Crystallization behavior of poly(ε-caprolactone) chains confined in lamellar nanodomains

The crystallization behavior of poly(ε-caprolactone) (PCL) homopolymers and PCL blocks confined in identical lamellar nanodomains (L-domains) has been examined using differential scanning calorimetry and synchrotron small-angle X-ray scattering as a function of PCL layer thickness d and crystallization temperature. The PCL homopolymers confined in the L-domains with d = 8.7 nm (small L-domain) and 15.8 nm (large L-domain) were prepared using microphase separation of PCL-block-polystyrene (PCL-b-PS) copolymers with a photocleavable o-nitrobenzyl group (ONB) between PCL and PS blocks, followed by the photocleavage of ONB with UV-irradiation. The PCL crystallinity showed a conventional sigmoidal evolution both for PCL blocks and PCL homopolymers confined in the large L-domain. However, it increased monotonously with no induction time for PCL blocks but sigmoidally for PCL homopolymers confined in the small L-domain. The substantial differences in crystallization mechanism between PCL blocks and PCL homopolymers confined in the small L-domain are discussed on the basis of chain mobility during crystallization.