Vinyl Ester Polymers Containing Ibuprofen Pendant Groups: Synthesis, Characterization, and Evaluation

Vinyl ester polymeric systems linked to ibuprofen were synthesized and evaluated as materials for drug delivery. The carboxyl group of ibuprofen was converted into vinyl ester group by reacting ibuprofen with vinyl acetate in the presence of mercuric acetate as a catalyst. The resultant ibuprofen derivative of vinyl ester was then copolymerized with 2-hydroxyethyl methacrylate or methyl methacrylate (in 1:3 mole ratios) by utilizing azoisobutyronitrile as an initiator at the temperature range of 65-70ºC. The structure of all compounds was characterized and confirmed by FTIR, 1H NMR, and 13C NMR spectroscopy techniques and elemental analysis. Gel permeation chromatography was used for determination of the average molecular weights and polydispersity indices of the ibuprofen containing polymers. The hydrolysis of drugpolymer conjugates was carried out in cellophane membrane dialysis bags containing aqueous buffer solutions (pH 1, 7.4, and 10) at 37ºC for 48 h. Detection of hydrolysis solutions by UV-vis spectroscopy at selected intervals showed that the drug could be released by hydrolysis of the ester bonds which were formed between the drug and polymer backbone. The release profiles indicated that the hydrolytic behaviour of polymeric prodrugs is strongly based on polymer hydrophilicity and pH of the hydrolysis solution. The results suggest that these prepared polymeric prodrugs could be useful for release of ibuprofen in controlled release systems.