The effects of PCL diol molecular weight on properties of shape memory poly(ε-caprolactone) networks

Shape memory poly(epsilon-caprolactone) (PCL) networks with different molecular weights of PCL diol were prepared via thiol-ene reaction in this work. The highly efficient thiol-ene reaction ensured a uniform distribution of PCL chains between crosslinker, contributing well-defined network architecture with good mechanical and shape memory properties. H-1 NMR spectra were used to confirm that PCL diol was completely converted into acrylate-terminated PCL. Gel content experiment and Fourier-transform infrared showed that almost all samples exhibited virtually the complete crosslinking network due to the highly selective thiol-ene reaction between acrylate-terminated PCL and tetrathiol crosslinker. Differential scanning calorimetry and X-ray diffraction tests revealed that the melting temperature and crystallinity of the prepared PCL networks by using high molecular weight of PCL diol displayed a higher result compared to ones using low molecular weight. The dynamic mechanical analyzer results revealed that the storage modulus of the network dropped evidently across the thermal transition, these characteristics of the PCL network indicated that all exhibited a good shape memory effect. The shape fixing ability was kind of being affected by the PCL diol molecular weight, while the shape recovery ratio of all samples can almost reach 99% irrespective of the length of PCL diol. (c) 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47055.