Polymerization of epsilon-caprolactone initiated through powders of biological and nonbiological glasses

Eight biomedical glasses and three commercial ones, as finely divided powders, were tested as initiators for the ring-opening polymerization of epsilon-caprolactone, in bulk under vacuum at 185°C. All the glass powders were able to initiate the polymerization, along with Pyrex, which was totally inert towards the monomer as the inner surface of a phial. The obtained polymers were examined with FT-IR spectroscopy and atomic force microscopy. The molecular weights were measured by viscometry in chloroform. The presence of a fraction of the polymer firmly linked to the glass was quantitatively checked by the determination of the weight loss from the residues of the extraction with chloroform, after calcination in kiln at 945°C. The molecular weights and weight losses per unit surface were elaborated mathematically, so that a possible correlation between these properties and the atomic composition of the glasses could be better investigated. Two possible initiation mechanisms, induced by the hydroxyls present on the glass surface, were proposed: one for free poly(epsilon-caprolactone) and one for poly(epsilon-caprolactone) linked to the glass.