Crystalline Morphology of Homopolymers Confined in Isolated Nanodomains

4 Crystalline Morphology of Homopolymers Confined in Isolated Nanodomains 

The crystalline homopolymers spatially confined in nanocylinders can be prepared using the microphase separation of block copolymers, followed by the photocleavage of block junctions (Fig. 10.4), where o-nitrobenzyl (ONB) groups inserted between different blocks are conveniently used for the photocleavage reaetion [48]. Nojima et al. [44—47] synthesized poly(e-eaprolaetone)-WocA -polystyrene (PCL-ft-PS) diblock copolymers with ONB between PCL and 

PS blocks. After forming nanocylinders by the microphase separation of block copolymers (Fig. 10.4a), ONB was cleaved using UV irradiation to get PCL homopolymers confined in nanocyhnders surrounded with PS matrices (Fig. 10.4b), where the vitrification of PS blocks prevented macrophase separation between PCL and PS homopolymers after the photocleavage. As a result, they obtained crystalline PCL blocks and PCL homopolymers both confined in identical nanocylinders with varying diameters. Therefore, it was possible to evaluate the difference in crystallization behavior and crystalline morphology between PCL blocks and PCL homopolymers, and also to clarify the characteristics of homopolymer crystallization spatially confined in nanocylinders. 

The crystal orientation of PCL homopolymers spatially confined in nanocylinders showed that the c-axis of PCL crystals (stem direction of PCL chains) was always perpendicular to the cylinder axis but the crystal growth direction depended significantly on nanocylinder diameter D and crystallization temperature T the h-axis (fastest growth axis of PCL crystals) was parallel to the cylinder axis in nanocylinders with smaller D ( 13.0 nm), whereas the (110) plane of PCL 

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