Self-assembled block copolymers as matrix for multifunctional materials modified with low-molecular-weight liquid crystals

Meso/nanocomposite films made of low-molecular-weight nematic 4′-(hexyloxy)-4-biphenyl-carbonitrile (HOBC) embedded in poly(styrene-block-ethylene oxide) (PSEO) diblock copolymer have been prepared by using solvent-induced phase separation at room temperature. Their phase separation behavior has been investigated by morphological and viscoelastic analyses as a function of HOBC content and preparation conditions. Self-assembly of block copolymer in HOBC/PSEO systems containing 5, 10, 30 and 50 wt.% HOBC leads to submicron phase segregation of HOBC. Moreover, narrower droplet size and good distribution of nematic liquid crystal droplets in the self-assembled PSEO matrix have been observed. Thus solvent-induced microphase separation of poly(ethylene oxide)-block provokes segregation of the liquid crystal as a mesophase. Self-assembled HOBC/PSEO systems maintain generated droplet-like morphology of the HOBC phase even after 3 months, thus confirming the possibility of obtaining multifunctional materials with stable and well-defined morphologies based on block copolymer-dispersed liquid crystals as optically transparent matrices. This kind of material generates thermally reversible material for optoelectronics based on room temperature self-assembling block copolymers matrices.