Preparation and characterization of the poly(2-hydroxyethyl methacrylate)–salicylic acid conjugate

A new polymeric system containing hydrolysable ester bond linked to salicylic acid to be used for controlled drug release was synthesized. Poly(2-hydroxyethyl methacrylate) (PHEMA) functionalized with chloroacetate groups was obtained by the reaction between PHEMA and chloroacetyl chloride using the N,N-dimethylacetamide/5% lithium chloride system as a solvent and pyridine as a catalyst. The degree of substitution was calculated from the chlorine content and ranged from 32.2 to 98.1 mol.% depending on the ratio of chloroacetyl chloride to PHEMA. The coupling of salicylic acid to PHEMA functionalized with chloroacetate groups was carried out by the reaction between PHEMA and the sodium salt of salicylic acid. The structures of chloroacetylated PHEMA and PHEMA–salicylic acid conjugates were determined by means of FTIR, 1H-NMR and 13C-NMR spectra. The hydrolysis in the heterogeneous system of PHEMA–salicylic acid conjugates were performed in buffer solutions (pH 7.6 and 8.5) at 37 °C and showed that the release of the drug (sodium salicylate) from tablets was dependent on the hydrophilic character of conjugate as well as on the pH value of the medium.