Lendlein A, Schmidt A M, Langer R
Institute for Technical and Macromolecular Chemistry, Rheinisch Westfälische Technische Hochschule (RWTH) Aachen, Germany.
Proc Natl Acad Sci U S A. 2001 Jan 30;98(3):842-7. doi: 10.1073/pnas.98.3.842. Epub 2001 Jan 23.
Although shape-memory metal alloys have wide use in medicine and other areas, improved properties, particularly easy shaping, high shape stability, and adjustable transition temperature, are realizable only by polymer systems. In this paper, a polymer system of shape-memory polymer networks based on oligo(epsilon-caprolactone) dimethacrylate as crosslinker and n-butyl acrylate as comonomer was introduced. The influence of two structural parameters, the molecular weight of oligo(epsilon-caprolactone) dimethacrylate and the weight content of n-butyl acrylate, on macroscopic properties of polymer networks such as thermal and mechanical properties has been investigated. Tensile tests above and below melting temperature showed a decrease in the elastic modulus with increasing comonomer weight content. The crystallization behavior of the new materials has been investigated, and key parameters for the programming procedure of the temporary shape have been evaluated. Shape-memory properties have been quantified by thermocyclic experiments. All samples reached uniform deformation properties with recovery rates above 99% after 3 cycles. Whereas strain recovery increased with increasing n-butyl acrylate content, strain fixity decreased, reflecting the decreasing degree of crystallinity of the material.
尽管形状记忆金属合金在医学和其他领域有广泛应用，但只有聚合物体系才能实现性能的改善，特别是易于成型、高形状稳定性和可调节的转变温度。本文介绍了一种基于低聚（ε-己内酯）二甲基丙烯酸酯作为交联剂和丙烯酸正丁酯作为共聚单体的形状记忆聚合物网络的聚合物体系。研究了两个结构参数，即低聚（ε-己内酯）二甲基丙烯酸酯的分子量和丙烯酸正丁酯的重量含量，对聚合物网络宏观性能（如热性能和机械性能）的影响。在熔点温度上下进行的拉伸试验表明，随着共聚单体重量含量的增加，弹性模量降低。研究了新材料的结晶行为，并评估了临时形状编程过程的关键参数。通过热循环实验对形状记忆性能进行了量化。所有样品在3个循环后均达到均匀的变形性能，回复率高于99%。随着丙烯酸正丁酯含量的增加，应变回复增加，而应变固定率降低，这反映了材料结晶度的降低。
