Abstract
PAMAM (Polyamidoamine) dendrimer was synthesized on solid spherical silica gel through a series of alternate Michael addition and amidation reactions. In contrast to homogeneous phase synthesis, solid-phase synthesis enables easy and efficient separation of the desired PAMAM-silica solid from the reactant mixture. In our kinetics studies, a novel method of successfully utilizing an inert group, 3-(triethoxysilyl) propionitrile (TESPN) immobilized on silica prior to synthesis, provided a distinctive band for normalizing Drift IR spectra. A plausible reaction kinetic model was then proposed and simulation was done with IR spectra and TGA measurements. Both experimental and simulated data matched each other and this validated our proposed model in establishing the presence of 'cross-linking' and steric hindrance phenomena during the amidation and Michael addition reactions respectively, producing structural defects. It was found that lower density of amino groups reduced structural defects, thus improving synthesis. Hence, the reaction kinetics study in this report is instrumental to the optimization of dendrimer synthesis on solid phase.
