Controlled free-radical polymerization of N-vinyl lactams in an aqueous medium

Abstract

The present invention relates to a method for preparing a polymer based on N-vinyl lactam monomer units, which comprises a step (E) for controlled radical polymerization of a composition comprising: monomers containing (and most often consisting of) N-vinyl lactam monomers, either identical or different (and generally identical); an agent for controlling the radical polymerization, for example comprising a thiocarbonylthio group S(CS); and a radical polymerization initiator which is a redox system comprising a reducing agent (Red) and an oxidizing agent (Ox).

Claims

1. A method for preparing a polymer based on N-vinyl lactam monomer units, which comprises a controlled radical polymerization step (E) for a composition comprising: monomers containing N-vinyl lactam monomers either identical or different; and a control agent for the radical polymerization; and a radical polymerization initiator which is a redox system, comprising a reducing agent and an oxidizing agent, wherein the difference between the standard redox potentials of the oxidizer and of the reducing agent (E.sub.ox-E.sub.red) is of at least 1V; wherein the control agent is a compound bearing a xanthate function S(CS)O.

2. The method according to claim 1, wherein step (E) is conducted in an aqueous medium.

3. The method according to claim 1, wherein the difference between the standard redox potentials of the oxidizer and of the reducing agent (E.sub.ox-E.sub.red) is of at least 1.2V.

4. The method according to claim 1, wherein the control agent is O-ethyl-S-(1-methoxycarbonyl ethyl) xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OCH.sub.2CH.sub.3).

5. The method according to claim 1, wherein, in step (E), the N-vinyl lactam monomers are N-vinylpyrrolidone monomers (NVP).

6. The method according to claim 1, wherein step (E) is conducted at a temperature below 40 C.

7. The method according to claim 6, wherein step (E) is conducted at room temperature.

8. The method according to claim 1, wherein the oxidation standard redox potential Eox of the oxidizing agent applied in step (E) is less than that of the N-vinyl lactam monomers used.

9. The method according to claim 8, wherein, in step (E), the oxidizing agent used is tertbutyl hydroperoxide (t-BuOOH).

10. The method according to claim 1, wherein, in step (E), the reducing and oxidizing agents have a pKa of more than 4.

11. The method according to claim 1, wherein, in step (E), the reducing agent is sodium sulfite.

12. The method according to claim 1, wherein, in step (E), the reducing agent is ascorbic acid.

13. The method according to claim 1, wherein, in step (E), the oxidizing agent used is tertbutyl hydroperoxide (t-BuOOH) and the reducing agent is sodium sulfite.

14. The method according to claim 1, wherein, in step (E), the oxidizing agent used is tertbutyl hydroperoxide (t-BuOOH) and the reducing agent is ascorbic acid.

15. The method according to claim 1, for the synthesis of sequenced copolymers, which includes, after step (E), a step (E1) for controlled radical polymerization of a mixture comprising: all or part of the polymer as obtained at the end of step (E); ethylenically unsaturated monomers; and a source of free radicals.

16. The method according to claim 1, wherein the control agent is a compound bearing an O-ethyl xanthate function of formula S(CS)OCH.sub.2CH.sub.3.

17. The method according to claim 1, wherein the reducing agent and the oxidizing agent are separately introduced into the medium of step (E).

18. The method according to claim 1, wherein step (E) is conducted (i) first by forming a mixture comprising one of the oxidizing or reducing agents in a mixture with the monomers and the control agents and then (ii) by adding to this mixture the other of the oxidizing or reducing agents.

Description

EXAMPLE 1

Synthesis According to the Invention of a poly(NVP) of Low Molar Massa Tertbutyl Hydroperoxide/Sodium Sulfite Pair

(1) In a 15 mL Schlenk at room temperature (20 C.), 2 g of N-vinylpyrrolidone, 1 g of distilled water, 150 mg of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 40 mg of a solution of tertbutyl hydroperoxide (70% by mass in water) are introduced.

(2) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes. Next 40 mg of sodium sulfite were added in one go under an argon stream.

(3) The reaction medium was left with stirring for 24 hours at room temperature.

(4) At the end of the reaction, a 92% conversion was determined by .sup.1H NMR. The presence of the xanthate end is also observed in .sup.1H NMR.

(5) A steric exclusion chromatography analysis in DMF additive with LiCl (0.1N) with a relative calibration of poly(methyl methacrylate) provides the following values of the number average molar mass (M.sub.n) and of the polymolecularity index (M.sub.w/M.sub.n):
M.sub.n=3,600 g/mol M.sub.w/M.sub.n=1.18.

(6) A MALDI-TOF spectrometry analysis with the 4-(4-nitrophenylazo)resorcinol matrix without any cationizing agent confirms the structure of the expected polymer.

EXAMPLE 2

Synthesis According to the Invention of a poly(NVP) with a High Molar MassTertbutyl Hydroperoxide/Sodium Sulfite Pair

(7) In a 15 mL Schlenk at room temperature (20 C.), 2 g of N-vinylpyrrolidone, 1 g of distilled water, 43 mg of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 40 mg of a solution of tertbutyl hydroperoxide (70% by mass in water) are inroduced.

(8) The reaction mixture was degassed with extra argon bubbling for 30 minutes.

(9) Next 40 mg of sodium sulfite were added in one go under an argon stream.

(10) The reaction medium was left with stirring for 24 hours at room temperature.

(11) At the end of the reaction, an 89% conversion was determined by .sup.1H NMR.

(12) The presence of the xanthate end is also observed in .sup.1H NMR.

(13) A steric exclusion chromatography analysis in DMF additive with LiCl (0.1N) with a relative calibration of poly(methyl methacrylate) provides the following values of the number average molar mass (M.sub.n) and of the polymolecularity index (M.sub.w/M.sub.n):
M.sub.n=22,700 g/mol M.sub.wM.sub.n=1.4

EXAMPLE 3

Synthesis According to the Invention of a poly(NVP) with a Low Molar MassTertbutyl Hydroperoxide/Ascorbic Acid Pair

(14) In a 15 mL Schlenk at room temperature (20 C.), 2 g of N-vinylpyrrolidone, 1 g of distilled water, 230 mg of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 40 mg of a solution of tertbutyl hydroperoxide (70% by mass in water) are introduced.

(15) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes.

(16) Next 45 mg of ascorbic acid were added in one go under an argon stream.

(17) The reaction medium was left with stirring for 24 hours at room temperature.

(18) At the end of the reaction, an 98% conversion was determined by .sup.1H NMR.

(19) The presence of the xanthate end is also observed in .sup.1H NMR.

(20) A steric exclusion chromatography analysis in DMF additive with LiCl (0.1N) with a relative calibration of poly(methyl methacrylate) provides the following values of the number average molar mass (M.sub.n) and of the polymolecularity index (M.sub.w/M.sub.n):
M.sub.n=3,100 g/mol M.sub.w/M.sub.n=1.18.

(21) A MALDI-TOF spectrometry analysis with the 4-(4-nitrophenylazo)resorcinol matrix without any cationizing agent confirms the structure of the expected polymer.

EXAMPLE 4

Synthesis According to the Invention of a poly(NVP) with a High Molar MassTertbutyl Hydroperoxide/Ascorbic Acid Pair

(22) In a 15 mL Schlenk at room temperature (20 C.), 4 g of N-vinylpyrrolidone, 2 g of distilled water, 21 mg of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 80 mg of a tertbutyl hydroperoxide solution (70% by mass in water) are introduced.

(23) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes. Next 90 mg of ascorbic acid were added in one go under an argon stream.

(24) The reaction medium was left with stirring for 24 hours at room temperature.

(25) At the end of the reaction, an 89% conversion was determined by .sup.1H NMR.

(26) The presence of the xanthate end is also observed in .sup.1H NMR.

(27) A steric exclusion chromatography analysis in DMF additive with LiCl (0.1N) with a relative calibration of poly(methyl methacrylate) provides the following values of the number average molar mass (M.sub.n) and of the polymolecularity index (M.sub.w/M.sub.n):
M.sub.n=25,500 g/mol M.sub.w/M.sub.n=1.5

EXAMPLE 5

Synthesis According to the Invention of a poly(acrylic acid)-b-poly(N-vinyl pyrrolidone) Diblock CopolymerTertbutyl Hydroperoxide/Sodium Sulfite Pair

5.1: Synthesis of a Live poly(acrylic acid)polymer with a Xanthate End (Polymer P5)

(28) In a 15 mL flask at room temperature, 4 g of acrylic acid, 1.5 g of distilled water, 2 g of ethanol, 1 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 25 mg of 4,4-azobis(4-cyanovaleric) acid are introduced.

(29) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes.

(30) The flask was then placed in a thermostated oil bath at 60 C. and the medium was left with stirring at this temperature for 3 hours.

(31) At the end of the reaction, a 98% conversion was determined by .sup.1H NMR.

(32) A number molar mass M.sub.n=800 g/mol is calculated by .sup.1H NMR for the thereby prepared polymer P5.

5.2: Synthesis of the Diblock Copolymer (Use of P5 as a Control Agent)

(33) The reaction mixture from step 5.1 was dried in vacuo and then taken up in ethanol and precipitated from diethylether. The obtained precipitate was dried in vacuo for 24 hours in order to remove the residual solvents, whereby a polymer P5 is obtained as a powder.

(34) 105 mg of this powder were introduced into a 15 mL Schlenk at room temperature, and then 1 g of N-vinylpyrrolidone, 2 g of distilled water and 40 mg of a solution of tertbutyl hydroperoxide (70% by mass in water) were added.

(35) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes.

(36) Next, 40 mg of sodium sulfite were added in one go under an argon stream. The reaction was left with stirring for 24 hours at room temperature.

(37) At the end of the reaction a 100% conversion was determined by .sup.1H NMR.

(38) By comparing the analysis with DOSY NMR of the polymer P5 and of the copolymer from the example, the diblock nature of the copolymer is confirmed by considering the difference in the diffusion coefficients (D in m.sup.2/s) between P5 and the final copolymer. For P5, D=203 m.sup.2/s while for the PAA-PVP diblock, D=89 m.sup.2/s. Further, the DOSY 2D map of the two samples gives the possibility of viewing that P5 has totally reacted during the step for polymerization of NVP, in order to be incorporated into the PAA-PVP diblock.

EXAMPLE 6

Synthesis According to the Invention of a poly(2-acrylamido-2-methylpropane-sulfonic acid)-b-poly(N-vinyl pyrrolidone) Diblock CopolymerTertbutyl Hydroperoxide/Sodium Sulfite Pair

6.1: Synthesis of a Live poly(2-acrylamido-2-methylpropane-sulfonic acid)polymer with a Xanthate End (Polymer P6)

(39) In a 25 mL flask at room temperature, 8 g of a 2-acrylamido-2-methylpropane-sulfonic acid solution (50% by mass in water), 4 g of ethanol, 1 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 25 mg of 4,4azobis(4-cyanovaleric)acid were introduced.

(40) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes

(41) The flask was then placed in a thermostated oil bath at 60 C. and the medium was left with stirring at this temperature for 3 hours.

(42) At the end of the reaction, a 97% conversion was determined with .sup.1H NMR.

(43) A number molar mass M.sub.n=1,800 g/mol is calculated by .sup.1H NMR for the thereby prepared polymer P6.

6.2: Synthesis of the Diblock Copolymer

(44) The reaction mixture from step 6.1 was dried in vacuo and then taken up in ethanol and precipitated from diethylether. The obtained precipitate was dried in vacuo for 24 hours in order to remove the residual solvents, whereby the polymer P6 was obtained as a powder.

(45) 110 mg of this powder were introduced into a 15 mL Schlenk at room temperature, and then 1 g of N-vinylpyrrolidone, 2 g of distilled water and 40 mg of a tertbutyl hydroperoxide solution (70% by mass in water) were added.

(46) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes.

(47) Next, 40 mg of sodium sulfite were added in one go under an argon stream. The reaction was left with stirring for 24 hours at room temperature.

(48) At the end of the reaction, a 99% conversion was determined by .sup.1H NMR.

(49) By comparing the DOSY NMR analysis of the polymer P6 and of the copolymer from the example, the diblock nature of the copolymer is confirmed by considering the difference in the diffusion coefficients (D in m.sup.2/s) between P6 and the final copolymer. For P6, D=260 m.sup.2/s while for the PAA-PVP diblock, D=66 m.sup.2/s. Further, the DOSY 2D map of both samples gives the possibility of viewing that P6 has totally reacted during the step for polymerization of NVP, in order to be incorporated into the PAMPS-PVP diblock.

EXAMPLE 7

Synthesis According to the Invention of a poly(acrylamidopropyl-trimethylammonium chloride)-b-poly(N-vinyl pyrrolidone)Tertbutyl Hydroperoxide/Sodium Sulfite Pair

7.1: Synthesis of a Live poly(acrylamidopropyltrimethylammonium chloride)polymer with a Xanthate End (Polymer P7)

(50) In a 25 mL flask, at room temperature, 4 g of a solution of acrylamidopropyl-trimethylammonium chloride (75% by mass in water), 3 g of distilled water, 4.5 g of ethanol, 750 mg of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 15 mg of V-50 initiator (2,2azobis(2-methyl-propionamidine)dihydrochloride) are introduced.

(51) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes.

(52) The flask was then placed in a thermostated oil bath at 60 C. and the medium was left with stirring at this temperature for 3 hours.

(53) At the end of the reaction, a 100% conversion was determined by .sup.1H NMR.

(54) A number molar mass M.sub.n=1,500 g/mol is calculated by .sup.1H NMR for the thereby prepared polymer P7.

7.2: Synthesis of the Diblock Copolymer

(55) The reaction mixture from step 7.1 was dried in vacuo and then taken up in ethanol and precipitated from diethylether. The obtained precipitate was dried in vacuo for 24 hours in order to remove the residual solvents, whereby the polymer P7 was obtained as a powder.

(56) 110 mg of this powder was introduced into a 15 mL Schlenk at room temperature, and then 1 g of N-vinylpyrrolidone, 2 g of distilled water and 40 mg of a tertbutyl hydroperoxide solution (70% by mass in water) were added.

(57) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes.

(58) Next, 40 mg of sodium sulfite were added in one go under an argon stream, the reaction was left with stirring for 24 hours at room temperature.

(59) At the end of the reaction, a 99% conversion was determined by .sup.1H NMR.

(60) By comparing the analysis by DOSY NMR of the polymer P7 and of the copolymer from the example, the diblock nature of the copolymer is confirmed by considering the difference in the diffusion coefficients (D in m.sup.2/s) between P7 and the final copolymer. For P7 D=204 m.sup.2/s while for the PAA-PVP diblock, D=63 m.sup.2/s. Further, the DOSY 2D map of both samples gives the possibility of viewing that P7 has totally reacted during the step for polymerization of NVP, in order to be incorporated into the PAPTAC-PVP diblock.

EXAMPLE 8

Synthesis According to the Invention of a poly(acrylamide)-b-poly(N-vinyl pyrrolidone)diblock CopolymerTertbutyl Hydroperoxide/Sodium Sulfite Pair

8.1: Synthesis of a Live poly(acrylamide)polymer with a Xanthate End (Polymer P7)

(61) 10 g of an acrylamide solution stabilized with copper (50% by mass in water), 5.2 g of ethanol, 1.2 g of O-ethyl-S-(1-methoxycarbonyl ethyl)xanthate of formula (CH.sub.3CH(CO.sub.2CH.sub.3))S(CS)OEt and 160 mg of a tertbutyl hydroperoxide solution (70% by mass in water) were introduced into a 25 mL flask at room temperature.

(62) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes. Next, 160 mg of sodium sulfite were added in one go under an argon stream. The reaction was left with stirring for 24 hours at room temperature.

(63) At the end of the reaction, an 85% conversion is determined by .sup.1H NMR.

(64) A number molar mass M.sub.n=1,200 g/mol is calculated by .sup.1H NMR for the thereby prepared polymer P8.

8.2: Synthesis of the Diblock Copolymer

(65) The reaction medium from step 8.1 was dried in vacuo and then taken up in ethanol and precipitated from diethyl ether. The obtained precipitate was dried in vacuo for 24 hours in order to remove the residual solvents, whereby the polymer P8 was obtained as a powder.

(66) 100 mg of this powder were introduced into a 15 mL Schlenk at room temperature, and then 1 g of N-vinylpyrrolidone, 2 g of distilled water and 40 mg of a tertbutyl hydroperoxide solution (70% by mass in water) were added.

(67) The reaction mixture was degassed with extra pure argon bubbling for 30 minutes. Next, 40 mg of sodium sulfite were added in a single go under an argon stream. The reaction was left with stirring for 24 hours at room temperature.

(68) At the end of the reaction, a 99% conversion was determined by .sup.1H NMR.

(69) By comparing the analysis by DOSY NMR of the polymer P8 and of the copolymer from the example, the diblock nature of the copolymer is confirmed by considering the difference in the diffusion coefficients (D in m.sup.2/s) between P8 and the final copolymer. For P8, D=185 m.sup.2/s while for the PAM-PVP diblock, D=63 m.sup.2/s. Further, the DOSY 2D map of both samples gives the possibility of viewing that P8 has totally reacted during the step for polymerization of NVP, in order to be incorporated into the PAM-PVP diblock.