Zhou Jian, Cao Heqing, Chang Ruoxing, Shan Guorong, Bao Yongzhong, Pan Pengju
State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, 38 Zheda Road, Hangzhou 310027, P. R. China.
ACS Macro Lett. 2018 Feb 20;7(2):233-238. doi: 10.1021/acsmacrolett.7b00995. Epub 2018 Feb 2.
Design of the polymer networks with tunable mechanical properties and multishape memory effects (multi-SMEs) is highly desired in the engineering applications. Herein, we report on the stereocomplexed and homochiral polyurethane (PU) elastomers with tunable multi-SMEs by cross-linking the triblock prepolymers bearing the poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) enantiomeric segments. The homochiral PU is nearly amorphous, yet the stereocomplexed PU becomes highly crystalline due to the stereocomplexation of enantiomeric segments. Moreover, the two distinct thermal (glass, melting) transitions of PLLA (or PDLA) segments in PUs are integrated to realize the thermally induced triple- and quadruple-SMEs. Control over the enantiomeric segmental ratios allows the feasible manipulation of crystallizability, mechanical and thermal properties, and multi-SMEs of PUs.
在工程应用中，非常需要设计具有可调机械性能和多重形状记忆效应（multi-SMEs）的聚合物网络。在此，我们报道了通过交联带有聚（L-乳酸）（PLLA）和聚（D-乳酸）（PDLA）对映体链段的三嵌段预聚物而制备的具有可调multi-SMEs的立体复合和同手性聚氨酯（PU）弹性体。同手性PU几乎是无定形的，但由于对映体链段的立体复合作用，立体复合PU变得高度结晶。此外，PU中PLLA（或PDLA）链段的两个不同的热（玻璃化、熔化）转变被整合起来以实现热致三重和四重形状记忆效应。对对映体链段比例的控制使得对PU的结晶性、机械和热性能以及multi-SMEs进行可行的调控成为可能。
