Lyophilic groups

A broad range of silicone surfactants are commercially available, representing all of the structural classes—anionic, non-ionic, cationic, and amphoteric. The silicone moiety is lyophobic, i.e. lacking an affinity for a medium, and surfactant properties are achieved by substitution of lyophilic groups to this backbone. The most common functionalities used are polyethylene glycols however, a broad range exist, as shown in Table 2.8.1 [2,3]. 

This micelle is comprised of surfactant molecules consisting of long hydrocarbon tails attached to an anionic lyophilic group. Typically, there are 50-100 molecules in the micelle. Some counterions in the medium are adsorbed on the aggregate, whereas others form the diffuse ionic environment. Some workers believe that there is considerable penetration of the medium into the micelle. Micelles are important for detergent action, with oily dirt particles dissolved in the hydrocarbon interior of the micelle. 

The second group of systems exhibits the liquid-crystalline state only in the presence of a low-molecular-weight liquid (water, for example). These are really lyotropic liquid-crystalline systems in which self-ordering is caused by their amphiphilic character, i.e., the presence of lyophobic and lyophilic groups at the ends of the long molecules. Soaps, lipids, and some types of proteins are members of this group. The specific features of the phase transitions in them will not be examined here. 

A rapid continuous process, not complicated by side reactions, has been reported for the prepn. of isocyanato- from amino-esters. The products can be used for attaching a lyophile group to water-insoluble compounds . A new synthesis of sym. ureas from amines and carbon monoxide has been reported . ... 

The presence of a lyophilic group on the surfactant molecule prevents or retards the complete expulsion of the solute molecules from the solvent as a separate phase, at least at low concentrations. As discussed in Chapter 5, high concentrations of surfactant can lead to a number of interesting and useful phenomena related to the varied aggregate structures that they can form. 

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