Synthesis and characterization of side-chain liquid-crystalline block-copolymers containing laterally attached photoluminescent quinquephenyl units via ATRP

A series of novel side-chain liquid-crystalline polymers (SCLCPs) consisting of laterally attached photoluminescent p-quinquephenyl (QQP) pendants with different flexible terminal- and/or side-alkoxy chains were synthesized via atom transfer radical polymerization (ATRP). Homopolymers (HP1–HP3) and block-copolymers (PSP1–PSP3 and PEOP1–PEOP3), where QQP units were copolymerized with styrene or ethylene oxide monomers, possessed the number average molecular weights (Mn) of 8.7–26.0 × 103 with narrow PDI values of 1.08–1.26. Various characterization techniques of polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to investigate their mesomorphic properties, and all homopolymers and block-copolymers exhibited the nematic phase affected by the flexible terminal- and/or side-alkoxy chains of the conjugated rod-like pendants. In addition, the photophysical properties of these polymers were measured by UV–vis and photoluminescence (PL) spectroscopies, which showed blue PL emissions with rather high fluorescence quantum yields in solutions.