Functional disubstituted polyacetylenes: Synthesis, liquid crystallinity, light emission, and fluorescent photopatterning of biphenyl-containing poly(1-phenyl-octyne)s with different functional bridges

Biphenyl (Biph)-containing 1-phenyl-1-octynes and their polymers are synthesized, and the effects of functional bridge groups on the mesomorphic and optical properties of the polymers are studied. The nonmesomorphic disubstituted acetylene monomers (C₆H₁₃)C≡ C(C₆H ₄)O(CH₂)₁₂O-Biph-OC₇H₁₅ (1), (C₆H₁₃)C≡C(C₆H₄)O(CH ₂)_11- OOC-Biph-OC₇H₁₅ (2), and (C₆H₁₃)C≡ C(C₆H₄)CO ₂(CH₂)₁₂OOC-Biph-OC₇H₁₅ (3) are prepared by multistep reaction routes and converted into their corresponding polymers P1-P3 by a WCl₆-Ph₄Sn catalyst. The structures and properties of the polymers are characterized and evaluated by NMR, TGA, DSC, POM, XRD, UV, and PL analyses. The mesogenic pendants have endowed the polymers with high thermal stability (≥400°C). While P1 exhibits no liquid crystallinity, P2 and P3 form enantiotropic SA phase with a monolayer structure. Upon photoexcitation, the polymers emit blue and blue-green lights of 460 and 480 nm, respectively, in THF with quantum efficiencies larger than 30%. UV irradiation of a thin film of P2 through a mask oxidizes and quenches the light emission of the exposed regions, generating a two-dimensional luminescent photoimage.