Graft polymerization of methacrylate onto wool using dimethylaniline–benzyl chloride mixture as initiator



Graft polymerization of wool with methyl methacrylate (MMA) initiated by a dimethylaniline–benzyl chloride (DMA/BC) mixture was extensively studied. The grafting and homopolymerization reactions are influenced by the nature of the solvent used; ethanol proved to be the best. Using water as a cosolvent enhances significantly both graft formation and homopolymerization. A mixture of water/ethanol at a ratio of 90:10 constitutes the optimal medium for the grafting reaction. Addition of acetic acid or formic acid in low concentration (0.2 mole/l.) favors grafting. The opposite holds true for sulfuric and hydrochloric acid. Kinetic investigations showed that the rates of total conversion (Rp) and grafting (Rp′) are dependent of the concentrations of DMA, BC, acetic acid (Ac) and amount of wool (W), as well as temperature. They can be expressed by the following equations:

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The overall activation energies for the total conversion and grafting reactions amount to 8.5 and 9.0 kcal/mole, respectively; whereas the corresponding energies for initiations Ed are Ed′ 7.0 and 8.0 kcal/mole, respectively. The changes in the physical and/or chemical structure of wool via reduction, acetylation, and dinitrophenylation are reflected on the susceptibility of wool toward grafting. While reduced wool showed higher grafting, the graft yields obtained with acetylated and dinitrophenylated wools were quite poor. The alkali solubility of wool graft copolymer was determined and its tendency to felt was examined. Evidences for grafting were provided and a tentative mechanism for grafting initiation was suggested.