FLUORESCENCE PROBE TECHNIQUES USED TO STUDY MICELLE FORMATION IN WATER-SOLUBLE BLOCK COPOLYMERS

Micelle formation in water by poly(ethylene oxide)-polystyrene diblock and PEO-PS-PEO triblock copolymers was studied by the fluorescence probe technique using pyrene as the fluorescent dye. Solutions containing 6 X 1(T7 M pyrene and varying block copolymer concentrations were prepared, and four separate features of the pyrene fluorescence were examined. In the excitation spectrum, the (0,0) band shifts from 333.5 nm for pyrene in water to 339.5 nm for polymer-bound pyrene. At the cmc, sharp increases were observed in the total fluorescence intensity and mean fluorescence decay time. From the decay time measurements and fluorescence vibrational fine structure, The location of the pyrene within the polystyrene phase of the micelle can be determined. For the polymer samples of mean degree of polymerization PEO(240)-PS(37) and PEO(102)-PS(41)-PEO(102), we find cmc values in the range of 4 X 10-7 M (6 X 10-3 g/L). © 1990, American Chemical Society. All rights reserved.