Orientation Control and Crystallization in a Soft Confined Phase Separated Block Copolymer

Microdomain orientation and crystallization were examined in a crystalline amorphous diblock copolymer, hydrogenated poly(high-1,4-butadiene)-b-poly(high-3,4-isoprene) (E/MB), which forms cylinders of the crystallizable block (polyethylene, E). Atomic force microscopy (AFM) was used to locally control the orientation of the E cylinders. The orientation process and subsequent crystallization behavior were investigated in situ as a function of temperature by AFM. Fully confined crystallization was observed within the range 25-50 degrees C, with templated and breakout crystallization observed at higher crystallization temperature. The growth rate of templated crystallization along and perpendicular to the existing microdomain structure was measured, and the ratio between these rates was found to increase rapidly with decreasing temperature with a change from similar to 4.8 at 100 degrees C to similar to 8 at 97 degrees C. Two maxima in the degree of orientation of the crystallized regions were found: one at relatively small supercoolings (e.g., 95 degrees C) where the differential in growth rate along and across microdomain boundaries is high and one at high supercoolings (25-50 degrees C) where crystallization is completely dominated by nucleation.