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vol.53 número2SYNTHESIS AND CHARACTERIZATION OF THE LAMELLAR OXYCHLORIDE C0(2)CU4TE4O11CL4PREPARATION AND PROPERTIES OF CHITOSAN HYBRID FILMS FROM MICROWAVE IRRADIATED SOLUTIONS índice de autoresíndice de assuntospesquisa de artigos
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Journal of the Chilean Chemical Society

versão On-line ISSN 0717-9707

Resumo

URBANO, BRUNO et al. SELF-ASSEMBLY OF TRIBLOCK COPOLYMERS IN AQUEOUS SOLUTION. J. Chil. Chem. Soc. [online]. 2008, vol.53, n.2, pp.1507-1510. ISSN 0717-9707.  http://dx.doi.org/10.4067/S0717-97072008000200013.

The aggregation of PE4VP-b-PS-b-PE4VP block copolymers was studied in aqueous solution. Triblock copolymers P4VP-b-PS-b-P4VP were synthesized by sequential anionic polymerization of poly(styrene) and poly(4-vinylpirydine) using sodium naphthalene as a bifunctional initiator. Subsequently, the 4-vinylpyridine units were quaternized with ethyl bromide to obtain cationic PE4VP-b-PS-b-PE4VP block copolymers. Both star and crew-cut micelles were formed. The concentrations at which micelles are formed cmc were determined, by steady-state and time-resolved fluorescence probing methods, as a function of quatemization degree. The results indicate that cmc of crew-cut micelles increases with increasing charge density of the PE4VP blocks. For star micelles there is not a clear dependency of cmc with the percentage of quatemization. The lifetime of pyrene fluorescence and the ratio I1/I3 were determined at concentrations of copolymers well above the cmc, and the results show that the location of pyrene into the micelle changes with the charge density of the micelle corona. The micropolarity sensed by pyrene decreases with increasing quatemization degree. The presence of aggregates was confirmed by transmission electronic microscopy.

Palavras-chave : Triblock copolymers; critical micelle concentration; micelles; fluorescence probing methods; pyrene.

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