Influence of Macromolecular Architecture on the Thermal Response Rate of Amphiphilic Copolymers, Based on Poly(N-isopropylacrylamide) and Poly(oxyethylene), in Water

The effect of poly(oxyethylene), PEO, on the thermal response rate of aqueous solutions of poly( N -isopropylacrylamide), PNIPAM, block and graft copolymers has been discussed. The PNIPAM- b -PEO/water system reveals thermoresponsive properties similar to the PNIPAM/water system. In PNIPAM- g -PEO/water solutions, however, PEO provides hydrophilic channels, facilitating the diffusion of water molecules through the collapsed polymer aggregate at temperatures above the demixing temperature of the aqueous copolymer solution. As a result, the thermal response of the aqueous PNIPAM- g -PEO system is significantly faster than in the case of either pure PNIPAM or PNIPAM- b -PEO, indicating the influence of the macromolecular architecture. An attempt has also been made to correlate the thermal response kinetics of the aqueous solutions of different copolymers with the miscibility of the polymer constituents, i.e., PEO and the thermoresponsive PNIPAM backbone, which can vitrify during phase separation.