RAFT Polymerization of N-Methyl-N-vinylacetamide and Related Double Hydrophilic Block Copolymers

Abstract

Bulk reversible addition−fragmentation chain-transfer polymerization (RAFT) of N-methyl-N-vinylacetamide (NMVA) was explored with four different RAFT agents, which are two xanthates and two dithiocarbamates. Working at 35 °C with an unusually high [V-70] 0 /[RAFT agent] 0 ratio, cyanomethyl O-ethyl carbonodithioate and cyanomethyl diphenylcarbamodithioate allowed the synthesis of poly(N-methyl-N-vinyl acetamide) (PNMVA) with predetermined M n and relatively low dispersities (Đ < 1.5). A good thiocarbonylthio end-group fidelity was revealed by 1 H nuclear magnetic resonance (NMR), mass spectrometry, chain-extension experiment, and block copolymer synthesis. Two double hydrophilic poly(ethylene oxide)-b-poly(N-methyl-N-vinylacetamide) (PEO-b-PNMVA) and poly(N-isopropylacrylamide)-bpoly(N-methyl-N-vinylacetamide) (PNIPAAm-b-PNMVA) diblock copolymers were successfully synthesized, the latter of which exhibits a lower critical solution temperature (LCST) with the reversible formation of colloidal aggregates in water.

RAFT polymerisation of N-vinylformamide and the corresponding double hydrophilic block copolymers

“…This result was relatively unexpected when considering that these reaction conditions correspond to an initiator to the CTA1 ratio of 0.83, which is way higher than for classical RAFT conditions. A similar phenomenon was encountered in a recent study by our group on the RAFT polymerisation of NMVA, 40 where polymerizations showed an unexpectedly good level of the control of molar masses for an abnormally high [V-70]/ [CTA] ratio of 1.49/1. This result may be ascribed to the low efficiency of V-70 in NVF polymerization.…”

“…1), a common phenomenon in RAFT polymerisation of N-vinylamides with xanthate CTAs. 40 These three concentrations correspond to the [V-70] 0 / [CTA1] 0 ratios of 0.83, 0.33 and 0.10, respectively. While the highest conversion (93%) was obtained with [V-70] 0 /[CTA1] 0 = 0.83, the important amount of the initiator relative to CTA1 used could decrease the quality of the control by generating a high proportion of dead chains.…”

“…The choice of low temperature conditions was driven by the fact that xanthate terminal end groups of poly(N-vinylamides) are often thermally unstable, as exemplified in the literature 50 and also more recently by our group. 36,37,40 DMSO was selected as a suitable low transferring organic solvent able to solubilize PNVF.…”

“…Reversible addition–fragmentation chain transfer (RAFT) polymerisation is a user-friendly RDRP technique applicable to a wide range of monomers 31–33 including cyclic N -vinylamides such as N -vinylpyrrolidone (VP), 34–37 N -vinylcaprolactam (VCL), 35,38 and N -vinylpiperidone (VPI) 39 and recently to the non-cyclic N -methyl- N -vinylacetamide (NMVA). 40…”

“…Reversible addition-fragmentation chain transfer (RAFT) polymerisation is a user-friendly RDRP technique applicable to a wide range of monomers [31][32][33] including cyclic N-vinylamides such as N-vinylpyrrolidone (VP), [34][35][36][37] N-vinylcaprolactam (VCL), 35,38 and N-vinylpiperidone (VPI) 39 and recently to the non-cyclic N-methyl-N-vinylacetamide (NMVA). 40 In contrast, reports on RAFT polymerisation of NVF are scarce. Beckman and coworkers described the synthesis of poly(ethylene oxide)-b-poly(N-vinylformamide) (PEO-b-PNVF) block copolymers using a xanthate-terminated PEO as a macro-RAFT agent.…”