Extractability of homopolymer of methyl methacrylate from, its graft copolymers with starch

A study has been made of factors which influence the efficiency of extraction of homopolymer of methyl methyacrylate from its graft copolymers with granular corn starch. The moisture content plays a significant role in the extractability of homopolymer; about 25% moisture seems optimum for many samples, with extractability of homopolymer falling sharply at lower moisture levels. In a series of solvents, the efficiency of removal of ungrafted homopolymer varies in a manner roughly paralleling the relative solvating efficiencies of the various solvents for the homopolymers, as indicated by the reported values of appropriate parameters for polymer solutions. For the starch/PMMA system, chloroform and dichloroethane are about equally efficient, and either is superior to benzene, which in turn is better than toluene, methyl ethyl ketone, or acetone. Soxhlet extraction, though commonly used for graft copolymers, is not as effective for the granular starch/PMMA system as is tumbling the heated mixture of solvent and polymer in a closed container. This is probably due to inefficient percolation of the solvent through the swollen syrupy mass of graft copolymer in the Soxhlet thimble.