Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

Mark Abubekerov; Junnian Wei; Kevin R Swartz; Zhixin Xie; Qibing Pei; Paula L Diaconescu

doi:10.1039/c7sc04507g

Preparation of multiblock copolymers via step-wise addition of l-lactide and trimethylene carbonate

Chem Sci. 2018 Jan 11;9(8):2168-2178. doi: 10.1039/c7sc04507g. eCollection 2018 Feb 28.

Authors

Mark Abubekerov¹, Junnian Wei¹, Kevin R Swartz¹, Zhixin Xie², Qibing Pei², Paula L Diaconescu¹

Affiliations

¹ Department of Chemistry and Biochemistry , University of California , Los Angeles , CA 90095 , USA . Email: pld@chem.ucla.edu.
² Department of Materials Science and Engineering , University of California , Los Angeles , CA 90095 , USA.

Abstract

Poly(l-lactide) (PLA) is a bioderived and biodegradable polymer that has limited applications due to its hard and brittle nature. Incorporation of 1,3-trimethylene carbonate into PLA, in a block copolymer fashion, improves the mechanical properties, while retaining the biodegradability of the polymer, and broadens its range of applications. However, the preparation of 1,3-trimethylene carbonate (TMC)/l-lactide (LA) copolymers beyond diblock and triblock structures has not been reported, with explanations focusing mostly on thermodynamic reasons that impede the copolymerization of TMC after lactide. We discuss the preparation of multiblock copolymers via the ring opening polymerization (ROP) of LA and TMC, in a step-wise addition, by a ferrocene-chelating heteroscorpionate zinc complex, {[fc(PPh₂)(BH[(3,5-Me)₂pz]₂)]Zn(μ-OCH₂Ph)}₂ ([(fc^P,B)Zn(μ-OCH₂Ph)]₂, fc = 1,1'-ferrocenediyl, pz = pyrazole). The synthesis of up to pentablock copolymers, from various combinations of LA and TMC, was accomplished and the physical, thermal, and mechanical properties of the resulting copolymers evaluated.