Solution Crystallization Behavior of Crystalline−Crystalline Diblock Copolymers of Poly(ethylene oxide)-block-poly(ε-caprolactone)

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Abstract

The crystallization behavior of crystalline−crystalline (CC) diblock copolymers has been shown to be dependent on the crystallization temperature and relative molecular size of each component. The behavior of copolymers with similar crystallization temperatures is controlled by the block with the larger weight fraction and solvent−polymer interactions. Using samples of poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL), dilute solution crystallization methods were investigated to determine their role in crystallization of CC copolymers. A single crystal of one block, either PEO or PCL (the first block), crystallized first with the second block segregated to the crystal basal surfaces. For the first time, solvent quality and homopolymer seeds were introduced to manipulate crystallization of the block with the smaller weight fraction to crystallize first and form the lamellar single crystal. In addition, subsequent crystallization of the tethered chains (the second block) on the surface was also observed, depending upon the molecular weight of the second block and crystallization conditions. These crystallites formed by the second block exhibited preferred orientations on the crystal surface as observed by electron diffraction. It is believed that this orientation was induced by “soft” epitaxy between the fold surfaces of the adjacent single crystals of the first block formed by the initial crystallization.

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