“Nonstrained” γ-Butyrolactone-Based Copolyesters: Copolymerization Characteristics and Composition-Dependent (Thermal, Eutectic, Cocrystallization, and Degradation) Properties

• DOI: 10.1021/acs.macromol.7b02174
• Publication Date: 2017-10-25T19:19:41Z
• Authors: Miao Hong; Xiaoyan Tang; Brian S. Newell; Eugene Y.-X. Chen
• Keywords: Comonomer; Degradation

Despite several anticipated advantages of the bioderived γ-butyrolactone (γ-BL) as an effective comonomer to modulate materials properties its copolyesters, currently unmet challenge hinders access such copolyesters with high γ-BL incorporations due unfavorable thermodynamics toward ring-opening polymerization highly stable, typically referred "nonstrained", γ-BL. Here we report copolymerization two common cyclic esters very different monomer thermodynamic polymerizability, ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL), leading a series relatively molecular weight (Mn up 135 kg/mol) random unprecedented levels (up 84.0 mol %) thus providing γ-BL-based in entire composition range needed for comprehensive investigations into composition-dependent physical degradation behavior resulting copolyesters. This was enabled by judiciously chosen metal organic catalysts that exhibit kinetic or selectivity, designed more effectively compete "nonstrained" against high-strained lactones ring-opening. The successful synthesis >50 % led discovery eutectic phase γ-BL/ε-CL copolymer temperature Teu 11.0 °C Xeu 66.0% γ-BL; thus, at this composition, becomes viscous liquid room temperature, although constituent homopolymers are semicrystalline solids. Other important including thermal transitions, cocrystallization, well hydrolytic behaviors, have also been examined.