Design and Synthesis of Luminescent Liquid Crystalline Polymers with “Jacketing” Effect and Luminescent Patterning Applications

To fabricate luminescent liquid crystalline polymers (LLCs), two monomers 2,5-bis[(4′,4″-dibutyloxy)tetraphenylphthalate]styrene (M1) and 2,5-bis[(4′,4″-dibutyloxy)tetraphenylethylene]styrene (M2) have been successfully designed and synthesized. Although M1 and M2 show no LC property and M1 is nonemissive in the solid state, M2 shows very strong solid-state emission with a fluorescence quantum yield (ΦF) of 27.7%. The better solid-state luminescence behavior of M2 than M1 can be attributed to the elimination of the photoinduced electron transfer effect as suggested by the theoretical calculation results. The structural difference between M1 and M2 also results in a dramatical difference of polymerizability. While M1 can be readily homopolymerized using the radical polymerization method, M2 can only be copolymerized under harsh conditions. The resulting homopolymer poly{2,5-bis[2-(4,4′-dibutyloxy)tetraphenylphthalate]styrene} (P0) and copolymers poly{2,5-bis[(4′,4″-dibutyloxy)tetraphenylethylene] styrene}x–{[2,5-di(hexylformate)]styrene}y (Pns, n = 1, 2, 3) all show typical columnar liquid crystal phase (ColH) as demonstrated by the variable-temperature 1D wide-angle X-ray diffraction results. Similar to their corresponding monomers, P0 is weakly emissive with a low ΦF of 2.0% in the solid state whereas Pns exhibit strong solid-state fluorescence with ΦF in the range 18.0–45.1%. The ΦF value of the copolymers increases with the increasing contents of composition M2. The obtained Pns with good solution processability can be used to prepare highly luminescent two-dimensional patterns with high resolution through nanoimprint lithography, which reveals that Pns find potential applications in advanced optoelectronic and biophotonic devices.