Versatile and controlled synthesis of resorbable star-shaped polymers using a spirocyclic tin initiator-Reaction optimization and kinetics

• Published in: Journal of polymer science. Part A, Polymer chemistry Polymer chemistry, 2006-01, Vol.44 (1), p.596-605
• Main Authors: Odelius, Karin, Finne, Anna, Albertsson, Ann-Christine
• Format: Article
• Language: English
• Subjects: Applied sciences; Chemistry; Exact sciences and technology; Kemi; narrow molecular-weight distribution; NATURAL SCIENCES; NATURVETENSKAP; Organic chemistry; Organic polymers; Organisk kemi; Physicochemistry of polymers; poly(L-lactide); Polymer chemistry; Polymerization; polymerization kinetics; Polymerkemi; Preparation, kinetics, thermodynamics, mechanism and catalysts; spirocyclic tin initiator; star-shaped architecture
• ISSN: 0887-624X; 1099-0518; 1099-0518
• DOI: 10.1002/pola.21192

A spirocyclic tin initiator was synthesized from pentaerythritol ethoxylate and dibutyltin oxide and used to polymerize L‐lactide with dichloromethane, chloroform, toluene, and chlorobenzene as solvents. The reactions were performed at different temperatures and it is concluded that neither the temperature nor the solvent affects the molecular weight or the molecular weight distribution of the star‐shaped polymers. The reaction rate was significantly increased by raising the reaction temperature or choosing a solvent with a low dielectric constant. All polymers showed a molecular‐weight distribution below 1.19 and a molecular‐weight determined by the initial monomer to initiator concentration ([M]0/[I]). No induction period was seen for the polymerizations. They were all first order in initiator and the degree of aggregation in toluene at 110 °C was found to be 4/5. The glass transition temperature and the melting temperature of the star‐shaped polymers increase with increasing arm length. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 596–605, 2006 Well defined star‐shaped polyesters were synthesized using a spirocyclic tin initiator, where L‐lactide was chosen as a model system for the investigation of the polymerization kinetics. Dichloromethane, chloroform, toluene, and chlorobenzene were chosen as the solvents and used just below their boiling point and when possible also at 40, 60, 80, and 110 °C. It is concluded that neither the temperature nor the solvent affects the molecular weight or the molecular‐weight distribution of the star‐shaped polymers, which all show a molecular‐weight distribution below 1.19 and a molecular weight determined by the initial monomer to initiator concentration.