Combined effects of confinement size and chain-end tethering on the crystallization of poly(ε-caprolactone) chains in nanolamellae

Abstract

The crystallization behavior of poly(ε-caprolactone) (PCL) chains spatially confined in a lamellar microdomain structure (nanolamella) with the PCL layer thickness d of 15.0 nm (space confinement) was examined using synchrotron small-angle X-ray scattering (SR-SAXS), differential scanning calorimetry (DSC), and infra-red spectroscopy (IR). The PCL chains were covalently tethered to nanolamella interfaces at both chain-ends, either chain-end, or no chain-end (chain confinement) to bring an additional change in their molecular mobility. The individual effect of space confinement and chain confinement on the crystallization of PCL chains was elucidated by comparing this result with that of PCL chains confined in a smaller nanolamella (i.e., d = 10.9 nm) derived in our previous study and of bulk PCL homopolymers without any confinements. Though the crystallization rate depended significantly on the state of chain-end tethering for PCL chains confined in the nanolamella with d = 10.9 nm, it converged toward bulk PCL with the difference considerably reduced when confined in the nanolamella with d = 15.0 nm. The melting temperature and crystallinity showed similar results. We tried to convert chain confinement into space confinement on the basis of crystallization rates experimentally obtained to understand their combined effect on the crystallization.