The benzyl ester of the β-lactone of malic acid was synthesized from bromosuccinic acid and polymerized both in bulk and in solution by anionic and cationic initiators and by a heterogeneous catalyst. Anionic polymerization reactions yielded polymers with weight average molecular weights as high as 50,000 as determined by GPC, and with narrow molecular weight distributions. The benzyl ester polymers were readily converted to poly(malic acid) by hydrogenolysis without loss in molecular weight. Poly(malic acid) is being evaluated as a biodegradable, bioresorbable component in drug delivery systems, particularly as a non-toxic, slow release carrier for covalently bound drugs.
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