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

• Published in: Polymers Vol. 11; no. 2; p. 382
• Main Authors: Akino, Yusuke, Morimoto, Kosuke, Tsuboi, Kengo, Kanazawa, Satoshi, Akiba, Isamu
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 22.02.2019; MDPI
• Subjects: Aqueous solutions; Block copolymers; Cooling; Crystallization; Dehydration; Hydration; Melt temperature; Micelles; Molecular weight; NMR; Nuclear magnetic resonance; Phase transitions; Photon correlation spectroscopy; polymer micelle; Polymerization; Polymers; Shape effects; Shape memory; small-angle X-ray scattering; Spectrum analysis; temperature responsiveness; X-ray scattering; Japan; polymer micelle; small-angle X-ray scattering; temperature responsiveness; hydration
• ISSN: 2073-4360; 2073-4360
• DOI: 10.3390/POLYM11020382

The effect of hydration in corona layer on temperature responsiveness of polymer micelles consisting of poly( -vinyl pyrrolidone)- -poly( -octadecyl acrylate) (PVP- -PODA) was investigated. Small-angle X-ray scattering and dynamic light scattering showed two-step shape change of PVP- -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- -PODA micelles was changed from disk to ellipsoidal oblate at the melting temperature ( ) of PODA, although similar micelles consisting of another amphiphilic block copolymers containing PODA simply changed from disk to sphere at the with elevating temperature. PVP- -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 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.