Nonionic hydrophiles

Cationic, anionic, and amphoteric surfactants derive thek water solubiUty from thek ionic charge, whereas the nonionic hydrophile derives its water solubihty from highly polar terminal hydroxyl groups. Cationic surfactants perform well in polar substrates like styrenics and polyurethane. Examples of cationic surfactants ate quaternary ammonium chlorides, quaternary ammonium methosulfates, and quaternary ammonium nitrates (see QuARTERNARY AMMONIUM compounds). Anionic surfactants work well in PVC and styrenics. Examples of anionic surfactants ate fatty phosphate esters and alkyl sulfonates. 

Nonionic hydrophilic Polyethylene glycol Soluble starch, methyl cellulose, pullulan Dextran Above samples plus hydroxyethyl cellulose, polyvinyl alcohol, polyacrylamide Distilled water 0.01 N NaOH DMSO Buffer or salt solution (e.g., 0.1— 0.5 M NaNO,)... 

Nonionic, hydrophilic Polyethylene oxide, polyethylene glycol Polyviny alcohol, hydroxyethyl cellulose, polyacrylamide Pure water 0.1-0.2 M salt/buffer, pH 7... 

Table 1 Nonionic, Hydrophilic Monomers Used for Hydrogel Synthesis... 

Nonionic hydrophilic PEO blocks have also been combined with a variety of other hydrophobic blocks, including PI [135], poly(amino acids) [136], aliphatic polyesters [137], etc. It is not possible to review all the published works on these copolymers due to space limitations. We will therefore only present a selected example. 

From these and other experiments a construction was developed that included a core of nonionic hydrophilic polyurethane. The core served as a reservoir for ionized salt. A layer of anionic gel was placed on one side of the core a layer of cationic gel was placed on the opposite site. A current passed through the gel caused the cation to migrate into the anionic gel and led the gel system to contract. When the current flow was reversed, the ions returned to the reservoir. 

The bile salts have a peculiar molecular structure compared with ordinary detergents, possessing both an ionic polar group and nonionic hydrophilic hydroxyl groups. These molecules might, therefore, have characteristics related to both anionic and nonionic detergents. 

Emulsifier-free latices are useful not only for industrial purposes but also for studies on colloidal properties (1, 2) and medical applications (3, h). Various methods have been tried to prepare characteristic emulsifier-free latices (5-8). Among them, copolymerization of hydrophobic monomers with hydrophilic comonomers has been the most applicable one (7, 8). There have been many studies on the effects of ionic comonomers on the kinetics of aqueous copolymerization and the properties of the resulting latices, but nonionic hydrophilic comonomers have rarely been used for these purposes. 

Synthetic detergents may have anionic, cationic, or nonionic hydrophilic functional groups. Of these detergents, only Gardol is a carboxylate salt and forms a precipitate in hard water. 

Sorbitan fatty acid esters are produced by polymerization of ethylene oxide to sorbitan fatty acid esters. The resulting polyoxyethylene sorbitan esters are nonionic hydrophilic emulsifiers. They are used in bakery products as antistaling agents. They ate known as polysorbates with a number as indication of the type of fatty acid used (e.g., lauric, stearic, or oleic acid). 

The complexes of poly(methyl methacrylate) stereoisomers or polymeric adds with nonionic hydrophilic polymers, the complexes between oppositely charged polyelectrolytes or of biological macromolecules and synthetic high molecular weight substances are known. Reactions involving polyelectrolytes24,25) have been studied most extensively. However, only little is known about the complexes with coordinate bonds28,159). 

Figure 18 Influence of different cream bases on the photostability of Retinoic Acid. A, Basis cream DAC B, hydrophilic ointment with water DAB C, nonionic hydrophilic cream DAB ...

Steric factors in the surfactant molecule, such as the presence of a bulky hydrophilic or hydrophobic group, inhibit micellization more than they do adsorption at the aqueous solution-air interface. On the other hand, electrical factors such as the presence of an ionic, rather than a nonionic, hydrophilic group in the surfactant molecule, appear to inhibit adsorption at the aqueous solution-air interface more than they do micellization. 

---