POLY (ORTHO ESTERS)

The synthesis and characterization of four distinct families of poly (ortho esters) are described and designated as poly (ortho esters) I, II, III and IV. Poly (ortho ester) I is prepared by the transesterification of diethoxytetrahydrofuran with diols. Poly (ortho ester) II is prepared by the condensation of 3,9-bis (ethylidene 2,4,8,10-tetraoxaspiro [5, 5] undecane) with diols to produce a linear polymer or with a triol to produce a crosslinked polymer. Poly (ortho ester) III is prepared by the condensation of a flexible triol with and alkyl orthoacetate to produce ointment-like materials. Poly (ortho ester) IV is prepared by the condensation of a rigid triol with and alkyl orthoacetate to produce solid materials. The detailed mechanism of hydrolysis of these polymers has been determined and drug release data for a number of therapeutic agents are presented.