Association in Aqueous Solutions of a Thermoresponsive PVCL-g-C11EO42 Copolymer

Thermoresponsive associations in aqueous solution of poly(N-vinylcaprolactam) chains grafted with ω-methoxy poly(ethylene oxide) undecyl α-methacrylate (PVCL-g-C11EO42) at different copolymer concentrations have been investigated with the aid of various experimental methods. Turbidity measurements reveal that the cloud point (CP) decreases with increasing polymer concentration, and this effect is more pronounced in the semidilute concentration regime. Small-angle neutron scattering (SANS) results at large scattering wavevectors suggest a gradual conformational transition from random coils to contracted coils in the dilute concentration regime as the temperature rises. The rheological experiments disclose a strong temperature-induced contraction of the molecules in the dilute concentration regime, and the results in the semidilute regime indicate that the polymer chains are unentangled even at high concentrations. Dynamic light scattering results on solutions at temperatures up to the CP show the existence...