(74i) PEO Minority Block Crystallization in Asymmetric PEO-B-PCL Copolymers

Crystalline-crystalline diblock copolymers have unique hierarchical crystallization assemblies based on the interplay of phase separation and crystal nucleation and growth. PEO-b-PCL provides a unique opportunity to study sequential crystallization for mobile amorphous chains with similar crystallization temperatures. Isothermal crystallization of the PCL majority block, T_ISO^PCL, was performed to manipulate PCL crystal thickness and percent crystallinity. Subsequently, the crystallization temperature of the PEO minority block, T_x^PEO, was measured during cooling using DSC. It was found that T_x^PEOincreased with increasing T_ISO^PCL for a number of weight ratios. This phenomenon demonstrated that the PEO nucleation improved compared non-isothermal cooling for both constituents. Additionally, there was a general increase in the PEO block’s crystallinity. Both observations support the idea that a higher concentration of PEO in the interlamellar region is the primary driver for its crystallization behavior thus alleviating any confinement effects.