AMPHIPHILIC ALTERNATING CARBAZOLE COPOLYMERS - PHOTOPHYSICAL PROPERTIES OF POLY[N-VINYLCARBAZOLE-ALT-CITRACONIC ACID] IN AQUEOUS-SOLUTION

Amphiphilic polyelectrolytes containing carbazolyl chromophores (a-CzC a) were prepared by hydrolysis of alternating copolymers of N-vinylcar bazole (VCz) and citraconic anhydride and their fluorescence propertie s were compared with those for alternating copolymers of VCz and malei c acid (a-CzMa) and random copolymers of VCz and methacrylic acid (r-C zMA(x)) in aqueous solution. The fluorescence spectrum of a-CzCa, deri ved from the anhydride copolymer with the equimolar monomer feed ratio , showed a predominant monomer emission in both organic and aqueous so lutions, while the fluorescence intensity changed drastically upon dis sociation of carboxyl groups in aqueous solution and had a minimum val ue at acidic pH which was rather smaller than that for the correspondi ng random copolymer. The solution behavior showed that a-CzCa had a le ss hydrophobic character and thus retained a loose form even at low pH . Therefore, the remarkable self-quenching occurring in a-CzCa may be caused primarily by efficient energy migration to very few quenching s ites. Quenching experiments gave additional evidence for hydrophilicit y of a-CzCa. The fluorescence of a-CzCa at pH 3 was found to be quench ed less efficiently by an amphiphilic quencher, bis(2-hydroxyethyl) te rephthalate (BHET), compared with the corresponding random copolymer.