Shape memory properties of electrically conductive multi-walled carbon nanotube-filled polyurethane/modified polystyrene blends

Abstract

Shape memory polyurethanes are synthetic materials with great potential to respond to external stimulus. Desired properties of shape memory polyurethanes can be achieved by blending with other polymers or varying the hard and soft segments. In this study, structure, morphology, mechanical, thermal and electrical conductivity properties of a shape memory blend reinforced with multi-walled carbon nanotube were investigated. One blend component was polyethylene glycol and toluene diisocyanate polyurethane, and the second component was either polystyrene or nitro-functional or amino-functional. The fundamental chemical and physical linkages were confirmed by Fourier transform infrared spectroscopy. Field emission scanning electron microscopic images demonstrated the generation of polyurethane–polystyrene interpenetrating polymer network over multi-walled carbon nanotube surface. The tensile strength and modulus were found to increase systematically with increasing filler content in all series and was higher for polyurethane/polystyrene amino-functional/multi-walled carbon nanotube composites. The stress-bearing capacity and mechanical properties were enhanced due to a matrix made up of two different chemically interlinked polymers. On the whole, using amino-functional polystyrene showed better physical and shape memory properties. Electrical conductivity was superior for composites with polystyrene amino-functional matrix, compared with neat blend and other composite. The polyurethane/polystyrene amino-functional/multi-walled carbon nanotube 0.5 electrical conductivity tested at 1.08 S cm⁻¹. The polyurethane/polystyrene amino-functional/multi-walled carbon nanotube composites showed remarkable thermally triggered shape memory behavior to the extent of 95%. Electric field-triggered shape recovery of the polyurethane/polystyrene amino-functional/multi-walled carbon nanotube sample was found to be 96%. The synergetic effect of the fine electrical conductivity and high mechanical strength renders the composites as high-performance shape memory materials.