Poly[(side-on mesogen)-alt-(end-on mesogen)]: A Compromised Molecular Arrangement

In recent years, sequence-controlled side-chain liquid crystal polymers (SCLCPs) have gained extensive interest because mesogenic units with different lengths and distributions can form various ordered sequences, which further endow LCP materials with diverse functions. In this manuscript, a side-chain side-on maleimide-containing monomer 2,5-bis-(4-butoxy-benzoyloxy)-benzoic acid 6-(2,5-dioxo-2,5-dihydro-pyrrol-1-yl)-hexyl ester (Y1801) and a side-chain end-on styrene-containing monomer 4′-[6-(4-vinyl-phenoxy)-hexyloxy]-biphenyl-4-carbonitrile (Y1802) are combined in one single macromolecular chain and orderly polymerized in an alternative sequence to form an alternating copolymer Poly(Y1801-alt-Y1802). The chemical structure and alternating sequence of Poly(Y1801-alt-Y1802) are confirmed by GPC and NMR techniques. The combination of DSC, POM, and WAXS data indicates that, although the side-on homopolymer PY1801 and the end-on homopolymer PY1802 both exhibit the nematic phase, their alternating copolymer Poly(Y1801-alt-Y1802) shows an interdigitated smectic A phase, a compromised molecular arrangement instead. In addition, a strong fluorescence emission of Poly(Y1801-alt-Y1802) is observed, which might provide this novel alternating-structured liquid crystal polymer with potential applications in luminescent materials and devices.