MICROSPHERES BY DISPERSION POLYMERIZATION OF LACTIDES AND EPSILON-CAPROLACTONE

Polyester microspheres were synthesized by the ring-opening polymeriza tion of lactides (racemate or optically active L,L-isomer) and epsilon -caprolactone. Polymerizations were carried out in the 1,4-dioxane-hep tane mixed solvents in the presence of poly(dodecyl acrylate)-g-poly(e psilon-caprolactone) (poly(DA-CL)) used as surface-active agent. Polym erizations were initiated with tin(II) 2-ethylhexanoate (lactides), di ethylaluminum ethoxide or sodium trimethylsilanolate (epsilon-caprolac tone). In the studies of the polymerization of lactides, relations wer e determined between diameters, the distribution of diameters of synth esized microspheres, and the structure of poly(DA-CL). It was found th at it is possible, depending on thermal treatment of microspheres afte r synthesis, to obtain polylactide microspheres differing in the degre e of crystallinity. Kinetics of the dispersion pseudoanionic and anion ic polymerizations of epsilon-caprolactone were also investigated and the results of these studies were compared with the data for the corre sponding polymerizations of epsilon-caprolactone in solution.