Modification of natural rubber:: A study by 1H NMR to assess the degree of graftization of polyDMAEMA or polyMMA onto rubber particles under latex form in the presence of a redox couple initiator

On the basis of the proposal that cumene hydroperoxide (CHP) in the presence of the base tetraethylenepentarnine (TEPA) can form radicals by the abstraction reaction over addition to allylic double bonds, the efficiency of grafting monomers of methyl methacrylate (MMA) and dimethylaminoethylmethacrylate (DMAEMA) on to natural rubber (NR) has been studied. Seeded emulsion polymerization was used to graft such monomers. Different concentrations of each monomer have been examined. The effects of the concentrations of the monomers were evaluated by H-1 NMR spectroscopy and Transmission Electron Microscopy (TEM). There is good evidence for the formation of graft copolymers of modified NR under the core-shell morphology as well as satisfactory efficiency of grafting in the presence of high concentrations of both monomers. At lower concentrations the grafting were not significant. The images of the morphology was obtained by Transmission Electron Microscopy after the preparation of the samples by cryo-sectioning and chemical fixation techniques. (c) 2005 Elsevier Ltd. All rights reserved.