Surfactants combined with associating polymers

The opposite effect on quenching by neutral molecules when small amounts of detergent are added to aqueous solutions of 3 could be attributed to several possible factors. First, the addition of detergent to the polymer may help in affording a more hydrophobic environment in its vicinity that may enhance the polymer-small molecule association. Also, since surfactants such as DTAB are well known to solubilize organic molecules in water, it appears reasonable that clusters of the detergent may combine with the neutral quenchers and function as chaperones to increase their effective solubility and thus enhance the complex formation with the polymer. 

An elegant innovation to aid the study of polymer/surfactant interaction was the introduction of a fluorescent label directly onto the polymer molecule by covalent bonding. [See reviews by Winnik (43,44).] This approach has been particularly useful in systems, such as combinations of nonionic polymers and nonionic surfactants, where interaction is weak. For example, pyrene-labeled hydroxypropylcellulose (HPC) gave evidence of association with weakly reactive OTG (n-octyl-P-D-thioglucopyranoside) but only at concentrations near its c.m.c. (119). Experiments with pyrene-labeled PNIPAM have been reported by Winnik et al. (120), who obtained evidence of noncooperative association of this polymer with anionic and cationic surfactants. A polymer that has been terminally labeled with pyrene groups is PEO (121) in mixtures with SDS at lower concentrations fluorescence data indicated the polymer chain cyclized. At higher concentration the pyrene groups were located in separate micelles. 

The above data summarize in vitro information concerning protective effects associated with polymer/surfactant combinations. Reference is made finally to similar results from in vivo ( patch ) tests on skin using 5% SDS solutions (21). While Polymer JR 400 in concentrations of 0.1, 0.25, and 0.5% is barely effective, a 1% solution reduced the inflammatory reaction by about 50% and a 2% solution virtually eliminated it (21). 

Nonpolar block copolymers with functional polar groups combine the properties of a block copolymer with those of functionahzed homopolymers. End functionalized polymers can self-associate in solution in a manner analogous to low-molecular-weight surfactants, whereas the solid-state properties of the precursor polymer are greatly influenced by the presence of small amounts of polar groups since their aggregation persists in bulk [31]. The interaction of a polymer chain with a surface in solution can be altered and sometimes controlled by the nature and placement of specific functional groups. 

Emulsions are dispersions of one liquid in another liquid, most commonly water-in-oil or oil-in-water. The total interfacial area in an emulsion is very large, and sinee flie interfacial area is associated with a positive free energy (the interfacial tension), the emulsion system is thermodjmam-ically unstable. Nevertheless, it is possible to make emulsions with an excellent long-term stability. This requires the use of emulsifiers that accumulate at the oil/water interface and create an energy barrier towards flocculation and coalescence. The emulsifiers can be ionic, zwitterionic, or nonionic surfactants, proteins, amphiphilic polymers, or combinations of polymers and surfactants. The structure of the adsorbed layer at the water/oil interface may be rather complex, involving several species adsorbed directly to the interface as well as other species adsorbing on top of the first layer. 

Associative thickeners are also useful thickeners for cosmetic and toiletry products. These products types are most compatible with anionic and non-ionic co-ingredients, give clear formulations and work most effectively in neutral or mildly alkaline environments (to ensure the polymer is fully in solution). Associative thickeners also work well in surfactant systems since the hydrophobic groups in the polymer is able to interact with the micelle structure already present in such systems. Some grades are not effective at giving high viscosity under low shear conditions but the use of thickener combinations can address such limitations. 

The development of novel polymer latex particles, especially in the domain size lower than 100 nm, makes them very attractive, for instance, in nanotechnologies and bionanotechnology (which combines biosystems and nanofabrication). At first, innovating heterogeneous polymerization techniques such as those taking place in surfactant assemblies (microemulsions, vesicles etc.) or using polymerizable amphiphiles should provide polymer colloids with unexpected properties. In addition, the possibility to associate organic and... 

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