Polymer hydration and microphase decomposition in poly(N-vinylcaprolactam)-water complex

• Published in: Journal of applied crystallography 2003-08, Vol.36 (4), p.967-969
• Main Authors: Lebedev, Vassili, Török, Gyula, Cser, László, Treimer, Wolfgang, Orlova, Diana, Sibilev, Avgustin
• Format: Article
• Language: English
• Subjects: collapse; phase transition; polymer
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S0021889803008422

Poly(N‐vinylcaprolactam) (PVCL) is a synthetic analogue of biomolecules (enzymes, proteins). It demonstrates a specific hydration and undergoes a coil–globule 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).