Crystallization and Melting Behaviors of PEO Nano-layer Crystals Confined in between Two PS nano Glassy layers

摘要

Phase transitions of polymers taking place within confined geometries in the nanometerrnlength scale may exhibit different transition behaviors from those in the bulk [1]. One ofrnapproaches to construct nano-confined environments is to use diblock copolymers as templates.rnBelow the order-disorder transition temperature of diblock copolymers, phase morphologies suchrnas lamellae, cylinders, spheres, gyroids, and hexagonally perforated layers (HPL) can form [2].rnAs long as the matrix phase possesses a high glass transition temperature (T_g) in these orderedrnstructures, and another component self-orders to form crystals which have a lower meltingrntemperature (T_m) compared with the T_g, a tailored nano-confined crystallization is achieved [3].rnHowever, in the mechanically aligned bulk samples, nano-defects such as edge and screwrndislocations form. Boundaries of multiple domains are grains which intrinsically generaterndefects [4]. As in the case of PEO-b-PS lamellar morphology, for example, the cross talks occurrnbetween neighboring PEO layers, and they certainly affect the PEO crystallization behaviors inrnthis confined environment. An ideal case to construct a confined single lamella environment isrnto obtain one PEO nano-layer sandwiched by two PS nano-glassy walls. Since these two thin PSrnlayers possess a T_g~(PS) which is higher than the T_m~(PEO) of PEO crystals, the PEO blocks has torncrystallize within this nano-layer confined in one dimension (1D) along the lamellar layer normalrn( n?) without any defects.