Ismael Casinos

Role of ceric ion in the heterogeneous graft polymerization of olefins on cellulose

Abstract The heterogeneous graft copolymerization of vinyl monomers on cellulose initiated by aqueous ceric ion is studied theoretically. Mechanistic aspects are considered. Some suggestions are made about: polymerization schemes; concerted disproportionation of cellulose-ceric ion complexes; oxidation sites in cellulose or cellulose sites of grafting (block and graft copolymer formation); reactivity of olefins towards cellulose radicals; reactivity of olefins in homopolymerization initiated by ceric ion; reactivity of radical chains in termination by ceric ion; estimation of reaction parameters (rate of graft copolymerization, rate of homopolymerization, rate of ceric ion consumption, grafting efficiency, molecular weight, number of polymer chains, grafting frequency and initiation efficiency) in terms of the reaction variables; and a polymerization scheme for electron-rich monomers. The effect of reaction variables on reaction parameters can be accounted for by equations developed in this paper. Consequently, some characteristics of the copolymers and copolymerization reactions can be understood. A way of demonstrating transitions between competitive reactions is developed.

Mechanisms for the radical graft polymerization of vinyl and/or acrylic monomers on cellulose

A model for the heterogeneous graft polymerization of vinyl and/or acrylic monomers on cellulose initiated by ceric ions is developed. The model can be easily extended to other (poly)hydroxylic substrates, other one-electron oxidants and homogeneous systems. Three component mechanisms are suggested to be relevant in a radical graft polymerization: from, onto and from-to. Several competitive reactions appear in the polymerization scheme that lead to related mechanistic cases. The electronic nature of the monomer and the number of polymerization sites are taken into account. Expressions for reaction parameters as a function of reaction variables are deduced. Some structural knowledge of the copolymer is derived from the model.