THERMOASSOCIATIVE AND EXCHANGEABLE COPOLYMERS, AND COMPOSITION COMPRISING SAME

Abstract

A comb copolymer A2 including at least two boronic ester functions, the copolymer including a main chain and side chains, and at least one portion of the side chains of the copolymer A2 made of oligomers. Also, a composition resulting from mixing at least one polydiol compound A1 and a copolymer A2. The compositions exhibit very varied rheological properties depending on the proportion of the compounds A1 and A2 used. Also, a lubricant composition including such a mixture and at least one lubricating oil. Also, use of this composition to lubricate a mechanical part.

Claims

1-15. (canceled)

16. A comb copolymer A2 comprising at least two boronic ester functional groups, said copolymer comprising a main chain and side chains, at least a portion of the side chains of the copolymer A2 being composed of oligomers comprising more than 30 carbon atoms.

17. The comb copolymer A2 as claimed in claim 16, in which at least a portion of the side chains are composed of oligomers comprising at least 50 carbon atoms.

18. The comb copolymer A2 as claimed in claim 16, in which at least a portion of the side chains of the copolymer A2 are composed of oligomers which exhibit a degree of polymerization ranging from 5 to 1000.

19. The comb copolymer A2 as claimed in claim 16, in which the side chains composed of oligomers comprising more than 30 carbon atoms represent from 3% to 95% by weight, with respect to the total weight of the copolymer A2.

20. The comb copolymer A2 as claimed in claim 16, in which at least a portion of the side chains of the copolymer A2 are composed of oligomers O1 comprising a polyolefin fragment.

21. The comb copolymer A2 as claimed in claim 20, in which the side chains composed of oligomers O1 comprise a polyolefin fragment having from 30 to 500 carbon atoms.

22. The comb copolymer A2 as claimed in claim 20, in which the side chains comprising a polyolefin fragment represent from 3% to 85% by weight, with respect to the total weight of the copolymer A2.

23. The comb copolymer A2 as claimed in claim 20, in which the oligomers O1 are present in the copolymer A2 in the form of repeat units corresponding to one or more monomers M6 of general formula (IX): ##STR00053## in which: Q.sub.1 is chosen from the group consisting of H, CH.sub.3 and CH.sub.2CH.sub.3; Q.sub.2 is chosen from the group consisting of -Q, O-Q, C(O)O-Q, OC(O)-Q, S(CH.sub.2).sub.2C(O)O-Q, S-Q, N(H)C(O)-Q and C(O)N(H)-Q group, with Q is a polyolefin, n represents an integer chosen from 0 and 1, A represents a divalent group chosen from the group consisting of -A.sub.1-, O(-A.sub.2-O).sub.n-A-, C(O)O(-A.sub.2-O).sub.n-A.sub.1-, OC(O)(-A.sub.2-O).sub.n-A.sub.1-, S(-A.sub.2-O).sub.n-A.sub.1-, N(H)C(O)(-A.sub.2-O).sub.n-A.sub.1 and C(O)N(H)(-A.sub.2-O).sub.n-A.sub.1- with: A.sub.1 is a divalent group chosen from the group consisting of a C.sub.1-C.sub.30 alkyl, a C.sub.6-C.sub.30 aryl and a C.sub.6-C.sub.30 aralkyl, A.sub.2 is a divalent group chosen from C.sub.2-C.sub.4 alkyls, n is an integer, n represents 0 or 1.

24. The comb copolymer A2 as claimed in claim 16, comprising at least repeat units corresponding to monomers M4 of formula (IV): ##STR00054## in which: t is an integer equal to 0 or 1; u is an integer equal to 0 or 1; M and R.sub.8 are divalent linking groups, which are identical or different, chosen from the group consisting of a C.sub.6-C.sub.18 aryl, a C.sub.7-C.sub.24 aralkyl and a C.sub.2-C.sub.24 alkyl; X is a functional group chosen from the group consisting of OC(O), C(O)O, C(O)N(H), N(H)C(O), S, N(H), N(R.sub.4) and O, with R.sub.4 a hydrocarbon chain comprising from 1 to 15 carbon atoms; R.sub.9 is chosen from the group consisting of H, CH.sub.3 and CH.sub.2CH.sub.3; R.sub.10 and R.sub.11, which are identical or different, represent a group chosen from the group consisting of a hydrogen atom and a hydrocarbon group comprising from 1 to carbon atoms, optionally substituted by one or more groups chosen from: a hydroxyl or an OJ or C(O)O-J group, with J a hydrocarbon group comprising from 1 to 24 carbon atoms.

25. The comb copolymer A2 as claimed in claim 24, in which the repeat units corresponding to monomers M4 represent from 1 mol % to 50 mol %, with respect to the total number of moles of the monomers of which the copolymer A2 is composed.

26. The comb copolymer A2 as claimed in claim 16, comprising at least repeat units corresponding to monomers M5 of general formula (V): ##STR00055## in which: R.sub.12 is chosen from the group consisting of H, CH.sub.3 and CH.sub.2CH.sub.3, R.sub.13 is chosen from the group consisting of a C.sub.6-C.sub.18 aryl and a C.sub.6-C.sub.15 aryl substituted by a R.sub.13, C(O)OR.sub.13, OR.sub.13, SR.sub.13 and C(O)N(H)R.sub.13 group, with R.sub.13 a C.sub.1-C.sub.30 alkyl group.

27. The comb copolymer A2 as claimed in claim 26, in which the repeat units corresponding to monomers M5 represent from 10 mol % to 90 mol % with respect to the total number of moles of the monomers of which the copolymer A2 is composed.

28. The comb copolymer A2 as claimed in claim 16, which comprises repeat units corresponding to at least one monomer M3 of general formula (X): ##STR00056## in which: Z.sub.1, Z.sub.2 and Z.sub.3, which are identical or different, represent groups chosen from the group consisting of a hydrogen atom, a C.sub.1-C.sub.12 alkyl or an OZ and C(O)OZ group, with Z a C.sub.1-C.sub.12 alkyl.

29. The comb copolymer A2 as claimed in claim 28, in which the monomer M3 is styrene.

30. The comb copolymer A2 as claimed in claim 28, in which the repeat units corresponding to monomers of formula (X) represent from 2 mol % to 50 mol %, with respect to the total number of moles of the monomers of which the copolymer A2 is composed.

31. The comb copolymer A2 as claimed in claim 16, in which the copolymer A2 exhibits a degree of branching ranging from 0.1 mol % to 10 mol %.

32. The comb copolymer A2 as claimed in claim 16, in which the main chain of the comb copolymer A2 has a number-average degree of polymerization ranging from 40 to 2000.

33. A composition resulting from the mixing of at least: a polydiol compound A1, a copolymer A2 as claimed in claim 16.

34. The composition as claimed in claim 33, in which the polydiol compound A1 is a copolymer resulting from the copolymerization: of at least one first monomer M1 of general formula (I): ##STR00057## in which: R.sub.1 is chosen from the group consisting of H, CH.sub.3 and CH.sub.2CH.sub.3; y is an integer equal to 0 or 1; Y represents a divalent linking group chosen from C.sub.1-C.sub.20 alkyl chains, optionally comprising one or more ether O bridges; X.sub.1 and X.sub.2, which are identical or different, are chosen from the group consisting of hydrogen, tetrahydropyranyl, methyloxymethyl, tert-butyl, benzyl, trimethylsilyl and t-butyldimethylsilyl; or else X.sub.1 and X.sub.2 form, with the oxygen atoms, a bridge of following formula: ##STR00058## in which: the stars (*) symbolize the bonds to the oxygen atoms, R.sub.2 and R.sub.2, which are identical or different, are chosen from the group consisting of hydrogen and a C.sub.1-C.sub.11 alkyl group; or else X.sub.1 and X.sub.2 form, with the oxygen atoms, a boronic ester of following formula: ##STR00059## in which: the stars (*) symbolize the bonds to the oxygen atoms, R.sub.2 is chosen from the group consisting of a C.sub.6-C.sub.30 aryl, a C.sub.7-C.sub.30 aralkyl and a C.sub.2-C.sub.30 alkyl; with at least one second monomer M2 of general formula (II): ##STR00060## in which: R.sub.2 is chosen from the group consisting of H, CH.sub.3 and CH.sub.2CH.sub.3, R.sub.3 is chosen from the group consisting of C(O)OR.sub.3; OR.sub.3; SR.sub.3 and C(O)N(H)R.sub.3, with R.sub.3 a C.sub.1-C.sub.30 alkyl group.

35. A lubricating composition resulting from the mixing of at least: a lubricating oil; and a composition as claimed in claim 33.

Description

FIGURES

[0650] FIG. 1 diagrammatically represents a random copolymer (P1), a gradient copolymer (P2) and a block copolymer (P3); each circle represents a monomer motif. The difference in chemical structure between the monomers is symbolized by a different color (light gray/black).

[0651] FIG. 2 diagrammatically represents a comb copolymer.

[0652] FIG. 3 diagrammatically illustrates the reactions for exchanges of boronic ester bonds between two polydiol polymers (A1-1 and A1-2) and two boronic ester polymers (A2-1 and A2-2) in the presence of diols.

[0653] FIG. 4 diagrammatically illustrates and represents the crosslinking of the composition according to the invention in tetrahydrofuran (THF).

[0654] FIG. 5 diagrammatically represents the behavior of the composition of the invention as a function of the temperature. A copolymer (2) having diol functional groups (functional group A) can associate in a thermoreversible way with a copolymer (1) having boronic ester functional groups (functional group B) via a transesterification reaction. The organic group of the boronic ester functional groups (functional group B) which is exchanged during the transesterification reaction is a diol symbolized by a black crescent. A chemical bond (3) of boronic ester type is formed, with release of a diol compound.

[0655] FIGS. 6A, 6B and 6C represent different comb copolymers A2.

[0656] FIG. 7 represents a scheme for the synthesis of comb copolymers A2.

[0657] FIG. 8 represents a scheme for the synthesis of comb copolymers A2.

[0658] FIG. 9 represents a graph which reports the relative viscosity of the compositions A, B and C (ordinate) as a function of the temperature (abscissa) from 10 C. to 150 C.

[0659] FIG. 10 represents a graph which reports the relative viscosity (ordinate) of the compositions B and Bd (obtained from the composition B by dilution of the composition B down to 2.10% by weight of copolymer) as a function of the temperature (abscissa) from 10 to 150 C.

[0660] FIG. 11 represents a graph which reports the relative viscosity (ordinate) as a function of the temperature (abscissa) of the composition Bd during three successive heating-cooling cycles between 10 C. and 150 C. (Bd-1, Bd-2 and Bd-3).

[0661] FIG. 12 represents a graph which reports the relative viscosity (ordinate) as a function of the temperature (abscissa) of the composition C during three successive heating-cooling cycles between 10 C. and 150 C. (C-1, C-2, C-3).

[0662] FIG. 13 represents a graph which reports the relative viscosity (ordinate) of the composition D as a function of the temperature (abscissa) from 10 to 150 C.

[0663] The invention is illustrated by the following non-limiting examples.

EXPERIMENTAL SECTION

[0664] In these examples, the parts and percentages are expressed by weight unless indicated otherwise.

[0665] 1 Synthesis of Comb Copolymers A2 Carrying Boronic Ester Functional Group

[0666] 1.1: Synthesis of the Monomers

1.1.1 Synthesis of the Brominated Monomer (Branching Monomer):

[0667] ##STR00043##

[0668] 7 ml of hydroxyethyl methacrylate (58 mmol), 5.4 ml of pyridine (66 mmol) and 75 ml of dichloromethane are introduced into a 250 ml round-bottomed flask. The round-bottomed flask is then closed using a septum, degassed by bubbling with N.sub.2 for 30 min and then placed in a bath of ice-cold water. 7.7 ml of 2-bromo-2-methyl propionyl bromide (64 mmol) are subsequently added dropwise to the reaction mixture over approximately 15 minutes. The round-bottomed flask is kept stirred for 6 hours. A white precipitate is formed during the reaction. The solution is subsequently filtered in order to remove the solid. The solid is rinsed with dichloromethane (210 ml). The organic phase is subsequently washed 2 times with 100 ml of distilled water, 2 times with 100 ml of a 10% NaHCO.sub.3 solution and then 2 times with 100 ml of a saturated NaCl solution. The organic phase is then dried over MgSO.sub.4 and the solvent removed using a rotary evaporator. 11.6 g of a bright yellow liquid are obtained (yield=72%).

[0669] .sup.1H NMR (CDCl.sub.3): : 6.05 ppm (m, 1H), 5.52 ppm (m, 1H), 4.35 ppm (m, 4H), 1.87 ppm (m, 3H), 1.85 ppm (s, 6H).

[0670] 1.1.2 Synthesis of the Methacrylic Olefinic Macromonomer (Monomer M6-A):

##STR00044##

[0671] 58.8 g (11.6 mmol) of Krasol HLBH 5000M (product supplied by Cray Valley) are dissolved in 150 g of dichloromethane (DCM). 11.9 g of methacrylic anhydride (77.3 mmol), 56.2 mg of 4-dimethylaminopyridine (0.47 mmol) and 7.37 g of trimethylamine (76 mmol) are subsequently added. The solution is left stirring at ambient temperature for 24 h. The solution is subsequently washed 2 times with a 0.5M aqueous sodium hydroxide solution, then 2 times with a 0.5M aqueous hydrochloric acid solution and finally 2 times with distilled water. The organic phase is dried over MgSO.sub.4 and then the solvent is evaporated using a rotary evaporator. The product is subsequently dissolved in tetrahydrofuran (THF) before being precipitated 3 times consecutively from acetone (redissolved in THF before each precipitation). The product is dried under vacuum at 50 C. for 18 hours. A colorless and translucent viscous liquid is thus obtained. The quantitative functionalization of the Krasol (of the alcohol to give methacrylate) is confirmed by .sup.1H NMR by the complete disappearance of the peak between 3.8 and 4.1 ppm, characteristic of the protons in the a position with respect to the alcohol functional group of the Krasol.

[0672] .sup.1H NMR (CDCl.sub.3): : 6.05 ppm (m, 1H), 5.52 ppm (m, 1H), 5.1-4.9 ppm (m, 1H), 1.94 ppm (s, 3H), 2.05-0.48 ppm (1020H), traces of DCM (5.29 ppm), THF (3.75 ppm; 1.84 ppm) and acetone (2.17 ppm).

[0673] 1.1.3 Synthesis of the Olefin Macromonomer Carrying a Terminal Styrene Functional Group (Monomer M6-BOLF1500-St)

[0674] The synthesis of the olefin macromonomer carrying a terminal styrene functional group (OLF1500-St) is carried out in two stages (Schemes 14 and 15) according to the following protocol:

[0675] 1.sup.st Stage

[0676] 4.0 g (27 mmol) of 4-vinylbenzoic acid (4-VBA) are dissolved in 110 ml of anhydrous dichloromethane (DCM) with a catalytic amount (15 drops) of anhydrous dimethylformamide (DMF). 5.8 ml (67 mmol) of oxalyl chloride is subsequently added to the solution. The reaction mixture is left stirring at ambient temperature for 2 hours. After evaporation of the solvent under reduced pressure, the yellow liquid obtained is dried under vacuum for 2 h.

[0677] 2.sup.nd Stage:

[0678] 2.64 g (1.76 mmol) of the olefin copolymer OLF1500 exhibiting a number-average molar mass, M.sub.n, of 1500 g/mol and carrying a terminal primary alcohol functional group and 3.8 ml (27.5 mmol) of NEt.sub.3 are dissolved in 50 ml of anhydrous DCM and the mixture is brought to approximately 0 C. using an ice bath. A solution of 4-vinylbenzoyl chloride obtained during the 1.sup.st stage (27 mmol) in 30 ml of DCM is subsequently added dropwise to the reaction mixture over approximately 25 min. The mixture is stirred in the ice bath for 1 hour and then at ambient temperature for 24 hours. The excess 4-vinylbenzoyl chloride is neutralized by addition of 10 ml of water and by leaving the reaction mixture stirring for 1 hour. The reaction mixture is subsequently successively washed with 3100 ml of a 1M HCl solution, 2100 ml of a 1M NaOH solution and 1100 ml of aqueous sodium chloride solution. After drying the organic phase over MgSO.sub.4, the clear yellow solution obtained is filtered through a basic alumina column. The evaporation of the DCM and the drying under vacuum give 2.80 g (97.6%) of a light yellow oil, the characteristics of which are as follows:

[0679] .sup.1H NMR (400 MHz, CDCl.sub.3) : 8.00 (multiplet, 2H), 7.46 (split doublet, J=1.5 Hz and J=8.3 Hz, 2H), 6.75 (split doublet, J=12.0 Hz and J=17.5 Hz, 1H), 5.86 (split doublet, J=0.8 Hz and J=17.7 Hz, 1H), 5.38 (doublet, J=11.0 Hz, 1H), 4.41-4.28 (multiplet, 2H), 1.83-0.52 (multiplet, 961H).

1.1.4. Synthesis of the Boronic Ester Condensed with 1,2-Dodecanediol Monomer (B-C12Em)
This monomer is obtained according to the protocol described in the application WO2016/113229 (Experimental part 2.1)

[0680] 1.2: Synthesis of the CopolymersMethods

[0681] The number-average molar mass and the dispersity are obtained by size exclusion chromatography using poly(methyl methacrylate) calibration and THF as eluent.

[0682] 1.2.1 Synthesis of a Brominated Main Chain (Brominated Backbone 1):

##STR00045##

[0683] 0.50 g (1.8 mmol) of brominated monomer obtained according to the protocol described above in point 1.1.1 (Scheme 11), 8.52 g (59.9 mmol) of butyl methacrylate, 1.14 g (11.0 mmol) of styrene, 35.8 mg (0.13 mmol) of cumyl dithiobenzoate, 6.3 mg (0.04 mmol) of azobisisobutyronitrile (AIBN) and 5 g of anisole are introduced into a 50 ml Schlenk tube. The reaction medium is stirred and degassed for 30 minutes by bubbling nitrogen through, before being brought to 65 C. for a period of 16 hours. The polymer is subsequently isolated by 3 successive precipitations from methanol and then dried under vacuum at 50 C. for 16 hours. A copolymer exhibiting a number-average molar mass (M.sub.n) of 38 000 g/mol, a dispersity () of 1.2 and a number-average degree of polymerization (DP.sub.n) of approximately 300 is obtained. The polymer thus obtained contains approximately 2.3 mol % (approximately 5% by weight) of brominated methacrylate monomer. These values are respectively obtained by size exclusion chromatography, using THF as eluent and poly(methyl methacrylate) (PMMA) calibration, and by monitoring the conversion of monomers during the copolymerization.

[0684] 1.2.2 Synthesis of Backbones-Dithiobenzoates

##STR00046##

[0685] 835 mg of the brominated backbone 1 (141 mol of brominated monomer) obtained according to the protocol described above ( 1.2.1), 43.6 mg of bis(thiobenzoyl) disulfide (142 mol), 10 mg of copper(I) bromide (CuBr) (69 mol), 29 mg of copper powder (456 mol) and 20 g of toluene are introduced into 100 ml Schlenk round-bottomed flask. The round-bottomed flask is then hermetically sealed using a septum. At the same time, a solution containing 2 ml of toluene and 26 mg of N,N,N,N,N-pentamethyldiethylenetriamine (150 mol) is prepared in a hermetically sealed sample tube. The flask and the sample tube are degassed by bubbling nitrogen through the solutions for 30 minutes. The solution contained in the sample tube is subsequently withdrawn and then injected into the round-bottomed flask using a syringe. The round-bottomed flask is placed in an oil bath thermostatically controlled at 80 C. for 3 days. The solution is subsequently filtered through a basic alumina column in order to remove the copper then concentrated using a rotary evaporator. Finally, the polymer is isolated by 3 successive precipitations from methanol and then dried under vacuum at 50 C. for 20 hours. A copolymer exhibiting a number-average molar mass M.sub.n of 44 000 g/mol and a dispersity D of 1.4 is obtained. These values are obtained by size exclusion chromatography using THF as eluent and a PMMA.

[0686] 1.2.3 Synthesis by RAFT of the Comb Poly(Boronic Ester) (PBB1)

##STR00047##

[0687] 220 mg (39 mol of dithiobenzoate monomer) of backbone-dithiobenzoate 1 obtained according to the protocol described above in 1.2.2, 5.71 g (16.9 mmol) of stearyl methacrylate, 0.79 g (1.5 mmol) of boronic ester monomer obtained according to the protocol described in the patent application WO2016/113229 (Experimental part 2.1), 1.72 mg (10.5 mol) of AIBN and 7 g of anisole are introduced into a 50 ml Schlenk tube. The reaction medium is stirred and degassed for 30 min by bubbling nitrogen through, before being brought to 65 C. for a period of 8.5 hours. Finally, the polymer is isolated by 3 successive precipitations from anhydrous acetone and then dried under vacuum at 50 C. for 20 hours. A copolymer exhibiting a number-average molar mass M.sub.n of 137 000 g/mol and a dispersity of 2.4 is obtained. These values are obtained by size exclusion chromatography using THF as eluent and a PMMA calibration. According to the conversion of monomers determined by .sup.1H NMR, the pendant chains have a number-average degree of polymerization DP.sub.n of approximately 165.

[0688] 1.2.4 Synthesis of a Comb Copolymer of Butyl Methacrylate, of Styrene Carrying a Boronic-C.sub.12 Ester Functional Group and of the Olefin Macromonomer M6-B-OLF1500-St (PBB2)

##STR00048##

[0689] The synthesis of the comb copolymer carrying boronic ester functional groups in the main chain PBB2 is carried out according to the following protocol:

[0690] 2.50 g (17.5 mmol) of butyl methacrylate (BMA), 0.39 g (0.87 mmol) of boronic ester monomer condensed with 1,2-didecanediol (B-C12Em) obtained according to the protocol described in application WO2016/113229 (Experimental part 2.1), 0.89 g (0.93 mmol) of the olefin macromonomer M6-B-OLF1500-St obtained according to the protocol described in section 1.1.3 above, 9.3 mg (0.04 mmol) of RAFT transfer agent 2-cyano-2-propyl benzodithioate (PPBD), 2.8 mg (0.02 mmol) of AIBN and 3.8 ml of anisole are introduced into a 25 ml Schlenk tube. The reaction medium is stirred and degassed for 30 min by bubbling nitrogen through, before being brought to 65 C. for a period of 19 hours.

[0691] After 19 h of polymerization, the Schlenk tube is placed in an ice bath in order to halt the polymerization. The polymer is subsequently isolated by a precipitation from acetone cooled using an ice bath, separation by settling of the supernatant and drying of the pasty polymer phase under vacuum at 50 C. overnight. The copolymer thus obtained exhibits a number-average molar mass (M.sub.n) of 54 800 g/mol, a dispersity () of 1.23 and a number-average degree of polymerization (DP.sub.n) of 280. The first two values are obtained by size exclusion chromatography using THF as eluent and poly(methyl methacrylate) calibration, while the DP.sub.n is obtained by .sup.1H NMR monitoring of the conversion of monomers during polymerization.

[0692] A poly(butyl methacrylate-co-EB-C.sub.12-co-OLF15000CP) copolymer PBB2 containing 5.7 mol % of repeat units EB-C.sub.12 (12% by weight) and 6.8 mol % of pendant OLF1500-OCP chains (30% by weight) is obtained.

[0693] 1.2.5 Synthesis of a Comb Copolymer of Butyl Methacrylate, of Olefin Macromonomer M6-B-OLF1500-St and of Pendant Poly(Boronic Ester) Polymeric Chains (PBB3)

[0694] The synthesis of the comb copolymer containing the olefin macromonomer M6-B-OLF1500-St and pendant poly(boronic ester) polymeric chains (PBB3) is carried out according to the following protocol (Scheme 15 below):

##STR00049## ##STR00050## ##STR00051##

[0695] 1.2.5.1 Synthesis of a Main Chain Containing Olefin Macromonomer M6-B-OLF1500-St and 2-Xanthate Ethyl Methacrylate (M6-B-OLF1500-St-Co-Xanthate Backbone)

[0696] 4.00 g (28.1 mmol) of butyl methacrylate, 1.30 g (1.36 mmol) of the olefin macromonomer M6-B-OLF1500-St, 1.06 g (4.52 mmol) of 2-xanthate ethyl methacrylate (XEMA; synthesized according to the protocol described in the paper Synthesis of Well-Defined Polythiol Copolymers by RAFT Polymerization, R. Nicola, Macromolecules, 2012, 45, 821-827), 16.4 mg (0.074 mmol) of RAFT transfer agent 2-cyano-2-propyl benzodithioate (PPBD), 4.8 mg (0.030 mmol) of azobisisobutyronitrile (AIBN) and 6.4 ml of anisole are introduced into a 50 ml Schlenk tube. The reaction medium is stirred and degassed for 30 min by bubbling nitrogen through, before being brought to 65 C. for a period of 20.5 hours.

[0697] After 20.5 h of polymerization, the Schlenk tube is placed in an ice bath in order to halt the polymerization. The polymer is subsequently isolated by 2 successive precipitations from methanol cooled using an ice bath, filtration and drying under vacuum at 50 C. overnight. The copolymer thus obtained exhibits a number-average molar mass (M.sub.n) of 80 600 g/mol, a dispersity () of 1.61 and a number-average degree of polymerization (DP.sub.n) of 350. The first two values are obtained by size exclusion chromatography using THF as eluent and poly(methyl methacrylate) calibration, while the DP.sub.n is obtained by .sup.1H NMR monitoring of the conversion of monomers during polymerization.

[0698] A poly(butyl methacrylate-co-2-xanthate ethyl methacrylate-co-M6-B-OLF1500-St) copolymer, M6-B-OLF1500-St-co-xanthate backbone, containing 7.9 mol % of 2-xanthate ethyl methacrylate repeat units (9.5% by weight) and 5.6 mol % of pendant OLF1500-OCP chains (27% by weight), is obtained.

[0699] 1.2.5.2 Synthesis of a Main Chain Containing Olefin Macromonomer M6-B-OLF1500-St and Pendant Acrylate Functional Groups (M6-B-OLF1500-St-Co-Acrylate Backbone)

[0700] The xanthate functional groups of the M6-B-OLF1500-St-co-xanthate backbone copolymer are subsequently converted into acrylates by Michael addition with 1,6-hexanediol diacrylate according to the following protocol:

[0701] 3.70 g (1.50 mmol of XEMA functional groups) of M6-B-OLF1500-St-co-xanthate backbone are introduced into a 250 ml Schlenk tube and dissolved in 35 ml of a THF:DMF=1:1 by volume mixture. 0.44 g (6.00 mmol) of n-butylamine and three drops of tributylphosphine are introduced into the Schlenk tube. The reaction medium is degassed for 10 min by bubbling nitrogen through, then stirred at ambient temperature for 2 hours. Subsequently, a solution of 6.79 g (30.0 mmol) of 1,6-hexanediol diacrylate in 3 ml of THF is introduced and the reaction medium is left stirring at ambient temperature for a period of 48 hours.

[0702] The reaction medium is subsequently concentrated under vacuum and the polymer is isolated by 3 successive precipitations from methanol cooled using an ice bath, filtration and drying under vacuum at 50 C. overnight. The copolymer thus obtained exhibits a number-average molar mass (M.sub.n) of 60 100 g/mol and a dispersity (D) of 1.65, as obtained by size exclusion chromatography using THF as eluent and poly(methyl methacrylate) calibration.

[0703] The M6-B-OLF1500-St-co-acrylate backbone copolymer, containing 5.1 mol % of repeat units carrying a pendant acrylate functional group (9.4% by weight) and 5.6 mol % of pendant OLF1500-OCP chains (27% by weight), as measured by .sup.1H NMR, is obtained.

[0704] 1.2.5.3 Synthesis of a Precursor of Side Chains by Copolymerization of Lauryl Methacrylate, of Boronic Ester Monomer Condensed with 1,2-Dodecanediol (B-C12Em) Obtained According to the Protocol Described in Application WO2016/113229 (Experimental Part 2.1) (Poly(Boronic Ester) Side Chain)

[0705] The pendant poly(boronic ester) polymeric chains of the comb copolymer containing the olefin macromonomer M6-B-OLF1500-St and pendant poly(boronic ester) polymeric chains (PBB3) are prepared according to the following protocol (Scheme 15 above):

[0706] 5.00 g (19.6 mmol) of lauryl methacrylate (LMA), 2.20 g (4.91 mmol) of boronic ester monomer condensed with 1,2-dodecanediol (B-C12Em), 155 mg (0.70 mmol) of RAFT transfer agent PPBD, 5.8 mg (0.035 mmol) of AIBN and 2.0 ml of anisole are introduced into a 25 ml Schlenk tube. The reaction medium is stirred and degassed for 30 min by bubbling nitrogen through, before being brought to 65 C. for a period of 24 hours.

[0707] After 24 h of polymerization, the Schlenk tube is placed in an ice bath in order to halt the polymerization. The polymer is subsequently isolated by a precipitation from acetone cooled using an ice bath, separation by settling of the supernatant and drying of the polymer phase under vacuum at 50 C. overnight. The copolymer thus obtained exhibits a number-average molar mass (M.sub.n) of 10 700 g/mol, a dispersity () of 1.31 and a number-average degree of polymerization (DP.sub.n) of 26. The first two values are obtained by size exclusion chromatography using THF as eluent and poly(methyl methacrylate) calibration, while the DP.sub.n is obtained by .sup.1H NMR monitoring of the conversion of monomers during polymerization.

[0708] A poly(lauryl methacrylate-co-EB-C.sub.12) copolymer, poly(boronic ester) side chain, containing 21 mol % of repeat units B-C.sub.12Em (32% by weight) and 79 mol % of lauryl methacrylate repeat units (68% by weight) is obtained.

[0709] 1.2.5.4 Synthesis of the Comb Copolymer Containing the Olefin Macromonomer M6-B-OLF1500-St and Pendant Poly(Boronic Ester) Polymeric Chains (PBB3)

[0710] 145 g (0.015 mmol) of poly(boronic ester) side chain copolymer prepared according to the protocol described in 1.2.5.3 are introduced into a 25 ml Schlenk tube and dissolved in 2.0 ml of a THF:DMF=2:1 by volume mixture. 5 mg (0.06 mmol) of n-butylamine and three drops of tributylphosphine are added to the solution. The reaction medium is degassed for 3 min by bubbling nitrogen through and stirred at ambient temperature for 2 hours. Subsequently, a solution of 200 mg (0.05 mmol of acrylate functional groups) of M6-B-OLF1500-St-co-acrylate backbone copolymer prepared according to the protocol described in 1.2.5.2 in 2.5 ml of a THF:DMF=2:1 by volume mixture is added to the reaction mixture under a nitrogen atmosphere. The reaction mixture is subsequently brought to 40 C. for a period of 40 hours.

[0711] After 40 h of the reaction, 15 mg (0.24 mmol) of ethanethiol are added to the reaction medium, which is kept stirred at ambient temperature for 4 hours.

[0712] The comb copolymer containing the olefin macromonomer M6-B-OLF1500-St and pendant poly(boronic ester) polymeric chains (PBB3) is subsequently isolated by precipitation from acetone cooled using an ice bath, separation by settling of the supernatant and drying under vacuum at 50 C. overnight.

[0713] 1.3: Synthesis of the Comparative CopolymersMethods

[0714] 1.3.1 Random Linear Poly(Boronic Ester) Copolymer (LPBComparative)

[0715] This copolymer comprises 6.0 mol % of B-C.sub.12E repeat units (10% by weight). The mean side chain length is 12 carbon atoms. Its number-average molar mass is 45 700 g/mol. Its dispersity is 1.39. Its number-average degree of polymerization (DP.sub.n) is 175. The number-average molar mass and the dispersity are obtained by size exclusion chromatography using poly(methyl methacrylate) calibration and THF as eluent. This copolymer is obtained according to the protocol described in section 2 of the Experimental part of the application WO2016/113229.

[0716] 1.4 Synthesis of the Diol CopolymersMethods

[0717] 1.4.1 Linear Polydiol (LPDiol):

The linear polydiol was synthesized according to the protocol described in the application FR 1 661 400 or WO2018096252A1 (Experimental part 1.2.).
This copolymer comprises 7.0 mol % of monomer carrying a diol functional group (6.0% by weight). The mean side chain length is 10.3 carbon atoms. Its number-average molar mass is 40 000 g/mol. Its dispersity is 1.46. Its number-average degree of polymerization (DP.sub.n) is 170.

1.4.2 Synthesis of a Copolymer of Butyl Methacrylate, of Methacrylate Carrying a Diol Functional Group and of the Olefin Macromonomer OLF1500-St (CPDiol)

[0718] ##STR00052##

[0719] The synthesis of the comb copolymer carrying diol functional groups in the main chain CPDiol is carried out according to the following protocol (scheme 16 above:

[0720] 2.50 g (17.5 mmol) of butyl methacrylate (BMA), 0.18 g (0.89 mmol) of methacrylate monomer carrying a diol function group, 0.89 g (0.93 mmol) of the olefin macromonomer M6-B-OLF1500-St obtained according to the protocol described in section 1.1.4 above, 9.3 mg (0.04 mmol) of RAFT transfer agent 2-cyano-2-propyl benzodithioate (PPBD), 2.8 mg (0.02 mmol) of azobisisobutyronitrile (AIBN) and 3.6 ml of anisole are introduced into a 25 ml Schlenk tube. The reaction medium is stirred and degassed for 30 min by bubbling nitrogen through, before being brought to 65 C. for a period of 19 hours.

[0721] After 19 h of polymerization, the Schlenk tube is placed in an ice bath in order to halt the polymerization. The polymer is subsequently isolated by 2 successive precipitations from methanol cooled using an ice bath, filtration and drying under vacuum at 50 C. overnight. The copolymer thus obtained exhibits a number-average molar mass (M.sub.n) of 65 500 g/mol, a dispersity () of 1.25 and a number-average degree of polymerization (DP.sub.n) of 350. The first two values are obtained by size exclusion chromatography using THF as eluent and poly(methyl methacrylate) calibration, while the DP.sub.n is obtained by .sup.1H NMR monitoring of the conversion of monomers during polymerization.

[0722] A poly(butyl methacrylate-co-alkyldiol methacrylate-co-OLF1500 OCP) copolymer CPDiol containing 4.5 mol % of diol repeat units (4.6% by weight) and 6.8 mol % of OLF1500-OCP pendant chains (32% by weight) is obtained. The mean length of the side chains is 10.9 atoms of carbon.

[0723] 2. Preparation of the Compositions

[0724] Each polymer is dissolved in a Group III base oil in order to obtain a 10% by weight polymer solution. After complete dissolution of the polymer in the oil, these solutions serve as mother solutions for the preparation of the formulations to be studied in rheology.

[0725] 2.1 Ingredients for the Formulation of Compositions

[0726] Lubricating Base Oil

[0727] The lubricating base oil used in the compositions to be tested is an oil from Group III of the API classification, sold by SK under the name Yubase 4. It exhibits the following characteristics: [0728] its kinematic viscosity at 40 C., measured according to the standard ASTM D445, is 19.57 cSt; [0729] its kinematic viscosity measured at 100 C. according to the standard ASTM D445 is 4.23 cSt; [0730] its viscosity index, measured according to the standard ASTM D2270, is 122; [0731] its Noack volatility as percentage by weight, measured according to the standard DIN 51581, is 15; [0732] its flash point in degrees Celsius, measured according to the standard ASTM D92, is 230 C.; [0733] its pour point in degrees Celsius, measured according to the standard ASTM D97, is 15 C.

[0734] Composition A (Comparative) is Obtained as Follows:

[0735] 0.53 g of the 39.2% by weight solution of LPB in the Group III base oil are mixed with 6.76 g of this same base oil. This mixture is kept stirred in a vortex mixer at ambient temperature for 1 minute. The solution thus obtained of LPB is subsequently mixed with 0.71 g of the 25.4% by weight solution of LPDiol in the Group III base oil. The mixture thus obtained is kept stirred in a vortex mixer at ambient temperature for 2 minutes. A solution comprising 2.60% by weight of linear copolymer LPB and 2.25% by weight of linear copolymer LPDiol is obtained.

[0736] Composition B (According to the Invention) is Obtained as Follows:

0.60 g of brush poly(boronic ester) copolymer PBB2 and 5.40 g of Group III base oil are introduced into a flask. The mixture thus obtained is kept stirred at 100 C. until the poly(boronic ester) PBB2 has completely dissolved. A 10% by weight solution of brush poly(boronic ester) copolymer PBB2 is thus obtained.
0.60 g of brush polydiol copolymer CPDiol and 5.40 g of Group III base oil are introduced into a flask. The mixture thus obtained is kept stirred at 100 C. until the brush polydiol copolymer CPDiol has completely dissolved. A 10% by weight solution of brush polydiol copolymer CPDiol is thus obtained.

[0737] 1.47 g of the 10% by weight solution of poly(boronic ester) PBB2 in the Group III base oil are mixed with 2.94 g of this same base oil. This mixture is kept stirred in a vortex mixer at ambient temperature for 1 minute. The solution thus obtained of PBB2 is subsequently mixed with 1.47 g of the 10% by weight solution of polydiol CPDiol in the Group III base oil and kept stirred in a vortex mixer at ambient temperature for 2 minutes. Composition B, containing 2.50% by weight of brush poly(boronic ester) copolymer PBB2 and 2.50% by weight of brush polydiol copolymer CPDiol, is thus obtained.

[0738] Composition C (According to the Invention) is Obtained in the Following Manner:

[0739] 1.47 g of the 10% by weight solution of brush poly(boronic ester) copolymer PBB2 prepared above are mixed with 3.83 g of Group III base oil. This mixture is kept stirred in a vortex mixer at ambient temperature for 1 minute. The solution thus obtained of PBB2 is subsequently mixed with 0.58 g of the 25.4% by weight solution of LPDiol in the Group III base oil and kept stirred in a vortex mixer at ambient temperature for 2 minutes. A solution comprising 2.50% by weight of brush poly(boronic ester) copolymer PBB2 and 2.50% by weight of linear polydiol copolymer LPDiol is thus obtained.

[0740] Composition D (According to the Invention) is Obtained in the Following Manner:

3.82 g of the 10% by weight solution of poly(boronic ester) PBB2 in the Group III base oil are mixed with 2.06 g of this same base oil. This mixture is kept stirred in a vortex mixer at ambient temperature for 1 minute. The composition D containing 6.50% by weight of brush poly(boronic ester) copolymer PBB2 is thus obtained.

[0741] 3. Rheology of the Solutions of Polymers

[0742] The rheological studies were carried out using a rheometer of the stress-controlled Couette MCR 501 type from Anton Paar.

[0743] The rheology measurements were carried out using a cylindrical geometry of DG 26.7 reference. The viscosity was measured as a function of the shear rate for a temperature range varying from 10 C. to 150 C. For each temperature, the viscosity of the system was measured as a function of the shear rate from 1 to 100 s.sup.1. The measurements of viscosity as a function of the shear rate at T=10 C., 40 C., 70 C., 100 C., 130 C. and 150 C. were carried out (ranging from 10 C. to 150 C.). A mean viscosity was then calculated for each temperature using the measurement points located on the same plate (from 15 to 100 s.sup.1).

The relative viscosity, calculated according to the following formula

[00001]$\left({}_{\mathrm{relative}}=\frac{{}_{\mathrm{solution}}}{{}_{\mathrm{base}.Math..Math.\mathrm{oil}}}\right)$

[0744] was chosen to represent the change in the viscosity of the system as a function of the temperature because this quantity directly reflects the compensation for the loss of natural viscosity of a Group III base oil of the polymer systems studied. Table 1 below shows the change in the absolute viscosities of the compositions A to C as a function of temperature.

[0745] 3.2 Results Obtained in Rheology

[0746] The relative viscosities of the compositions B and C were studied over a range of temperatures extending from 10 C. to 150 C. and compared with that of the composition A. The viscosity of the solution was calculated by taking the mean of the absolute viscosities obtained for the shear rates between 15 and 100 s.sup.1. The relative viscosity of these compositions is shown in FIG. 9.

TABLE-US-00002 TABLE 1 [mPa .Math. s] [mPa .Math. s] [mPa .Math. s] Temperature [mPa .Math. s] Composition Composition Composition [ C.] Yubase 4 A B C 10 63.4 99.9 82.1 86.4 40 16.4 27.2 21.8 23.4 70 6.61 11.4 8.84 9.89 100 3.45 6.18 4.80 5.45 130 2.10 3.89 3.14 3.52 150 1.60 2.98 2.53 2.74

[0747] When the linear polydiol LPDiol and the linear poly(boronic ester) LPB are present together in the same lubricating composition (composition A), a significant compensation for the loss of natural viscosity of the Group III base oil over the entire range of the temperatures studied is observed. This is reflected by a virtually linear increase in the relative viscosity between 10 C. and 150 C. (FIG. 11, dashed line-hollow squares). However, the composition A also impacts the cold viscosity of the formulation, with a relative viscosity at 10 C. of 1.58.

[0748] The presence of the comb polydiol copolymer CPDiol and of the comb poly(boronic ester) copolymer PBB2 in the same lubricating composition (composition B) makes possible a significant reduction in the relative viscosity at low temperature, down to .sub.rel=1.30 at 10 C. At the same time, a lower compensation of this formulation for the loss of natural viscosity of the Group III base oil at high temperatures is observed, compared to the formulation A (FIG. 9, dashed/continuous line-stars).

[0749] The dilution of the composition B down to 2.10% by weight of brush polydiol copolymer CPDiol and 2.10% by weight of brush poly(boronic ester) copolymer PBB2 makes it possible to further reduce the relative viscosity at 10 C. down to .sub.rel=1.21 (FIG. 10-Bd, dotted line-stars). However, unlike the compositions containing linear copolymers, even having this low relative viscosity under cold conditions, the composition Bd preserves its viscosifying behavior at high temperatures (.sub.rel=1.43 at 150 C.). The relative viscosity values are represented for three successive heating-cooling cycles between 10 C. and 150 C. (Bd-1, Bd-2 and Bd-3). These change in a negligible way during the 3 cycles and always give an increase in the relative viscosity between 10 C. and 150 C. (FIG. 11).

[0750] When the comb poly(boronic ester) copolymer PBB2 and the linear polydiol LPDiol are present together in the same lubricating composition (composition C), the advantages of the two systems are combined. On this intersecting of the types of structure of associative copolymers, a satisfactory compensation for the loss of natural viscosity of the base oil over the temperature range from 100 C. to 150 C. is observed (FIG. 9, continuous line-solid squares), which occurs in combination with a sharp decrease in the relative viscosity at low temperature, in comparison with the formulation containing only linear copolymers (decrease in the relative viscosity at 10.sup.0 of from 1.58 to 1.36).

[0751] The relative viscosity values are also represented for three successive heating-cooling cycles between 10 C. and 150 C. (C-1, C-2 and C-3). These change very little during the 3 cycles and always give an increase in the relative viscosity of approximately 0.4 between 10 C. and 150 C., reflecting the good compensation for the natural loss of viscosity of the Group III base oil over this range of temperatures (FIG. 12).

[0752] The poly(boronic ester) brush copolymer PBB2 alone in the Group III base oil at a concentration of 6.50% by weight (composition D) does not contribute as great a compensation as the formulations B and C for the loss of natural viscosity of the Group III base oil (FIGS. 13 and 9) but it makes it possible, however, to change from a relative viscosity of 1.4 at 10 C. to 1.50 at 150 C.