FLUORESCENCE PROBING OF MICRODOMAINS IN AQUEOUS-SOLUTIONS OF POLYSOAPS .2. STUDY OF THE SIZE OF THE MICRODOMAINS

The time-resolved fluorescence quenching method has been used to investigate the size (number of repeat units) of microdomains in solutions of poly(disodium maleate-co-decylvinylether) and poly-(disodium maleate-co-hexadecyl vinyl ether) referred to as PS10 and PS16, using pyrene as the fluorescence probe and the dodecylpyridinium ion as the quencher. The shape of the decay curves reveals that the microdomains are somewhat polydisperse in size. In the case of PS10 the number of repeat units per microdomain was found to decrease nearly linearly upon increasing the degree of neutralization of the maleic acid moieties. For PS10 the number of repeat units per microdomain is nearly independent of the polysoap concentration and polymerization degree as well as of the ionic strength and temperature. For PS16, the number of repeat units per microdomain is independent of the polymerization degree but increases much with temperature. Also, it is much larger than that for PS10. Moreover the decay data for PS16 suggest that probe and quencher can rapidly migrate from microdomain to microdomain, on the fluorescence time scale. Overall the results suggest that the formation of a microdomain involves a single polysoap molecule and that several microdomains can be formed from a single polysoap molecule of high molecular weight. Such microdomains are connected by polysoap segments that may be the cause of the probe and quencher migration observed in PS16 solutions and also in PS10 solutions at 60 °C. The migrating molecules would move along these fairly hydrophobic segments. © 1990, American Chemical Society. All rights reserved.