Poly(vinyl alcohol)-Salicylic Acid Conjugate: Synthesis and Characterization

The polymeric system containing hydrolysable ester bonds linked to salicylic acid was synthesized for controlled drug release. Poly(vinyl alcohol) (PVA) functionalized with chloroacetate groups was obtained by reaction of PVA with chloroacetyl chloride using the N,N-dimethylacetamide/5% lithium chloride system as solvent and pyridine as catalyst. The degree of substitution was calculated from the chloride content and ranged from 37.8 to 98.9 mol%. The coupling of salicylic acid to PVA functionalized with chloroacetate groups was carried out by the reaction with between PVA and the sodium salt of salicylic acid. The structures of chloroacetylated PVA and PVA-salicylic acid conjugates were determined by means FTIR, 1H-NMR and 13C-NMR spectra. The hydrolysis in the heterogeneous system of PVA-salicylic acid conjugates were performed in buffer solutions (pH 7.6 and 8.5) at 37℃. Detection of hydrolysis by UV spectroscopy showed that released the drug, can by achieved by the hydrolysis of the ester bond between the drug and the polymeric carrier. The release profiles indicated that the release of the drug (sodium salicylate) from tablets was dependent on hydrophilic character of conjugate and the pH of the buffer solution.