Mechanical and shape-memory properties of poly(mannitol sebacate)/cellulose nanocrystal nanocomposites

Abstract

Polyesters based on polyols and sebacic acid, known as poly(polyol sebacate)s (PPS), are attracting considerable attention, as their properties are potentially useful in the context of soft-tissue engineering applications. To overcome the drawback that PPSs generally display rather low strength and stiffness, we have pursued the preparation of nanocomposites based poly(mannitol sebacate) (PMS), a prominent example of this materials family, with cellulose nanocrystals (CNCs). Nanocomposites were achieved in a two-step process. A soluble, low-molecular-weight PMS pre-polymer was formed via the polycondensation reaction between sebacic acid and D-mannitol. Nanocomposites with different CNC content were prepared by solution-casting and curing under vacuum using two different profiles designed to prepare materials with low and high degree of crosslinking. The as-prepared nanocomposites have higher stiffness and toughness than the neat PMS matrix while maintaining a high elongation at break. A highly crosslinked nanocomposite with a CNC content of 5 wt % displays a sixfold increase in Young’s modulus and a fivefold improvement in toughness. Nanocomposites also exhibit a shape memory effect with a switch temperature in the range of 15 to 45 C; in particular the materials with a thermal transition in the upper part of this range are potentially useful for biomedical applications