RAFT polymerization of N-vinylcaprolactam and effects of the end group on the thermal response of poly(N-vinylcaprolactam)

The reversible addition-fragmentation chain transfer (RAFT) radical polymerization of N-vinylcaprolactam (NVCL) was performed using either S-benzyl-S-(benzyl propionate) trithiocarbonate (CTA 1) or N, N-diethyl-S-(α,α′- dimethyl-α″-acetic acid) dithiocarbamate (CTA 2) as a chain transfer agent (CTA). The polymerizations were controlled processes that yielded polymers with high conversion (>60%), controlled molecular weights that were close to the theoretical values and a narrow molecular weight distribution (minimal value: 1.13). The cloud point temperatures of poly(N-vinylcaprolactam) (PNVCL) were measured by turbidimetry and shifted to lower temperature and concentrations as the hydrophobicity of the end groups and the molecular weights of the polymers increased.