| Abstract
| - Polypropiolates with different kinds and numbers of substituents (−{(R)CC[CO2(CH2)6−OCO−Biph−OC7H15]}n−; R = H (1), CH3 (2), C6H5 (3), Biph = 4,4‘-biphenylyl) were synthesized, and theeffects of the structural variations on the mesomorphic and luminescent properties of the polymers wereinvestigated. The propiolate monomers RC⋮CCO2(CH2)6OCO−Biph−OC7H15 [R = H (8), CH3 (9), C6H5(10)] were prepared by esterification of (substituted) propiolic acids (RC⋮CCO2H) in high yields. While8 and 9 formed enantiotropic SmA phases, 10 was nonmesomorphic. Polymerizations of the monomerswere effected by Mo- and Rh-based catalysts and polypropiolates with high molecular weights (Mw up to3.5 × 105 Da) were obtained in moderate yields. The polymers were characterized by IR, NMR, TGA,DSC, POM, XRD, UV, and PL analyses. All the polymers were thermally stable. Polymer 1 obtainedfrom the Mo catalyst possessed a lower stereoregularity but exhibited a better-packed monolayer SmAmesostructure, in comparison to the polymer from the Rh catalyst. With an increase in the backbonerigidity from 1 to 3, the glass transition temperature of the chain segments increased, but packing orderof the mesogen pendants decreased. Upon photoexcitation, all the polymers emitted UV light of 369 nm.The emission efficiency was dramatically affected by the chain stereoregularity and backbone structure,with 2 exhibiting a quantum yield as high as 0.7.
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