Influence of alkyl tail length on self-organisation of side-chain liquid crystalline polymers with biphenyl hemiphasmidic mesogens

ABSTRACTA new and simple series of side-chain liquid crystalline polymethacrylates containing biphenyl hemiphasmidic mesogens based on 4-[(3,4,5-trialkan)-1-carbonylbenzoate]biphenyl (denoted as PTmBMA, m = 6, 8, 10, 12, 14, 16, 18, m refers to the carbon number of alkoxy tails) groups was designed and successfully synthesised via free radical polymerisation. The phase structures and transitions of the polymers were investigated by the combination of techniques including differential scanning calorimetry, polarizing microscope, one-dimensional/two-dimensional wide-angle X-ray diffraction, and small-angle X-ray scattering. The experimental results revealed that the liquid crystalline phase structures and behaviours of the polymers were found to be strongly dependent on the alkyl tail length (m). When m = 6, the PTmBMA formed a stable smectic phase above Tg. When m = 8, 10, 12, 14, 16, 18, the sample presented a hexagonal columnar mesophase (Φh), suggesting that the alkyl length has played an important role...