A reactive graphene sheet in situ functionalized hyperbranched polyurethane for high performance shape memory material

Abstract

A new and facile route has been developed to prepare graphene oxide (GO) reinforced hyperbranched polyurethane (HPU) composites by in situ polymerization technique. To increase the reactivity of GO during in situ polymerization, the aliphatic hydroxyl groups are decorated on the surface of graphene sheets. The enhanced grafting was confirmed by Fourier-transform infrared spectra and high resolution transmission electron microscopy. The high grafting yield of 84% was obtained from thermogravimetric analysis after removing the non-attached HPU from the composites. The covalently bonded graphene sheets with hyperbranched polyurethane were homogeneously dispersed due to grafted HPU-assisted dispersion in the pure polymer matrix. In comparison with pure hyperbranched polyurethane, the highly flexible graphene-based shape memory polyurethane composite exhibited higher modulus and breaking stress, and exceptional elongation-at-break. The resulting composite exhibited 98% shape recovery, 93% shape retention, and enhanced thermal stability; thus, it would be a promising material for the fabrication of graphene-based actuating devices. Consequently, this simple protocol has great potential in the preparation of various high-performance polymer composites.