biodegradable poly are synthesized from amino acids , diols and dicarboxylic acids where one or both of the diols and dicarboxylic acids contain unsaturation ; e . g ., from di - p - nitrophenyl dicarboxylates and p - toluenesulfonic acid salts of bis disesters of diols where one or both of the dicarboxylate and diol moieties contain unsaturation or from di - p - nitrophenyl dicarboxylates , and p - toluene - sulfonic acid salts of bis diesters of diols and p - toluenesulfonic acid salt of lysine ester where one or both of the dicarboxylate and diol moieties contain unsaturation . the polymers are useful as biodegradable carriers for drugs of other bioactive agents .