How graphene oxide affects shape memory properties and strength of poly( l -lactide-co-ε-caprolactone)

Abstract

Poly( l -lactide-co-ε-caprolactone) is an environment-friendly shape memory polymer. Molecular dynamics method was used to study the shape memory effect and mechanical properties of graphene oxide–reinforced poly( l -lactide-co-ε-caprolactone) to understand the microscopic mechanism. Two models containing dispersed graphene oxide were constructed. It is shown that the addition of graphene oxide causes the glass transition temperature of material to rise because of limitation on polymer activity. The uniaxial tensile properties of the composites were studied. The results exhibited that strength of composites depend on the interface state of the polymer and graphene oxide. The strength of the composite with covalent bond is much higher than that of another without the covalent bond between graphene oxide and poly( l -lactide-co-ε-caprolactone) generated. Stress softening effect was observed in the cross-linked composite in the glass state. Their uniaxial tension thermodynamic cycles were carried out to consider the shape memory effect of the composites. It is shown that graphene oxide–reinforced composites with different interactions exhibit fair shape memory effect in the direction of paralleling graphene oxide surface. In terms of the direction perpendicular to graphene oxide sheet, the fixed ratios of the composites decrease slightly about 1.64%–3.63%, and the recovery ratios of the composites with the covalent bond are higher than others about 3.22%–12.93%.