title: Novel microwave-assisted synthesis of poly(D,L-lactide): the influence of monomer/initiator molar ratio on the product properties.
abstract: Poly(D,L-lactide) synthesis using tin(II) 2-ethylhexanoate initiated ring-opening polymerization (ROP) takes over 30 hours in bulk at 120 °C. The use of microwave makes the same bulk polymerization process with the same initiator much faster and energy saving, with a reaction time of about 30 minutes at 100 °C. Here, the poly(lactide) synthesis was done in a microwave reactor, using frequency of 2.45 GHz and maximal power of 150 W. The reaction temperature was controlled via infra-red system for in-bulk-measuring, and was maintained at 100 °C. Different molar ratios of monomer and initiator, [M]/[I], of 1,000, 5,000 and 10,000 were used. The achieved average molar masses for the obtained polymers (determined by gel permeation chromatography) were in the interval from 26,700 to 112,500 g/mol. The polydispersion index was from 2.436 to 3.425. For applicative purposes, the obtained material was purified during the procedure of microsphere preparation. Microspheres were obtained by spraying a fine fog of polymer (D,L-lactide) solution in tetrahydrofuran into the water solution of poly(vinyl alcohol) with intensive stirring.
authors.affiliation: Faculty of Technology, University of Nis, Bulevar oslobodjenja 124, 16000 Leskovac, Serbia. nljubisa@yahoo.com
authors.forename: Ljubisa
authors.initials: L
authors.lastname: Nikolic
authors.forename: Ivan
authors.initials: I
authors.lastname: Ristic
authors.forename: Borivoj
authors.initials: B
authors.lastname: Adnadjevic
authors.forename: Vesna
authors.initials: V
authors.lastname: Nikolic
authors.forename: Jelena
authors.initials: J
authors.lastname: Jovanovic
authors.forename: Mihajlo
authors.initials: M
authors.lastname: Stankovic