Influence of free PCL in PCL/PBA-a copolymers and blends on morphology, thermo-mechanical and shape memory properties

Abstract Poly( e -caprolactone) (PCL) and bisphenol A based polybenzoxazine (PBA-a) blends and copolymers differing in the amount of PCL and bonding mode are reported aiming at studying the role of free PCL. Copolymers containing and lacking free PCL were used to understand the influence of PCLs bonding mode on morphology and mechanical properties. XRD and DSC studies revealed that free PCL in the samples increased the degree of crystallinity in contrast to samples containing similar but bound amounts of PCL. Free PCL tends to phase separate leading to discontinuous phases in the appropriate blends in contrast to smooth surfaces and homogeneous copolymer-like samples as confirmed by AFM and SEM micrographs. Reduced crystallinity due to the absence of free PCL results in a less stabilized network and thereby in a diminished material stiffness. In view of shape memory properties, this study revealed that both a widened network due to covalent PCL incorporation and the existence of free and motile PCL facilitating crystallization are important parameters for the occurrence of shape memory abilities in PCL/PBA-a copolymers.