Strong photoluminescence from monosubstituted polyacetylenes containing biphenylyl chromophores

Monosubstituted polyacetylenes are generally regarded as unlikely candidate s for photoluminescent materials. We have, however, observed intense deep-b lue emission in a series of photoexcited poly(1-alkynes) (PAs) containing b iphenylyl pendants (-{HC = C[(CH2)(m)-OCO-biphenyl-OC7H15]}(n)-where m = 2, 3, 4, and 9). The photoluminescence (PL) is readily observable by naked ey es under normal room illumination conditions, whose integrated intensity is threefold higher than that of poly(1-phenyl-1-butyne), a well-known highly luminescent disubstituted polyacetylene. A red PL band has also been detec ted in the PAs. Using the extended-Huckel-tight-binding method, we have cal culated the density of states of the PAs, and it is found that the function al pendants have dramatically modified the band states of polyacetylene. Th e strong PL of the PAs is satisfactorily explained by the engineered electr onic structures. (C) 1999 American Institute of Physics. [S0003-6951(99)035 52-4].