Photoluminescence and excimer emission of functional groups in light‐emitting polymers

Abstract

AbstractNear‐UV and blue‐light‐emitting polymers were synthesized with luminescent functional groups in the side chains or in the polymer main chain. The unsubstituted fluorophores, 2,5‐diphenylfuran, 2‐phenylbenzoxazole, and triphenylamine, do not form excimers in solution; however, in the case of polymers, excimer emission was negligible only with 2‐phenylbenzoxazole derivatives. The monomers as well as the polymers, poly(2‐(4‐vinylphenyl)‐benzoxazole), poly{N‐(4‐benzoxazol‐2‐yl‐phenyl)‐N′‐[2‐(methacryloyloxy)ethyl]urea}, and the polyurea of 2‐(4‐aminophenyl)‐5‐aminobenzoxazole with 1,5‐diisocyanato‐2‐methylpentane, were strong blue emitters; photoluminescence shifted to longer wavelengths than that of 2‐phenylbenzoxazole. Light‐emitting polymers containing 2,5‐diphenylfuran derivatives, including poly[2‐(4‐vinylphenyl)‐5‐phenylfuran], poly[2‐(4‐vinylphenyl)‐5‐(4‐tert‐butylphenyl)furan], and poly(N‐[2‐(methacryloyloxy)ethyl]‐N′‐{4‐[5‐(4‐tert‐butylphenyl)‐2‐furyl]phenyl}urea), particularly in solid films, exhibited a strong blue excimer emission. The emission characteristics of polymers with triphenylamine side chains were influenced by the mode of attachment of the luminescent group. A longer spacer group between the lumophore and the polymer main chain successfully minimized excimer emission in poly{N‐[2‐(methacryloyloxy)ethyl]‐N′‐[4‐(N,N‐diphenylamino)phenyl]urea}, showing near UV/violet photoluminescence. Polymers with a shorter connecting group, such as poly[4‐(N,N‐diphenylamino)benzyl acrylate], displayed blue excimer emission. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1634–1645, 2003