Molecular mobility in amorphous biobased copolyesters obtained with 2,5-and 2,4-furandicarboxylate acid
Molecular mobility in amorphous biobased copolyesters obtained with 2,5-and 2,4-furandicarboxylate acid
复制标题
DOI：
10.1016/j.polymer.2020.123225
复制
发表时间：
2021-01-10
期刊：
影响因子：
4.6
通讯作者：
Dargent, Eric
中科院分区：
文献类型：
--
作者：
Bourdet, Aurelie;Araujo, Steven;Dargent, Eric
聚（2，5-呋喃二甲酸乙二醇酯）（2，5-PEF）是聚对苯二甲酸乙二醇酯（PET）最可靠的生物基替代品之一。导致呋喃二甲酸（FDCA）的汉克尔缩合反应提供三种位置异构体：2，5-FDCA（以最高产率获得）、2，4-FDCA（迄今为止被认为是副产物）和3，4-FDCA（痕量）。FDCA的两种主要异构体与二醇（例如乙二醇（EG））的共聚是获得具有调整的物理性质的一类呋喃基生物聚合物的令人感兴趣的方法。这项工作研究了用EG获得的三种共聚物的分子流动性以及2，5-FDCA和2，4-FDCA的比例，确保结晶完全破坏（90：10、85：15和50：50mol%2，5：2，4 FDCA），与均聚物2，5-PEF和2，4-PEF相比。通过交叉比较由调制温度差示扫描量热法（MT-DSC）、介电弛豫光谱（DRS）和热刺激去极化电流（TSDC）获得的结果来研究分子迁移率，目的是评估局部和链段分子迁移率、它们的活化能、以及弛豫时间和玻璃化转变时协同重排区域的温度依赖性。与对苯二甲酸（PET）中的苯环相比，2，5-FDCA（2，5-PEF）中的呋喃环具有较不线性的旋转轴，这对环翻转机制产生影响。2，5-FDCA和2，4-FDCA的不同之处在于呋喃环上羰基的位置，这增加了非线性的不对称性。将2，4-FDCA基单元引入到主要由2，5-FDCA基重复单元构成的聚合物主链中导致与局部松弛过程相关的较长松弛时间，对动力学脆性指数m没有显著影响，对协同性没有明显影响（在液态下观察到协同长度略有增加），对液态下链段α弛豫的活化能没有影响，和玻璃态活化能的降低。
Poly(ethylene 2,5-furandicarboxylate) (2,5-PEF) is one of the most credible biobased alternative to poly (ethylene terephthalate) (PET). The Henkel disproportionation reaction that leads to furandicarboxylic acid (FDCA) provides three position isomers: 2,5-FDCA (obtained with the highest yield), 2,4-FDCA (so far considered as a by-product), and 3,4-FDCA (traces). The copolymerization of the two main isomers of FDCA with a diol, e.g. ethylene glycol (EG), is an interesting approach to obtain a family of furan-based biopolymers with adjusted physical properties. This work investigates the molecular mobility of three copolymers obtained with EG and ratios of 2,5-FDCA and 2,4-FDCA ensuring the complete disruption of crystallization (90:10, 85:15 and 50:50 mol % of 2,5:2,4 FDCA), as compared to the homopolymers 2,5-PEF and 2,4-PEF. The molecular mobility was investigated by cross-comparing the results obtained by Modulated-Temperature Differential Scanning Calorimetry (MT-DSC), Dielectric Relaxation Spectroscopy (DRS) and Thermo-Stimulated Depolarization Currents (TSDC), with the aim of evaluating the local and segmental molecular mobilities, their activation energies, as well as the temperature dependence of the relaxation time and of the cooperatively rearranging regions at the glass transition. The furan ring in 2,5-FDCA (2,5-PEF) has a rotation axis that is less linear compared to the benzene ring in terephthalic acid (PET), with consequences on the ring-flipping mechanisms. 2,5-FDCA and 2,4-FDCA differ by the position of the carbonyl groups on the furan ring, which adds asymmetry to non-linearity. The incorporation of 2,4-FDCA-based units into a polymer backbone mainly constituted of 2,5-FDCA-based repeating units is responsible for longer relaxation times associated with the local relaxation processes, no striking effects on the kinetic fragility index m, no obvious effects on cooperativity (a slightly increase in the cooperativity length is observed in the liquid state), no effects on the activation energy for the segmental a relaxation in the liquid state, and a decrease in the activation energy in the glassy state.