Facile fabrication of ternary nanocomposites with selective dispersion of multi-walled carbon nanotubes to access multi-stimuli-responsive shape-memory effects

Abstract

How to realize the multi-stimuli-response of shape-memory polymers in a simple system is a big challenge for researchers. In this study, a facile approach to produce a series of ternary nanocomposites made of a poly(butylene succinate)–poly(ε-caprolactone) (PBSPCL) multiblock copolymer matrix and multi-walled carbon nanotubes (MWCNTs) is described. MWCNTs were easily introduced into the double-crystalline copolymer matrix using solution mixing and solvent casting processes, successively. As a consequence of the immiscibility between these two polymeric segments, the spontaneous selective dispersion of MWCNTs is realized in the matrix with refined microphase separation morphology. The different affinity of MWCNTs for the PBS or PCL segment drove the MWCNTs to be localized in the PBS domain preferentially, as demonstrated by TEM analysis. This elaborate design leads to a significant reduction of percolation thresholds with the optimized composition of the nanocomposites. Moreover, the selective dispersion of MWCNTs in the hard PBS segment improved the strength of the material without deteriorating its ductility. Dynamic thermomechanical tests revealed that the PBSPCL copolymers exhibit an excellent dual-shape memory effect, as attested by the fix ratio (R_f) and recovery ratio (R_r) of 98%. After incorporation of MWCNTs into the matrix, the electro- and NIR-induced shape-memory effects have been realized, and the sample containing 40% PBS segment and 1 wt% MWCNTs exhibits optimal structure and performance.