SHORT METHYLENE SEGMENT CROSS-LINKS IN DEGRADABLE ALIPHATIC POLYANHYDRIDE - NETWORK FORMATION, CHARACTERIZATION, AND DEGRADATION

Crosslinked poly(adipic anhydride) has been obtained in this study of the synthesis of a rapidly hydrolyzable crosslinked polymer system. Th e thermal, mechanical, and degradative behavior was markedly affected by the ratio of reactants, using 0-50 mol % of the crosslinking agent. Optimum properties were reached at 20-30 mol %. Methylene segment cro sslinks were obtained by copolymerizing oxepan-2,7-dione (adipic anhyd ride) with 1,2,7,8-diepoxyoctane. The crosslinking reaction resulted i n polyester bonds but the material had a significant amount of poly(ad ipic anhydride) homosequences. These are crucial for a rapid degradati on. The network formation is dependent on the functionality of the rea ctants, on the reactivities of the functional groups and on the reacti on pathways. In this study, the most important factor affecting the st ructure of main chains is the higher reactivity of the anhydride compa red to that of the epoxide leading to homopolymer sequences. This was also evident in the model reaction between oxepan-2,7-dione and 1,2-ep oxybutane. The initial degradation profile of the crosslinked polymer corresponds to the linear counterpart of the polymer. The remaining po lyester network has a longer degradation rate. (C) 1996 John Wiley & S ons, Inc.