), and a surface finish of less than 0.05 pm Ra. Lower Specimen (Disc)

The lower specimen is specified to AISI E-52100 steel machined from annealed rod, with Vickers hardness “30Hv” scale number of 190-210 (ISO 6507/1 ). It is turned, lapped and polished to a surface finish of less than 0.02 pm Ra. Results for tests performed on PAO4, nitrodopamine-modified block copolymer (designated TG 2-26 (ND)), primary amine-modified block copolymer (designated TG 2-27 (NH2)), tertiary methylamine-modified block copolymer (designated TG 2-28 (NMe2)) and carboxylate modified block copolymer (designated TG 2-29 (COOH)). Additivated oils, containing the designated block copolymers, are compared with the base oil, PAO4. As can be seen, the best wear performance by far is exhibited by the -NH2-functionalized polymer, closely followed by the - NMe2-functionalized polymer. Experiments were carried out for 1800s, at 40 Hz. The total travel per cycle was 4 mm. Ball radius was 3 mm and the load was 4 N.

The architecture of all tested polymers was P12MA(40)-b-pPFPA(23). Thus there were 23 anchor units holding the P12MA brush-forming block onto the surface.

Claims

1 . A block polymer compound comprising, or essentially consisting of, a. an oleophilic block comprising of first repeat units comprising Ce-24 alkyl side chains, and b. a surface-anchoring block comprising second repeat units bearing side chains conducive to the attachment on a solid surface, wherein the second repeat units comprise a moiety selected from the group of aromatic hydroxy (- OH) moieties.

2. The block polymer according to claim 1 , wherein the second repeat units comprise moieties selected from the group comprising a catechol or gallol, a dopamine, a nitrodopamine, mimosine, or an anacheline.

3. The block polymer according to claim 1 or 2, wherein the second repeat units are selected from acrylate N-(alkylcatechyl) amides and methacrylate N-(alkylcatechyl) amides.

4. The block polymer according to any one of the preceding claims, wherein the second repeat units comprise nitrodopamine moieties, particularly N-(nitrodopamine) amides.

5. The block polymer according to any one of the preceding claims, wherein the oleophilic block consists of first repeat units comprising Ce-24 alkyl side chains.

6. The block polymer according to any one of the preceding claims, wherein the first repeat units comprise alkyl chains are selected from methacrylate Ce-24 alkyl esters and acrylate Ce-24 alkyl esters.

7. The block polymer according to any one of the preceding claims, wherein an oleophilic block comprises between 15 and 400 repeat units.

8. The block polymer according to any one of the preceding claims, wherein a surfaceanchoring block comprises between 3 and 300 repeat units.

9. The block polymer according to any one of the preceding claims, wherein a ratio between the number of repeat units comprised in the oleophilic block and the number of repeat units in the surface-anchoring block ranges between 3:1 and 1 :2.

10. The block polymer according to any one of the preceding claims, wherein the oleophilic block consists of 42 repeat units and the surface-anchoring block consists of 36 nitrodopamine repeat units.

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11 . The block polymer according to any one of the preceding claims, wherein the block polymer comprises one oleophilic block and one surface-anchoring block.

12. The block polymer according to any one of the preceding claims, wherein the block polymer is the product of radical polymerization.

13. The block polymer according to any one of the preceding claims, wherein the block polymer is synthesized by reversible addition-fragmentation chain-transfer (RAFT) polymerization.

14. The block polymer according to any one of the preceding claims, wherein the block polymer is synthesized by atom-transfer radical polymerization (ATRP).

15. Use of a compound according to any one of the preceding claims as a frictionreducing additive in a lubricating composition.

16. The use according to claim 15, wherein the lubricating composition comprises mineral oil.

17. The use according to claim 15, wherein the lubricating composition comprises natural oil.

18. A lubricant composition containing a block polymer according to any one of the preceding claims 1 to 14, and non-polar base oil.

19. The lubricant composition according to claim 18, wherein the concentration of the compound relative to the base oil is 5%-0.01% (w/w), particularly 1 % to 0.05, even more particularly 1 % to 0.1%.

20. Use of a compound according to any one of the preceding claims as a wear-reducing additive in a lubricating composition.

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