| Abstract
| - Biphenyl- (Biph-) containing 1-alkynes (3 and 4) and their polymers (1 and 2) with varyingbridge groups and spacer lengths were synthesized and the effects of the structural variation on theirproperties, especially their mesomorphism and photoluminescence behaviors, were studied. The acetylenemonomers 3(3) [HC⋮C(CH2)3O−Biph−OCO(CH2)10CH3] and 4(m) [HC⋮C(CH2)mOCO−Biph−OCO(CH2)10CH3, m = 3, 4] were prepared by sequential etherization and esterification reactions of 1-alkynes. While3(3) exhibits enantiotropic crystal E and SmB mesophases, its structural cousin 4(3) displays only amonotropic SmB phase. Enantiotropic SmA and SmB mesophases are, however, developed when the spacerlength is increased to 4. Polymerizations of the monomers are effected by Mo-, W-, Rh-, and Fe-basedcatalysts, with the WCl6−Ph4Sn catalyst giving the best results (isolation yield up to 85% and Mw up to59000). The polymers were characterized by IR, UV, NMR, TGA, DSC, POM, XRD, and PL analyses.Compared to 1(3), 2(3) shows a red-shifted absorption, a higher Ti, and a better packed interdigitatedbilayer SmAd structure, while the mesophase of 2(4) involves monolayer-packing arrangements of themesogens. Upon photoexcitation, 1(3) emits almost no light but 2(m) gives a strong ultraviolet emission(λmax ∼ 350 nm), whose intensity increases with the spacer length.
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