Polymerization of Alkyl Acrylates and Alkyl Methacrylates with Starch

A series of C4-C 12 alkyl acrylates and methacrylates was polymerized with starch by irradiating starch-monomer mixtures with 60CO. Homopolymers were extracted with cyclohexane. The amounts of insoluble versus soluble synthetic polymer in polymerizations run with alkyl acrylates varied less with the chain length of the alkyl substituent than in the polymerizations run with alkyl methacrylates: and the poly(alkyl acrylate) contents of cyclohexane-insoluble fractions were all in the 38-45% range. Synthetic polymer contents of the products from butyl, hexyl, and decyl methacrylates were also close to this range. Octyl and lauryl methacrylate, however, gave high conversions to cyclohexane-soluble poly(alkyl methacrylate) along with little or no unextractable synthetic polymer in the starch-containing fractions. Poly(lauryl methacrylate) could be rendered insoluble by incorporating a small amount of tetramethylene glycol dimethacrylate in the polymerization mixture. In a series of polymerizations run with hexyl acrylate and hexyl methacrylate, lower irradiation doses led to more cyclohexane-soluble polymer and less synthetic polymer in the starch-containing fractions. Enzymatic digestion of starch-containing polymers gave synthetic polymer fractions that were largely insoluble in cyclohexane. Crosslinking is, therefore, probably taking place during these polymerizations; however, we could not eliminate the possibility that reduced solubility was caused by small amounts of residual carbohydrate in these polymer fractions. Ceric ammonium nitrate-initiated polymerizations of butyl acrylate, hexyl acrylate, and butyl methacrylate with starch gave cyclohexane-insoluble polymers that contained 33-39% synthetic polymer. The higher alkyl acrylates and methacrylates produced little or no polymer under these conditions. Starch-containing fractions were tested as absorbents for hydrocarbons. Products prepared from decyl acrylate and lauryl acrylate absorbed about 9 g of isooctane per 19 of polymer, whereas the lower alkyl monomers gave polymers with lower absorbency.