Synthesis and characterization of novel rod-coil diblock copolymers of poly(methyl methacrylate) and liquid crystalline segments of poly(2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene)

Liquid crystalline diblock copolymers with different molecular weights and low polydispersities were synthesized by atom transfer radical polymerization of methyl methacrylate (MMA) and 2,5-bis[(4-methoxyphenyl) oxycarbonyl]styrene (MPCS) monomers. The block architecture (coilconformation of MMA segment and rigid-rod of MPCS segment) of the copolymer was experimentally confirmed by a combination of ¹H nuclear magnetic resonance and gel permeation chromatograph techniques. The liquid crystalline behaviour of the copolymer was studied using differential scanning calorimetry and polarized optical microscope. It was found that the liquid crystalline behaviour was dependent on the number average molecular weight of the rigid segment. Only those copolymers with M_n(GPC) of the rigid block above 9200 g mol^-1 could form liquid crystalline phases higher than the glass transition temperature of the rigid block. The random copolymers MPCS-co-MMA were also synthesized by conventional free radical polymerization. The molar content of MPCS in MPCS-co-MMA had to be higher than 71% to maintain liquid crystalline behaviour.