Water-soluble poly (n-vinylamidess): Microstructure, solvation, conformational state and complex formation in aqueous solutions

Energetics of Cooperative Transitions of N‐Vinylcaprolactam Polymers in Aqueous Solutions

“…[8] Aqueous solutions of this polymer are demixed upon heating. The phase diagram has the critical point at a temperature of ca.…”

Approaches to Chemical Synthesis of Protein-Like Copolymers

“…The turbidity of the systems increases sharply after certain threshold temperatures. This indicates the temperature-dependent phase separation typical for LCST-exhibiting polymers such as the NVClhomopolymers [28][29][30][31]. At the same time, the s-fractions of poly(NVCl-coNVIAz) either did not precipitate from the aqueous solutions at all till 70 • C, or the LCST effects were observed at temperatures considerably higher (by 20-30 • C) than for the corresponding p-fractions.…”

“…In turn, the fractions had significant differences in molecular weights and, importantly, exhibited absolutely different temperature-dependent solution behaviour. The fraction p began to precipitate at 34 • C (in fact, similar to the NVCl-homopolymers [28][29][30][31]), and the s-fraction remained water-soluble at least up to 70 • C. The latter fraction, as well as the s-fraction of copolymer obtained from the feed with an initial comonomer molar ratio of 90 : 10, are both marked in grey in Table 1 because they were identified to possess a protein-like structure in aqueous media at definite temperatures.…”

“…Such a length is too short to cause pronounced heatinduced phase separation effects typical for the thermoresponsive NVClcopolymers. However, the phase transition for such thermally precipitating fractions started at the temperatures 33-44 • C, i.e., in the region of T cp values characteristic of the NVCl-homopolymers (32-45 • C, depending on the polymer molecular weight [28,30,31,33,34]). Therefore, it can be assumed that all the NVCl/NVIAz-copolymers of the o-and p-types were not the random copolymers with the short oligoNVCl segments.…”

“…4b). Inasmuch as the conformational transition of the chains of thermoresponsive polymers in an aqueous medium is accompanied by a collapse of such macromolecules [31,41], such a collapse has to result in a decrease in mobility of bound water and, thereby, in a broadening of the whole width of the NMR signal from the water protons. This was observed for the s-copolymer as an increase in the ∆ 1/2 ν parameter from 37 to 39 • C. It indicates a compaction of the structure of these macromolecules at the temperatures, where the transition effect was registered by the HS-DSC, but no macroscopic phase separation took place.…”