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Polymeric Ethers are formed by polymerization of monomeric alkylene oxides, generally ethylene or propylene oxide. The molecular weights of these polymers may be quite low (e.g., PEG-4) or as high as several million (e.g., PEG-115M). Polyethers possess terminal hydroxyl groups, which also makes them Alcohols. They have the structure:
where R may be H or lower alkyl, and n is the number of repeating monomer units.
Homopolymeric ethers are formed when a single monomer is used during polymerization. Random copolymers are derived from the reaction of blends of alkylene oxides. Polymeric Ethers of the block type are prepared from a central homopolymeric ether, the terminal hydroxyl groups of which are then allowed to react with another alkylene oxide.
In cosmetics the low molecular weight polymeric ethers are used as humectants and cosolvents; the high molecular weight polymers are powerful thickening agents in aqueous systems and provide lubricity. The block polymers are important emulsifying and wetting agents. Finally, the homopolymers of propylene oxide (e.g., PPG-17) possess lipid-like characteristics and may be used to replace other lipids, such as mineral oil or fats, in cosmetic products. Many Carbohydrates (e.g., Cellulose) and polymeric glycerin derivatives (e.g., Polyglyceryl-10 Decaoleate; see Glyceryl Esters) are also Polymeric Ethers. |