Effect of Hydration in Corona Layer on Structural Change of Thermo-Responsive Polymer Micelles.

ABSTRACT: The effect of hydration in corona layer on temperature responsiveness of polymer micelles consisting of poly(N-vinyl pyrrolidone)-block-poly(n-octadecyl acrylate) (PVP-b-PODA) was investigated. Small-angle X-ray scattering and dynamic light scattering showed two-step shape change of PVP-b-PODA micelles around 45 and 65 °C with elevating temperature, although only one-step shape change was observed at 45 °C in cooling process. In the first step, shape of PVP-b-PODA micelles was changed from disk to ellipsoidal oblate at the melting temperature (T_m) of PODA, although similar micelles consisting of another amphiphilic block copolymers containing PODA simply changed from disk to sphere at the T_m with elevating temperature. PVP-b-PODA micelles changed to spherical shape above 65 °C. Two-dimensional (2D) ¹H-NMR showed the PVP chains were perfectly dehydrated above 65 °C. Therefore, it was suggested that the appearance of ellipsoidal shape between T_m of PODA and 65 °C was caused owing to shape memory effect of pseudo network of corona layer due to robust hydration of PVP chains.

SUBMITTER: Akino Y 

PROVIDER: S-EPMC6419195 | biostudies-literature | 2019 Feb

REPOSITORIES: biostudies-literature