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.
Photo‐iniferter reversible addition‐fragmentation chain transfer (PI‐RAFT) polymerization of N‐vinylformamide (NVF) is demonstrated by using purple light. PNVFs with predetermined molar masses and narrow molar mass distributions are obtained. High RAFT chain‐end fidelity is confirmed by matrix‐assisted laser desorption ionization time‐of‐flight (MALDI‐TOF) and electrospray‐ionization time‐of‐flight mass spectrometry (ESI‐TOF‐MS), and chain extension experiment. To demonstrate the potential of this approach, an original poly(N‐vinylpyrrolidone)‐b‐poly(N‐vinylformamide) (PVP‐b‐PNVF) diblock copolymer is synthesized and characterized by aqueous size‐exclusion chromatography (SEC), asymmetric flow field‐flow fractionation (A4F), and 1H diffusion‐ordered spectroscopy nuclear magnetic resonance (1H DOSY NMR). Finally, selective hydrolysis of PNVF block to corresponding pH‐responsive poly(N‐vinylpyrrolidone)‐b‐poly(N‐vinylformamide) (PVP‐b‐PVAm) is performed.
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