Free Volume Study on Three Types of Shape Memory Polymers by Positron Annihilation
Y. Ujihira, H.-L. Li and K. Ito
Research Center for Advanced Science and Technology, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904, Japan
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Temperature dependence of nanoscopic environment of shape memory polymers such as polynorbornene (Tg≈313 K), polyurethane (Tg≈321 K=dynamic viscoelasticity, destruction of hydrogen bond ≈353 K) and styrene-butadiene copolymer (Tm=333 K) is observed in terms of free volume parameters - average size, numerical concentration and size distribution - estimated from positronium lifetime measurement, and mechanisms of their shape recoveries are discussed at a molecular level.
DOI: 10.12693/APhysPolA.95.677
PACS numbers: 64.70.Pf