Stereoselective zwitterionic ring-opening polymerization of rac-lactide. (10th October 2018)

• Record Type: Journal Article
• Authors: Si, Guifu; Zhang, Shaojie; Pang, Wenmin; Wang, Fuzhou; Tan, Chen
• Is Part Of: Polymer. Volume 154(2018)
• Page Start: 148
• Page End: 152
• Publication Date: 2018-10-10
• Subjects: Stereoselective -- Zwitterionic ring-opening polymerization -- N-Heterocyclic carbene; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2018.09.004
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: Stereoselective zwitterionic ring-opening polymerization (ZROP) poses a potentially great challenge in polymer chemistry because of its unique ion-pairing catalysis mechanism. Herein, a stereoselective ZROP of rac -lactide ( rac -LA) was explored for synthesis of isotactic cyclic polylactides by using commercially available N -heterocyclic carbene (NHC) catalysts at low temperature in tetrahydrofuran. The epimerization of lactide during ZROP can be inhibited at low temperature. The best isoselectivity can reach to a high value of P m = 0.91 associated with a high melting point ( T m ) of 193 °C. The resulting polylactides exhibit narrow molecular weight distributions ( M w / M n < 1.2) and inhibited transesterification as evidenced by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The resulting polylactide is predominantly cyclic as evidenced by 1 H NMR and MALDI-TOF MS analyses. Graphical abstract: Highlights: A stereoselective ZROP of rac -lactide generates isotactic cyclic polylactides. Commercially available NHCs result in cyclic polylactides with narrow molecular weight distributions ( M w / M n < 1.2). The best isoselectivity can reach to a high value of P m = 0.91. The resulting polylactide is predominantly cyclic as evidenced by 1 H NMR and MALDI-TOF MS analyses.