Synthesis, Chiroptical Properties, and Photoresponsiveness of Optically Active Poly(m-phenyleneethynylene)s Containing Azobenzene Moieties

The Sonogashira-Hagihara coupling polymerization of 3',5'-diiodo-4'-hydroxy-N-alpha-tert-butoxycarbonyl-D-phenylglycine ethyl-, hexyl-, and laurylamides 1a-c with p-nonsubstituted, cyano, hexyl, and methoxy 3,5-diethynylazobenzenes 2a-d was carried out to obtain optically active novel poly(m-phenyleneethynylene) with M-w values in the range from 6900 to 15 400 in 62-84% yields. CD and UV-vis spectroscopic data indicated that the polymers adopted thermally stable helical conformations in CH2Cl2 and N,N-dimethylformamide. Poly-(1b-2a) further formed a chirally aggregated structure. The azobenzene moieties of the polymers underwent reversible photoisomerization upon UV- and visible-light irradiation, accompanying the changes of the higher-order structures.