Chebbi Yosra, Kasmi Nejib, Majdoub Mustapha, Papageorgiou George Z, Achilias Dimitris S, Bikiaris Dimitrios N
Laboratoire des Interfaces et Matériaux Avancés, Université de Monastir, Monastir 5000, Tunisia.
Laboratory of Polymer Chemistry and Technology, Department of Chemistry, Aristotle University of Thessaloniki, GR-541 24 Thessaloniki, Greece.
Polymers (Basel). 2019 Mar 6;11(3):438. doi: 10.3390/polym11030438.
In this study, the synthesis of poly(ethylene furanoate) (PEF), catalyzed by five different catalysts-antimony acetate (III) (Sb Ac), zirconium (IV) isopropoxide isopropanal (Zr Is Ip), antimony (III) oxide (Sb Ox), zirconium (IV) 2,4-pentanedionate (Zr Pe) and germanium (IV) oxide (Ge Ox)-via an industrially common combination of melt polymerization and subsequent solid-state polymerization (SSP) is presented. In all reactions, proper amounts of 2,5-dimethylfuran-dicarboxylate (DMFD) and ethylene glycol (EG) in a molar ratio of DMFD/EG= 1/2 and 400 ppm of catalyst were used. Polyester samples were subjected to SSP procedure, under vacuum application, at different reaction times (1, 2, 3.5, and 5 h) and temperatures of 190, 200, and 205 °C. Carboxyl end-groups concentration (⁻COOH), intrinsic viscosity (IV), and thermal properties, via differential scanning calorimetry (DSC), were measured for all resultant polymers to study the effect of the used catalysts on the molecular weight increase of PEF during SSP process. As was expected, it was found that with increasing the SSP time and temperature, the intrinsic viscosity and the average molecular weight of PEF steadily increased. In contrast, the number of carboxyl end-groups content showed the opposite trend as intrinsic viscosity, that is, gradually decreasing during SSP time and temperature increase. It is worthy to note that thanks to the SSP process an obvious and continuous enhancement in the thermal properties of the prepared PEF samples was attained, in which their melting temperatures () and degree of crystallinity () increase progressively with increasing of reaction time and temperature. To predict the time evolution of polymers IV, as well as the hydroxyl and carboxyl content of PEF polyesters during the SSP, a simple kinetic model was developed. From both the theoretical simulation results and the experimental measurements, it was demonstrated that surely the Zr Is Ip catalyst shows the best catalytic characteristics compared to all other used catalysts herein, that is, leading in reducing-in a spectacular way-the activation energy of the involved both transesterification and esterification reactions during SSP.
在本研究中，介绍了通过工业上常见的熔融聚合和随后的固态聚合（SSP）相结合的方法，由五种不同的催化剂——醋酸锑（III）（Sb Ac）、异丙醇锆（IV）（Zr Is Ip）、氧化锑（III）（Sb Ox）、2,4-戊二酮锆（IV）（Zr Pe）和二氧化锗（IV）（Ge Ox）——催化合成聚（呋喃二甲酸乙二酯）（PEF）的过程。在所有反应中，使用了适量的2,5-二甲基呋喃二甲酸酯（DMFD）和乙二醇（EG），其摩尔比为DMFD/EG = 1/2，并加入400 ppm的催化剂。聚酯样品在真空条件下，于不同反应时间（1、2、3.5和5小时）以及190、200和205°C的温度下进行SSP程序。对所有所得聚合物测量了羧基端基浓度（⁻COOH）、特性粘度（IV）以及通过差示扫描量热法（DSC）测定的热性能，以研究所用催化剂对SSP过程中PEF分子量增加的影响。正如预期的那样，发现随着SSP时间和温度的增加，PEF的特性粘度和平均分子量稳步增加。相反，羧基端基含量的数量呈现出与特性粘度相反的趋势，即在SSP时间和温度增加过程中逐渐减少。值得注意的是，由于SSP过程，制备的PEF样品的热性能得到了明显且持续的提高，其中它们的熔点（）和结晶度（）随着反应时间和温度的增加而逐渐升高。为了预测聚合物IV以及SSP过程中PEF聚酯的羟基和羧基含量随时间的变化，建立了一个简单的动力学模型。从理论模拟结果和实验测量结果都表明，与本文中使用的所有其他催化剂相比，Zr Is Ip催化剂确实表现出最佳的催化特性，即在SSP过程中以显著的方式降低了酯交换和酯化反应的活化能。
