Poly(N-vinylcaprolactam) (PVCL) is a synthetic analogue of biomolecules (enzymes, proteins). It demonstrates a specific hydration and undergoes a coilglobule transition. The PVCL-D2O system (PVCL mass M = 106) has been investigated by small-angle neutron scattering (SANS) at T = 296-316 K to identify the structural features of the collapse at concentration C = 0.5 wt% near the threshold of the coil overlap. (The collapse leads to the segregation of the phase enriched with polymer at T > 305 K). The SANS experiments at q = 0.1-5 nm-1 (scales from monomer unit to globule gyration radius RG ≃ 16 nm) have revealed a stretched coil-globule transformation in the range 305-309 K. Using high-resolution SANS (q = 0.002-0.02 nm-1) the globule association to form fractal structures (sponge-like) of surface dimension DF ≃ 2.4-2.6 was examined. The coexistence of globules and disordered chains (regions ∼5-10 nm) was found. The growth of the content of globular phase was induced by the conformational transition in disordered molecular fragments from coiled (dimension D ≃ 1.8) to stretched chains (D ≃ 1.2).
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)