Fluorescence probing of microdomains in aqueous solutions of polysoaps. 2. Study of the size of the microdomains

Abstract

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 PSÍ6, 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.

Conformational Changes of Pyrene-Labeled Polyelectrolytes with pH: Effect of Hydrophobic Modifications

“…15,16 Fluorescence quenching studies have revealed that these HM polymers form large numbers of relatively small nanodomains. [9][10][11][12][13] The presence of hydrophobic nanodomains in aqueous solutions enables the HM polymers also to remove organics from aqueous solutions. Because most HM polymers are sensitive to pH and ionic strength, regulation of these variables can also be used to manipulate conformation and solution rheology.…”

Molecular concepts, self-organisation and properties of polysoaps

“…Whereas polymers with decyl tails behave like polysoaps at any degree of dissociation, polymers with hexyl tails act as polysoaps only when less than 40%, polymers with pentyl tails when less than 30% and polymers with butyl tails when less than 20% of the -COOH groups are deprotonated [54,176,177,181]. As for the latter examples, much hydrophobicity derives from the polymer backbone in the partially dissociated state, and these polymers may be considered as intermediate cases [54,169,170,182,186,190,196]; 34: [191,192]; 35, 37, 38: [168]; 36: [314] between the longitudinal knotting of surfactant units and the lateral knotting found in classical polysoaps (see Figs, le and If). The alternative to "main chain spacers" is the separation of backbone and surfactant fragments by "side chain spacers" (Fig.…”

“…The tails have to be enlarged to counterbalance the increasing charge in the polymer with increasing neutralization. Only if the tail lengths exceed octyl polysoap behaviour is observed independently of the degree of neutralization [186,190,192,196]. An analogous effect may be responsible for the markedly reduced viscosities seen for polysoaps with low, just sufficient hydrophobe content when a certain amount of hydrophobic solubilizate is added [47,49,130]: the incorporated hydrophobic compounds mimic a decrease of the HLB.…”

“…This is particularly important if very large and bulky probes such as ET 30 are employed [212] which are about of the same order of size as the aggregate. Furthermore, assumptions often have to be made to enable a treatment of the acquired data which cannot be verified [196,370]. Therefore results derived from such studies may be ambiguous and the conclusions even misleading, and several techniques should preferably be combined.…”

Metastable state of amphiphilic polysaccharide solutions

“…Depending on their hydrophilic-lipophilic balance, i.e., on both the extent and the length of hydrophobic substitution, water-soluble amphiphilic polymers can behave as polysoaps [1][2] and/or associating polymers [3][4][5]. They possess properties superior to those of conventional hydrophilic polymers.…”