Ethylene, 30 Table commercial preparation

The range of surfactant emulsifiers used in pharmaceutical preparations is illustrated in Table 2. Surfactants are manufactured from a variety of natural and synthetic sources and consequently they show considerable batch-to-batch variations in their homologue compositions and in trace impurities from the starting material. For example, batch variations in the number of neutral phospholipids occur in lecithin surfactants and non-ionic polyethylene surfactants show variations in the number of moles of ethylene oxide. The mechanisms by which such batch variations lead to differences in emulsifying properties are now better understood. Although synthetic and semisynthetic surfactants form by far the largest group of emulsifiers studied in the scientific literature and many of them are available commercially, their use in pharmaceutical emulsions is limited by the fact that the majority are toxic (i.e., haemolytic) and irritant to the skin and mucous... 

The preparation of ionomers involves either the copolymerization of a functionalized monomer with an olefinic unsaturated monomer or direct functionalization of a preformed polymer. Typically, free-radical copolymerization of ethylene, styrene, or other a-olefins with acrylic acid or methacrylic acid results in carboxyl-containing ionomers. The copolymer, available as a free acid, is then neutralized partially to a desired degree with metal hydroxides, acetates, or similar salts. The second route for the preparation of ionomers involves modification of a preformed polymer. For example, sulfonated polystyrene is obtained by direct sulfonation of polystyrene in a homogeneous solution followed by neutralization of the acid to the desired level. Some commercially available ionomers are listed in Table 15.17. 

To prepare Teflon AF series, reactions of hexafluoroacetone (HFA) and ethylene oxide (EO) give rise to defluorinated 2,2-bis(trifluoromethyl)-4,5-difluoro-l,3-dioxole (BDD) monomer, followed by the copolymerization with tetrafluoroethylene (TFE). The physical properties of these amorphous copolymers are dependent upon the compositions in the copolymers as shown in Table 4.8. Currently, there are two commercial grades of Teflon AF polymers produced by DuPont, AF-2400 and AF-1600, which contain the composition of copolymers for which n = 0.87 and 0.65, respectively, where n is the molar ratio of the BDD monomers. 

---