Chemical Modification of Acrylamide Polymers in Aqueous Solution

Abstract

The world market for synthetic water-soluble polymers was about 950,000 metric tons in 1994.¹ Among them, acrylamide copolymers are used extensively in water treatment as flocculants, coagulants and dispersants. The activities of these polymers are closely related to their molecular weights and structures, especially the nature of the pending groups. One can manipulate the polymerization process to achieve the desired molecular weights. Low molecular weight polymers are usually made in solution with chain transfer reagents. Inverse emulsion polymerization and gel polymerization are commonly used to produce high molecular weight polymers. The desired functionalities of the copolymers can be introduced by using proper monomers or by post-modifications of the acrylamide polymers. Copolymerization of acrylamide with the desired comonomer is usually the method of choice for commercial production. For example, copolymerization of acrylamide and 2-(N-acrylamido)methylpropanesulfonic acid (AMPS) salt is used to produce both high molecular weight flocculants and low molecular weight dispersants. Acrylamide and 2-(dimethylamino)ethyl acrylate methochloride (DMAEM. MCQ) copolymerize to produce high molecular weight flocculants. However, this method is sometimes restricted by the availability of the desired comonomers. The solubility, hydrolytic stability, and the reactivity of the comonomer can also cause processing difficulties. In some cases, post-modification of acrylamide copolymers can be a good alternative for producing the desired polymers. The aminomethylation of poly(acrylamide) (Mannich Reaction) to produce cationic coagulants and flocculants,² the hydrolysis of poly(acrylonitrile) to poly(acrylic acid) as dispersants,³ and the sulfonation of styrene-maleic anhydride copolymers to produce sulfonated dispersants⁴ are commonly practiced in the industrial water treatment industry. In this work, the modification of acrylamide copolymers with some primary amines was studied.