SYNTHESIS OF POLY(ORGANOPHOSPHAZENES) WITH GLYCOLIC ACID ESTER AND LACTIC-ACID ESTER SIDE-GROUPS - PROTOTYPES FOR NEW BIOERODIBLE POLYMERS

Four different poly(organophosphazenes) bearing esters of glycolic or lactic acid as side groups have been synthesized in order to investiga te their stability in aqueous media. The polymers are poly[bis-(ethyl glycolato)phosphazene],poly[bis(ethyl lactato)phosphazene],poly[bis(be nzyl glycolato)phosphazene], and poly[bis(benzyl lactato)phosphazene]. The benzyl esters of glycolic and lactic acid were prepared by the ba se-catalyzed transesterification of their ethyl esters with benzyl alc ohol at 90 degrees C. Poly(dichlorophosphazene) was treated with a lar ge excess of the appropriate sodium acid ester at 50 degrees C to yiel d the fully-substituted polymer. To avoid unwanted molecular weight de cline, these polymers were stored-under nitrogen or in vacuum. Hydroly tic decomposition profiles in aqueous media were monitored by P-31 NMR spectroscopy and by gel permeation chromatography (GPC). The possible utility of these polymers as biomedical materials is discussed.