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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(ɛ-caprolactone) dimethacrylate as crosslinker and n -butyl acrylate as comonomer was introduced. The influence of two structural parameters, the molecular weight of oligo(ɛ-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.
Lendlein et al. (2001) studied this question.