Thermally Sensitive and Biocompatible Poly(N-vinylcaprolactam): Synthesis and Characterization of High Molar Mass Linear Chains

High molar mass poly(N-vinylcaprolactam) (PVCa) was synthesized by free-radical bulk polymerization. Four narrowly distributed fractions of PVCa were obtained in the tetrahydrofuran/nhexane mixture. A combination of static and dynamic laser light scattering led to a scaling between the translational diffusion coefficient (D) and molar mass (M), D (cm2/s) ) 8.47 × 10Mw, with which we transferred the translational diffusion coefficient distribution of each fraction into a corresponding molar mass distribution. We also established a scaling between the weight average molar mass (Mw) and the radius of gyration (〈Rg〉), 〈Rg〉 (nm) ) 2.94 × 10Mw, for PVCa in water at 25 °C. Moreover, we found a novel way to estimate the Θ-temperature (∼29.5 °C) from the temperature and concentration dependence of the hydrodynamic radius (〈Rh〉). The lower critical solution temperature (LCST, ∼31.5 °C) of linear PVCa chains in water determined from the variations of both 〈Rh〉 and scattering intensity is close to the shrinking temperature of the PVCa hydrogel.