N-Ester-substituted polyacrylamides with a tunable lower critical solution temperature (LCST): the N-ester-substitute dependent thermoresponse

A series of N-ester-substituted polyacrylamides containing different N-ester-substitutes including poly(N-acryloylglycine) (PNAG), poly(N-acryloylglycine methyl ester) (PNAGME), poly(N-acryloylglycine ethyl ester) (PNAGEE) and poly(N-acryloylglycine propyl ester) (PNAGPE) are prepared by RAFT polymerization. The controlled RAFT synthesis of the N-ester-substituted polyacrylamides is achieved at moderate monomer conversion using trithiocarbonate or dithiobenzoate as a RAFT agent. The solution property of the N-ester-substituted polyacrylamides is investigated, and the N-ester-substitute dependent solution property of polyacrylamides is found. That is, with the carbon number in the N-ester-substitutes gradually increasing from 0 to 3, the solution property of the N-ester-substituted polyacrylamides changes greatly. The parameters affecting the lower critical solution temperature (LCST) of PNAGME are investigated, and it is found that the CONHCH₂ moiety contributes mainly to the dehydration of PNAGME at temperatures above the LCST. The present study clarifies how the structure of the N-ester-substitutes affects the solution property of N-ester-substituted polyacrylamides.