Molecular and supramolecular ordering in confined environments

Crystal and phase morphologies and structures determined by self-organizati on of crystalline-amorphous diblock copolymers, crystallization of the crys tallizable blocks, and vitrification of the amorphous blocks are reviewed t hrough a systematic study on a series of poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymers. On the base of competitions among these thr ee processes, molecular and sueramolecular ordering in confined environment s can be investigated. In a concentration-fluctuation-induced disordered (D -CF) diblock copolymer, the competition between crystallization of the PEO blocks and vitrification of the PS blocks is monitored by time-resolved sim ultaneous small angle X-ray scattering (SAXS) and wide angle X-ray diffract ion (WAXD) techniques. In the case of T-c < T-g(PS-rich), the crystallizati on of the PEO blocks is observed to be confined within the bicontinuous DCF phase due to the rapid vitrification of the PS-rich phase. Overall crystal lization rate, crystal melting behavior, and crystallinity results further confirm the competition between crystallization and vitrification at differ ent temperatures. In an ordered lamellar PEO-b-PS diblock copolymer, the cr ystallization of the PEO blocks is completely confined within the ordered l amellae due to rapid vitrification of the PS layers as observed by time-res olved SAXS and WAXD experiments. From the combined two-dimensional SAXS and WAXD measurements, the crystal orientation within the confined lamellar ge ometry is found parallel to the lamellar surface normal when it is isotherm ally crystallized at 35 degrees C. In an ordered cylindrical PEO-b-PS sampl e, the crystallization of the PEO blocks is also observed to be confined wi thin the ordered cylinders because of rapid vitrification of the PS matrix. The crystal orientation within the confined cylinders is found perpendicul ar to the cylinder axis as it is crystallized at 35 degrees C.