Thermal characterization of polymer-silica composites loaded with ibuprofen sodium salt

The study describes the thermal properties of a series of porous microspheres synthesized with 2-hydroxyethyl methacrylate (HEMA) and trimethylolpropane trimethacrylate (TRIM), their conjugates with ibuprofen sodium salt (IBS) and finally the polymer-drug-silica composites based on them. The poly(HEMA-co-TRIM) and pure poly(TRIM) permanently porous microspheres were synthesized via suspension-emulsion polymerization. The polymer-drug conjugates were produced by introduction of the IBS into the polymer beads by their swelling. The polymer-drug-silica composites were synthesized by the hydrolysis and condensation of silica precursor (tetraethoxysilane, TEOS) introduced into the conjugates. The transformation of TEOS was performed in the vapor phase of the acidic (A) or basic (B) catalyst. The conducted TG/FTIR/MS studies reveal that the initial decomposition temperature for organic matrices was dependent on the amount of HEMA monomer. Moreover, the thermal properties of the composites differ significantly from the pure polymer matrices. After the introduction of the drug and silica gel into the polymeric beads, the thermal stability of the composite materials was enhanced in comparison with the parent matrices, even at about 40 degrees C. This result was attributed to the shielding effect of IBS molecules and silica particles. FTIR and QMS analysis of the gases evolved during degradation indicates that the depolymerization, alpha- and beta-hydrogen bond scission reactions went probably in parallel during the samples' thermal degradation. (C) 2015 Elsevier B.V. All rights reserved.