Effect of hard segment architecture on shape memory properties of polycaprolactone-based polyurethane containing azobenzene
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In this work, we synthesized two kinds of polyurethanes with azobenzene as hard segments in the side chains and in the main chains. Their thermal stabilities were high enough for their shape memory application. For polyurethane with azobenzene in the side chain (PU), the azobenzene has more distinctly effect on inhibiting crystallization of polycaprolactone (PCL) because of irregular orientation of azobenzene. For polyurethane with azobenzene in the main chain (PUR), the crystallinity of PCL is mainly affected by its molecular weight. PU-3500 and PUR-3500 exhibit perfect shape fixing ability of 99 % with recovery ratio of 98 % at 50 % strain. The recovery ratio is decreased for PU-3500 and increased for PUR-3500 as the applied strain increased. The mechanism of the hard segment structures effect on the shape memory behavior is briefly discussed. Importantly, the two molecules behave trans–cis isomerization under UV irradiation. This work is crucially important for the structural design of shape memory polyurethane and applications in the smart devices.
KeywordsShape Memory Dynamic Mechanical Analysis Azobenzene Shape Memory Effect Hard Segment
The financial supported by Program for Scientific Research Innovation Team in Colleges and Universities of Shandong Province, the National Natural Science Foundation of China (21204044, 21176147), the Natural Science Foundation of Shandong Province for Excellent Young Scholars (ZR2015JL009) and Ji’nan Overseas Students Pioneer Plan (20120202) are gratefully acknowledged.
Supplementary material 2 (MPG 4539 kb)
Supplementary material 3 (MPG 4430 kb)
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