In this study, we experimentally and theoretically investigated the use of the symmetrical cyclic trifunctional initiator diethyl ketone triperoxide (DEKTP) in the bulk polymerization of styrene. The experimental study consisted of a series of isothermal batch polymerizations at different temperatures (120 and 130 C) with different initiator concentrations (0.005, 0.01, and 0.02 mol/L). A mathematical model was developed to predict the evolution of the reacting chemical species and the produced molecular weight distributions. The kinetic model included chemical and thermal initiation, propagation, transfer to the monomer, termination by combination, and reinitiation reactions. The simulation results predict the concentration of diradicals, monoradicals, and polymeric chains, characterized by the number of undecomposed peroxide groups. The experimental results showed that at reaction temperatures of 120-130 C, initiation by DEKTP produced an increase in the polymerization rates (R p 's) and average molecular weights, depending on the initiator concentration, due to sequential decomposition. The mathematical model was adjusted and validated with the experimental data. The theoretical predictions were in very good agreement with the experimental results. Also, an optimum initiator concentration was observed that achieved high R p 's and high molecular weights simultaneously. For polymerization temperatures of 120-130 C, the optimum concentration was 0.01 mol/L.
Oligomers of poly(vinyl alcohol) were grafted onto poly(3-hydroxybutyrate) (PHB) by radiation-induced polymerization. The aim of this study was to elucidate the structure of these copolymers using nuclear magnetic resonance (heteronuclear multiple quantum coherence) spectroscopy supported by dynamic light scattering (DLS) and atomic force microscopy (AFM). It was concluded that vinyl alcohol (VA) was grafted onto PHB for the methylenic and methynic sites. A mechanism for the grafting reaction was proposed based on the experimental evidence. AFM and DLS allowed the characterization of the particles obtained from P(HB-g-VA). The prepared materials showed suitable properties for use in drug delivery systems.
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