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 investigate their stability in aqueous media. The polymers are poly[bis-(ethyl glycolato)phosphazene],poly[bis(ethyl lactato)phosphazene],poly[bis(benzyl glycolato)phosphazene], and poly[bis(benzyl lactato)phosphazene]. The benzyl esters of glycolic and lactic acid were prepared by the base-catalyzed transesterification of their ethyl esters with benzyl alcohol at 90 degrees C. Poly(dichlorophosphazene) was treated with a large excess of the appropriate sodium acid ester at 50 degrees C to yield the fully-substituted polymer. To avoid unwanted molecular weight decline, these polymers were stored-under nitrogen or in vacuum. Hydrolytic 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.