"Nonstrained" γ-Butyrolactone-Based Copolyesters: Copolymerization Characteristics and Composition-Dependent (Thermal, Eutectic, Cocrystallization, and Degradation) Properties
"Nonstrained" γ-Butyrolactone-Based Copolyesters: Copolymerization Characteristics and Composition-Dependent (Thermal, Eutectic, Cocrystallization, and Degradation) Properties
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DOI：
10.1021/acs.macromol.7b02174
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发表时间：
2017-11-14
期刊：
影响因子：
5.5
通讯作者：
Chen, Eugene Y. -X.
中科院分区：
文献类型：
--
作者：
Hong, Miao;Tang, Xiaoyan;Chen, Eugene Y. -X.
尽管生物衍生的γ-丁内酯（γ-BL）作为调节其共聚酯的材料性质的有效共聚单体具有几个预期的优点，但由于对高度稳定的（通常称为“非应变的”）γ-BL的开环聚合不利的热力学，目前未满足的挑战阻碍了获得具有高γ-BL结晶度的此类共聚酯。在这里，我们报告了有效的共聚γ-BL与两种常见的环状酯具有非常不同的单体热力学聚合性，ε-己内酯（ε-CL）和δ-戊内酯（delta-VL），导致一系列相对高的分子量（M-n高达135 kg/mol）无规共聚酯，具有前所未有的γ-BL结晶水平（高达84.0摩尔%），从而提供了在整个组成范围内的基于γ-BL的共聚酯，所述组成范围是对所得共聚酯的组成依赖性物理性质和降解行为进行全面研究所需的。这种共聚是通过明智地选择的金属和有机催化剂，表现出不同的动力学行为或单体选择性，旨在更有效地竞争的“非应变”γ-BL对相对高应变内酯开环。具有>50摩尔%的高γ-BL结晶度的共聚酯的成功合成导致发现γ-BL/ε-CL共聚物的低共熔相，其低共熔温度T-eu为11.0 ℃，低共熔组成X-eu为66.0% γ-BL;因此在该组成下，尽管两种组分均聚物是半结晶固体，但共聚物在室温下变成粘性液体。γ-BL基共聚酯的其他重要的组成依赖性的性质，包括热转变，共结晶，以及热和水解降解行为，也进行了研究。
Despite several anticipated advantages of the bioderived gamma-butyrolactone (gamma-BL) as an effective comonomer to modulate materials properties of its copolyesters, the currently unmet challenge hinders access to such copolyesters with high gamma-BL incorporations due to unfavorable thermodynamics toward the ring-opening polymerization of the highly stable, typically referred to as "nonstrained", gamma-BL. Here we report the effective copolymerization of gamma-BL with two common cyclic esters with very different monomer thermodynamic polymerizability, epsilon-caprolactone (epsilon-CL) and delta-valerolactone (delta-VL), leading to a series of relatively high molecular weight (M-n up to 135 kg/mol) random copolyesters with unprecedented levels of gamma-BL incorporations (up to 84.0 mol %) and thus providing access to gamma-BL-based copolyesters in the entire composition range needed for comprehensive investigations into the composition-dependent physical properties and degradation behavior of the resulting copolyesters. This copolymerization was enabled by the judiciously chosen metal and organic catalysts that exhibit different kinetic behavior or monomer selectivity, designed to more effectively compete the "nonstrained" gamma-BL against the relatively high-strained lactones toward ring-opening. The successful synthesis of the copolyesters with high gamma-BL incorporations of >50 mol % led to the discovery of the eutectic phase of the gamma-BL/epsilon-CL copolymer with a eutectic temperature T-eu of 11.0 degrees C and a eutectic composition X-eu of 66.0% gamma-BL; thus, at this composition, the copolymer becomes a viscous liquid at room temperature, although the two constituent homopolymers are semicrystalline solids. Other important composition-dependent properties of gamma-BL-based copolyesters, including thermal transitions, cocrystallization, as well as thermal and hydrolytic degradation behaviors, have also been examined.