Synthesis and characterization of well-defined random and block copolymers of ε-caprolactone with l-lactide as an additive for toughening polylactide: Influence of the molecular architecture.

ABSTRACT Well-defined multiarmed star random and block copolymers of ε-caprolactone with l-lactide with controlled molecular weights, low polydispersities, and precise numbers of arms were synthesized by the ring-opening polymerization of respective cyclic ester monomers. The polymers were characterized by ¹H-NMR and ¹³C-NMR to determine their chemical composition, molecular structure, degree of randomness, and proof of block copolymer formation. Gel permeation chromatography was used to establish the degree of branching. Star-branched random copolymers exhibited lower glass-transition temperatures ( T_g's) compared to a linear random copolymer. When the star random copolymers were melt-blended with poly( l-lactic acid) (PLA), we observed that the elongation of the blend increased with the number of arms of the copolymer. Six-armed block copolymers, which exhibited higher T_g's, caused the maximum improvement in elongation. In all cases, improvements in the elongation were achieved with no loss of stiffness in the PLA blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43267. [ABSTRACT FROM AUTHOR]