Relation between temperature memory effect and multiple-shape memory behaviors based on polymer networks

Abstract

The temperature memory effect (TME) refers to the capability of shape memory materials to memorize the deformation temperature (T_d). In this article, the TME of multiple-shape memory polymer based on a PMMA/PEG semi-interpenetrating polymer network (PMMA/PEG semi-IPN) and a PMMA-PCL covalently crosslinked polymer co-network (PMMA-PCL CPN) are studied, and the relation between the TME and the multiple-shape memory effect (SME) is investigated. The results indicate that both the PMMA/PEG semi-IPN and PMMA-PCL CPN can show the TME in a specific range of response temperatures but not in its entire range of glass transition temperatures (T_g). This paper further confirms that broad transition temperature is the key to realizing the TME and the multiple-SME. Furthermore, we discover that the characteristic temperature of the TME corresponds to the multi-step transition temperature of the multiple-SME for the first time. Consequently, the characteristic temperature of the TME can be directly used as a multi-gradient T_d to achieve the multiple-SME. Thus it facilitates the selection of a multi-gradient T_d in the multiple-SME. The paper also reveals the internal relation of broad T_g, TME and multiple-SME of PMMA/PEG semi-IPN and PMMA-PCL CPN.