Creating Poly(tetramethylene oxide) Glycol-Based Networks with Tunable Two-Way Shape Memory Effects via Temperature-Switched Netpoints

• Published in: Macromolecules 2017-07, Vol.50 (13), p.5155-5164
• Main Authors: Xie, Hui, Cheng, Chuan-Ying, Deng, Xiao-Ying, Fan, Cheng-Jie, Du, Lan, Yang, Ke-Ke, Wang, Yu-Zhong
• Format: Article
• Language: English
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.6b02773

Polymers with two-way shape memory effect (2W-SME) are of great potential in real applications due to the reversible nature. Though 2W-SME has been already realized in some semicrystalline networks by the crystallization-induced elongation (CIE) and melting-induced contraction (MIC), more adaptable 2W-SME systems are highly expected. In this work, to achieve tunable 2W-SME with different reversible deformation ranges, we designed a semicrystalline poly­(tetramethylene oxide) glycol (PTMEG) network with temperature-switched netpoints. This adaptable network was constructed by photo-cross-linking of the PTMEG-based copolymer containing amorphous poly­(d,l-lactide) (PDLLA) segments in main chain and photosensitive anthracene groups in side chain. The photo-cross-linking degrees of networks were adjusted by controlling irradiation time. Remarkably, 2W-SME in the current system was realized by the CIE and MIC of PTMEG segments for the first time. Here, along with the photo-cross-links, the low content of PDLLA served as a switchable netpoint which was controlled by high temperature (T high). Differential scanning calorimetry (DSC) analysis revealed that all the photo-cross-linked networks exhibited desirable crystallinity. Dynamic mechanical analysis (DMA) indicated that there were two distinct declines of storage modulus (E′) when temperature crossed T m,PTMEG and T g,PDLLA, which guided us to choose 45 and 70 °C as two specific T highs. 2W-SME was investigated by DMA under constant stress; in detail, the effects of applied stress, T high, and photo-cross-linking degree synergizing with the switchable netpoints structure on the characteristics of 2W-SME (εi, εNon‑CIE, εCIE, R act(σ), and R rec(σ)) have been disclosed.