Phase morphologies in block copolymers of polystyrene and columnar liquid crystalline polydiethylsiloxane

摘要

Well-defined diblock copolymers of polystyrene (PS) and polydiethylsiloxane (PDES) were synthesized by sequential anionic polymerization. By means of differential scanning calorimetry (DSC), the PDES blocks were shown to exist in the columnar mesophase at ambient temperatures. PS-b-PDES block copolymers with a PS content >21 wt.- build lamellar structures, below this percentage PS cylinders were found that are arranged in sheets, forming a (somewhat irregular) overall lamellar structure. Both the low PS content at which the transition from lamellar to cylindrical structures takes place, as well as the peculiar organization of the PS cylinders in the latter were ascribed to the mesomorphic nature of the PDES block in combination with the fact that the glass transition temperature of PS (T-g approximate to 100 degrees C) is much higher than the isotropization temperature of the PDES block (T-i (ca. 50 degrees C). References: 23