Graft copolymerization of methyl methacrylate onto lignosulfonate in aqueous medium was investigated. It was found that the H2O2–Fe(II) redox system is very effective for the grafting (Ea = 4.4 kcal/mole). The H2O2/Fe2+ ratio was the most important factor in the graft copolymerization and characteristics of the resultant graft copolymers. In most cases, polymerization for 100 min at 30°C was enough to obtain 80% conversion and 50–60% grafting efficiency. The resultant polymer mixture was subjected to extraction alternately with acetone and water, and the graft copolymer was isolated free from homopolymer and unreacted lignosulfonate. With increasing H2O2/Fe2+ ratio, the grafting ratio showed a maximum at 4, whereas the yield of graft copolymer and number of poly(methyl methacrylate) branches for every building unit of lignosulfonate increased up to a ratio of 4, both values, however, remaining constant above 4. The graft copolymer obtained for the case H2O2/Fe2+ = 4 consisted of one part of lignosulfonate and five parts of poly(methyl methacrylate). The number of branches in the graft copolymer was 6 × 10−3/OCH3 or one every 167 guaiacyl nuclei.
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