Shape-memory behavior of cross-linked semi-crystalline polymers and their blends

Abstract

The aim of present mini-review is an attempt to perform the comparative description and analysis of results of our experimental investigation and of physically justified modeling of unconstrained one-way shape-memory effect (SME) and invertible twoway SME under load in crystallizable covalent polymer networks. Besides the dual SME in cross-linked homopolymers, the one-and two-way multi-shape behavior in heterogeneous networks on the basis of binary and ternary blends will be discussed. The special focus in present work is directed on the key role of phase morphology of cross-linked polymer blends varied by blend composition on the performances of multiple SM behavior. Brief overview of various types of SME in polymeric materialsIn the last decades the SME in polymeric materials was the research object of hundreds of original papers and many reviews (see for instance [1][2][3][4][5][6][7][8]). There are four main types of stimuli, which are able to trigger a shape change of polymeric materials: temperature variation, chemical reactions, light, and mechanical forces [2][3][4][5][6][7]. Correspondingly, among polymeric materials the thermo-, chemo-, photo-, and mechano-responsive material groups can be classified. In majority of publications, which consider SM behavior of polymer systems, the subject of investigation are thermo-responsive polymeric materials. According to the existence of ordered Abstract. The present study deals with thermally induced one-way and invertible two-way shape-memory effect (SME) in covalent networks on the basis of crystallizable (co)polymers and their blends and is an attempt to generalize the results of own investigation received by the authors in the last ten years. The main focus of work clearly lies on research of covalently crosslinked binary and ternary blends having two and three crystalline phases with different thermal stability, respectively. The existence of two or three crystalline phases possessing different melting and crystallization temperatures in heterogeneous polymer networks can lead to triple-shape or even quadruple-shape behavior of such networks. However, the performed investigations point to crucial effect of phase morphology of crosslinked polymer blends on multiplicity of their shapememory behavior beside the influence of blend content, crystallinity and cross-link density of blend phases as well as of processing conditions. For instance, triple-shape memory behavior in binary blends can be realized only if the continuous phase has a lower melting temperature than the dispersed phase. Cross-linked polymer blends are a facile alternative to expensive and complex synthesis of interpenetrating or block-copolymer networks used for shape memory polymers. In addition to findings of experimental investigation of SME in crystallizable covalent polymer networks, the results of modeling their shape-memory behavior on the basis of self-developed physically reasonable model have been briefly described and discussed. Thereby, good accordance between results of theory and ...

A Facile Strategy to Fabricate Multishape Memory Polymers with Controllable Mechanical Properties

“…Polymer blending strategy, which usually combines transition component to respond to stimulus and network‐forming component to restore permanent shape, is a facile and widely used strategy to prepare conventional dual‐SMPs . However, little works have fabricated multi‐SMPs with satisfactory shape memory properties by blending approach.…”

Development of zwitterionic copolymers with multi-shape memory effects and moisture-sensitive shape memory effects

“…[21][22][23] SMPs with multi-SME, called as multi-SMPs, are believed to have significant and broad technology impacts. 1 For instance, triple-memory properties could be achieved by designing two thermal transitions in multi-block segmented polyurethanes, [24][25][26] grafting polymers, 27,28 semi-interpenetrating polymer networks, 29 polymer blends, 30,31 or polymer composites. [21][22][23] One strategy is to incorporate several discrete thermal transitions into the material.…”

Multiple shape memory effects of trans‐1,4‐polyisoprene and low‐density polyethylene blends

“…The second part can be easily deformed to maintain a temporary shape and is often a crystalline portion or soft segments of a polymer; it is called the reversible domain. The transition temperature ( T trans ) is vital for the shape memory mechanism of thermally induced SMPs, which can be the glass transition temperature ( T g ) for amorphous polymers or the melting temperature ( T m ) for crystalline polymers . SMPs have been shown to be deformed by an applied external force above T trans and to have their temporary shapes fixed by cooling below T trans , induced by the molecular mobility of the reversible domain in SMPs.…”

“…SMPs have been shown to be deformed by an applied external force above T trans and to have their temporary shapes fixed by cooling below T trans , induced by the molecular mobility of the reversible domain in SMPs. When the temperature is again elevated above T trans , the SMPs contract to their original shape due to the entropic elasticity of the molecular chains, usually referred to as the one‐way shape memory effect (SME) …”