Issue 20, 2012
From the journal:

Soft Matter

Mechanisms of multi-shape memory effects and associated energy release in shape memory polymers

Kai Yu,a   Tao Xie,b   Jinsong Leng,c   Yifu Dinga  and  H. Jerry Qi*a  

* Corresponding authors

a Department of Mechanical Engineering, University of Colorado, UCB 427, Boulder, CO 80309, USA
E-mail: qih@colorado.edu

b Chemical Sciences and Materials Systems Laboratory, General Motors Research and Development Center, Mail Code: 480-106-224, 30500 Mound Road, Warren, Michigan 48090-9055, USA

c Centre for Composite Materials, Science Park of Harbin Institute of Technology (HIT), P.O. Box 3011, No. 2 YiKuang Street, Harbin, P.R. China

Abstract

Shape memory polymers have attracted increasing research interest due to their capability of fixing a temporary shape and associated deformation energy then releasing them later on demand. Recently, it has been reported that polymers with a broad thermomechanical transition temperature range can demonstrate a multi-shape memory effect (m-SME), where shape recovery and energy release occur in a stepped manner during free recovery. This paper investigated the underlying physical mechanisms for these observed shape memory behaviors and the associated energy storage and release by using a theoretical modeling approach. A multibranch model, which is similar to the generalized standard linear solid model of viscoelasticity, was used for a quantitative analysis. In this model, individual nonequilibrium branches represent different relaxation modes of polymer chains with different relaxation times. As the temperature was increased in a staged manner, for a given temperature, different numbers of branches (or relaxation modes) became shape memory active or inactive, leading to the observed m-SME. For energy release during free recovery, under a tensile deformation of the SMP, stored energy in individual nonequilibrium branches was first transferred into a compressive deformation energy, then gradually declined to zero. Energy release during recovery was a complicated process due to the involvement of multiple relaxation modes.

Graphical abstract: Mechanisms of multi-shape memory effects and associated energy release in shape memory polymers

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Article information

DOI
https://doi.org/10.1039/C2SM25292A
Article type
Paper
Submitted
09 Feb 2012
Accepted
19 Mar 2012
First published
17 Apr 2012

Soft Matter, 2012,8, 5687-5695

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Mechanisms of multi-shape memory effects and associated energy release in shape memory polymers

K. Yu, T. Xie, J. Leng, Y. Ding and H. J. Qi, Soft Matter, 2012, 8, 5687 DOI: 10.1039/C2SM25292A

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