Laser flash photolysis and time-resolved fluorescence measurements of the aggregation number of SDS-biopolymer complexes.
Aqueous solutions of 0.5% sodium carboxymethyl cellulose, NaCMC, and 2-hydroxyethyl cellulose, HEC, and variable concentration of sodium dodecyl sulfate, SDS, were studied by the intensities ratio of pyrene fluorescence bands (I/III and monomer/excimer) and conductance measurements to determine the critical aggregation concentration, cac, and the degree of micellar dissociation, alpha, respectively. The cac of these systems is close to 2-4 x 10(-3)M and values of alpha are consistent with the formation of SDS micelles adsorbed cooperatively to the polymer backbone. Laser flash photolysis (LFP) and time-resolved fluorescence (TRF) techniques were employed to determine the micellar aggregation number, N, using the probes flavone and pyrene, respectively. The obtained N for HEC/SDS and NaCMC/SDS were 48 and 68, respectively. The presence of the counterions at the NaCMC backbone is the main factor responsible for this number. Besides, the transient spectra of flavone and present in 0.5% HEC or NaCMC with and in absence of SDS are discussed. Flavone triplet state exit rate constant from the biopolymer/SDS complexes showed that these systems are completely different from a pure SDS micelle.
Silvério
Cristina A
CA
Departamento de Química da Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto-USP, Av. dos Bandeirantes, 3900 Ribeirão Preto, SP 14040-901, Brazil.
Okano
Laura T
LT
D001704:Biopolymers / Q000737:chemistry*; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry; D007834:Lasers; D008856:Microscopy, Fluorescence / Q000379:methods; D010782:Photolysis; D011721:Pyrenes / Q000737:chemistry; D012967:Sodium Dodecyl Sulfate / Q000737:chemistry*; D013499:Surface Properties; D013997:Time Factors
D001704:Biopolymers; D005456:Fluorescent Dyes; D011721:Pyrenes; D012967:Sodium Dodecyl Sulfate; D002482:Cellulose; D002266:Carboxymethylcellulose Sodium