Self-organization behaviours of hemiphasmidic side-chain liquid-crystalline polymers with different spacer lengths
A new and simple series of hemiphasmidic side-chain liquid crystalline polymethacrylates containing biphenyl mesogens with different spacer lengths, 4-[(3,4,5-tridecyloxy)-1-carbonylbenzoate]biphenyl-n-methacrylates (denoted as P-n-BP, n = 2, 4, 6, 8, and 10, n refers to the carbon number of spacers), were designed and successfully synthesized via free radical polymerization. As evidenced by POM, DSC and XRD results, P-2-BP and P-4-BP exhibited the hexagonal columnar (Φh) phase at room temperature, but for P-4-BP, there was a transition from the Φh1 phase to the highly ordered Φh2 phase before isotropization. With longer spacers, P-6-BP and P-8-BP formed a smectic phase at room temperature and transformed into the Φh phase at higher temperatures. For P-10-BP, it only shows a single transition from a smectic phase to an isotropic state. It may be attributed to the fact that the self-organization mechanism of P-n-BP is differential at various temperatures upon varying the spacer length.