Influence of the addition of water to amorphous switching domains on the simulated shape-memory properties of poly(L-lactide)

POLYMER

卷:54

Article

Ghobadi, E.¹  Heuchel, M.¹  Kratz, K.¹  Lendlein, A.¹ 

[1] Helmholtz Zentrum Geesthacht, Inst Biomat Sci, D-14513 Teltow, Germany

关键词: Molecular dynamics simulation;    Shape-memory polymers;    Poly(L-lactide);   

DOI  :  10.1016/j.polymer.2013.05.064

来源: Elsevier

【 摘 要 】

It is well known that the environmental conditions e.g. humidity can alter the shape-memory properties of polymers. In this work we applied an atomistic molecular dynamics simulation approach to model the influence of the addition of 1 wt% and 2 wt% water on the simulated shape-memory behavior of the amorphous switching domains of poly(L-lactide) (PLLA) with a molecular weight of M-n = 52,000 g mol(-1). For the dry as well as the water swollen PLLA-models, two subsequent uniaxial thermomechanical test cycles have been calculated, whereby the applied uniaxial deformation epsilon(m) was varied between 50% and 150%. All simulated PLLA models showed high shape fixity ratio of R-f >= 84%. The shape-memory properties obtained at epsilon(m) = 100% for the dry PLLA and the models containing 1 wt% water were almost identical with a shape recovery ratio in the first and second test cycle around R-r = 61%-64%. In contrast PLLA with 2 wt% water exhibited higher values of R-r = 76% during the first test cycle, but a lower R-r = 52% in the subsequent second cycle. Furthermore, increasing the applied epsilon(m) resulted in a decrease of R-r from 82% to 42% for the dry PLLA, whereas PLLA with 2 wt% water did not show a dependence of R-r on epsilon(m). We anticipate that these observations can be attributed to differences in the initial structure of the various simulated PLLA models e.g. the different distribution of the free volume elements. (C) 2013 Elsevier Ltd. All rights reserved.

【 授权许可】

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