Structural aggregates of rod-coil copolymer solutions

The optoelectronic properties of rod-coil diblock copolymers with pi-conjugation are greatly affected by molecular packing, which is closely related to their micellar morphology. Self-assembly of rod-coil block copolymer B(y)A(x) in a selective solvent for its coil block is studied by using dissipative particle dynamics, where B(y)A(x) denotes the polymer comprising of y rodlike B beads and x coil-like A beads. The influences of polymer concentration, component compatibility, solvent quality for coil block, rod-block length, and pi - pi interaction on the resulting aggregate conformations are examined. It was found that distinctly different from coil-coil copolymers, the aggregates of rod-coil copolymers exhibit morphological and structural diversity induced by the intrinsically rigid nature of the rod blocks. In general, the aggregate adopts the overall shape of sphere, cylinder, perforated sheet, or network. The morphology of the rod-block domain within aggregate is even richer and the interesting structures such as porous sphere, spherical spiral, helical bundles, discrete chunks, and nematic cylinder are observed. The short-range order parameter indicates that as rod length is long enough, neighboring rods begin to orient parallel to one another and nematic domains appear. Moreover, in the presence of pi - pi interactions, the neighboring rods within the B domains become more coherently oriented and smectic domains can thus be formed. (c) 2011 American Institute of Physics. [doi:10.1063/1.3537977]