Composites between alumina and an ester-ether-ester bioresorbable copolymer

Composites between alumina and the bioresorbable poly(epsilon -caprolactone )-block-poly(oxyethylene) block-poly(epsilon -caprolactone) copolymer were obtained by reacting e-caprolactone with preformed polyethylene glycol), in the presence of ceramic alumina powder, at 185 degreesC under vacuum. The mechanical properties, tested by compression and flexural strengths and You ng's modulus, show that the copolymer interacts poorly with the alumina gra ins. Both scanning electron and atomic force microscopy show a scarce wetta bility between alumina and copolymer, as well as the aggregation of alumina micro-particles into clusters of big size. Both mechanical lid morphologic al tests seem to indicate a stronger interaction between the alumina micro- particles than between the alumina. surface and the reaction mixture during the polymerization, as well as a "compacting effect" by alumina on the for ming copolymer. The FT-IR spectra of the,composites show both copolymer and alumina absorption bands The FT-IR analysis on the fractions of an extract ion with CHCl3 indicates the presence of traces of poly(epsilon -caprolacto ne), stably linked to alumina. The polymerization of epsilon -caprolactone with alumina alone in the same conditions gives poly(epsilon -caprolactone) , mainly free and in minor part linked to the alumina surface. Two polymeri zation mechanisms, simultaneously occurring, are proposed The most relevant result of this work is the lack of chemical inertness of alumina towards e psilon -caprolactone, which leads to reconsider also the use of alumina as a biochemically inert material.