Screening of metal catalysts influence on the synthesis,structure, properties,and biodegradation of PLA‐PBA triblock copolymers obtained in melt

The synthesis of ABA type triblock copolymers comprising poly(1,4‐butylene adipate) macroinitiator and polylactide segments is described in this article. Acetylacetonates of various low‐toxic metals: Li, Mg, Ca, Zn, Fe, and Zr are used as catalysts. The course of polymerization, microstructure, thermal properties, and biodegradation of the copolymers obtained are analyzed based on the electronegativity of the metal used. The macroinitiator is completely incorporated into the major products, however, linear and cyclic lactide homopolymers and copolymers are present because of moisture presence and transesterification processes. The efficiency of side reactions depends on the catalyst used. The highest molar mass of copolymer is obtained with a Zr‐based catalyst. The efficacy of polylactide racemization is higher for catalysts comprising the metal of lower electronegativity. Under thermal degradation conditions the polylactide segment degrades before the macroinitiator one. The copolymers studied undergo faster biodegradation than polylactide and they can decompose in compost within 16 weeks. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1444–1456