Aqueous solution behavior of p(N-isopropyl acrylamide) in the presence of water-soluble macromolecular species

We report here the polymerization of N-isopropyl acrylamide (NIPAM) via the reversible addition fragmentation chain transfer (RAFT) process. Two trithiocarbonates (S,S'-bis(alpha, alpha'-dimethyl-alphaalpha-acetic acid)-trithiocarbonate and 2-dodecylsulfanvithiocarbonylsulfanyl-2-methyl propionic acid) were used as the chain transfer agents in conjunction with 4.4'-azobis(4-cyanovaleric acid) and 2,2'azobis(2-methylpropionamidine) dihydrochloride as the initiating species. Poly(NIPAM) is a thermo-responsive polymer that has a sharp lower critical solution temperature (LCST). Herein, we investigated the aqueous solution behaviour of well defined p(NIPAM) prepared by the RAFT process as a function of molecular weight (degree of polymerization: 50, 100 and 200) and temperature. Furthermore, we examine the influence of varying concentrations of macromolecular species (neutral polyethylene glycol (M-n - 3400 g/mol) and ionic bovine serum albumin (Mn - 63000 g/mol)) on the LCST of p(NIPAM). The aqueous solution behaviour was assessed by spectrophotometry, dynamic light scattering and surface tensiometry. The macromolecular additives was found to have a significant effect on the coil to globular transition of the lower molecular weight p(NIPAM). (C) 2007 Elsevier Ltd. All rights reserved.