Preparation and characterization of new difunctional cationic radical initiator-montmorillonite hybrids

Three different radical azo-initiators, containing quaternary ammonium moieties, were synthesized from 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)] propionamide. These initiators were intercalated into the galleries of montmorillonite (MMT), via cationic exchange, in order to obtain the radical initiator-MMT hybrids. The azo-initiators have dual functions: modifying MMT to be organophilic, and initiating the polymerization of vinylic monomers. The sizes of the intercalated initiators in the clay galleries were closely related to the interlayer d-spacing of their corresponding initiator-MMT hybrid. The swelling of the initiator-MMT hybrids was also tested towards various polar and non-polar monomers. Based on the interlayer d-spacing, and the swelling of the hybrids, 2,2′-azobis{2-methyl-N-[2-acetoxy-(2-N,N,N-tributylammonium bromide) ethyl] propionamide}-MMT was found to be the best of the radical initiator-MMT hybrids tested, especially for the non-polar monomers.