含1,3,4-噻二唑环聚合物的合成及应用研究进展

含1,3,4-噻二唑环聚合物作为一类新型功能性的芳香杂环聚合物,由于其独特的储能性能、电催化活性、富电子特性而备受关注。近20年来对于含1,3,4-噻二唑环聚合物的研究从未间断,主要集中在材料的电化学合成和结构表征及其在可充电锂电池正极材料、生物化学传感器、临床诊断和药理学等领域的应用。电化学合成的方法有利于制备厚度可控的自支撑膜和对电极进行修饰,缺陷是造成电解液污染、成本高以及不适合规模化生产。研究者们尝试使用化学氧化聚合的方法来合成含1,3,4-噻二唑环聚合物,但除了2,5-二巯基-1,3,4-噻二唑聚合物可通过此方法成功合成外,主要得到的是一些配合物或配位聚合物。采用绿色的规模化的制备工艺来合成含1,3,4-噻二唑环聚合物是大势所趋。含1,3,4-噻二唑环聚合物的结构表征由于受到溶解性的限制,表征手段主要为X射线光电子能谱和红外(拉曼)光谱。2,5-二巯基-1,3,4-噻二唑聚合物由于具有高能量密度和高比容量而在二次锂电池正极材料的应用方面受到研究者们的青睐,但存在着充放电缓慢和电容量衰减快等缺陷。基于含1,3,4-噻二唑环聚合物修饰电极构建的传感器可高灵敏且高选择性地探测许多生物相关分子,但电极的稳定性有待改善。在所有的1,3,4-噻二唑环聚合物中,聚2-氨基-1,3,4-噻二唑(PAT)、聚5-氨基-1,3,4-噻二唑-2-硫醇或5-氨基-2-巯基-1,3,4-噻二唑(PAMT)以及聚2,5-二巯基-1,3,4-噻二唑(PBT)已通过电化学方法合成;PBT也在绿色的合成条件下采用化学氧化合成法合成得到,为其他1,3,4-噻二唑环聚合物的合成提供了借鉴,本课题组也通过化学氧化聚合法制备了PAT、PAMT和聚2-巯基-1,3,4-噻二唑(PTT)三类聚合物。目前,PBT作为二次锂电池正极材料研究得最多,其理论比容量高达362mAh/g,研究者们将PBT与聚吡咯、聚苯胺或水溶性磺化石墨烯等导电聚合物制成复合电极,进一步提高比容量和电极的稳定性并且加速充放电过程。基于含1,3,4-噻二唑环聚合物修饰电极构建的传感器在探测天然产物有效成分的含量、人和哺乳动物血液和体液或药品注射液中药物或代谢产物的含量、中药材或食品中的农药残留量以及水溶液中的重金属离子含量等方面取得了丰硕的成果;而将1,3,4-噻二唑环聚合物与全氟磺酸粘合剂、多壁碳纳米管复合可减少聚合物流失,从而起到增强电极稳定性和延长使用寿命的作用。本文归纳了1,3,4-噻二唑环聚合物研究进展,分别对1,3,4-噻二唑环聚合物的合成、结构表征途径及其应用等进行了介绍,分析了1,3,4-噻二唑环聚合物的研究中面临的问题并展望了其应用前景,以期为1,3,4-噻二唑环聚合物的制备工艺和功能拓展提供参考。

Advances in the Synthesis and Application of 1,3,4-ThiadiazoleRing-containing Polymers

As a new type of functional aromatic heterocyclic polymers,1,3,4-thiadiazole ring-containing polymers have attrac-ted a great deal of attention in recent years due to their unique energy storage,electrocatalytic activity and electron-rich properties.In the past two decades,the uninterrupted research over 1,3,4-thiadiazole ring-containing polymers has been mainly focused on the elec-trochemical synthesis and structural characterization of these polymers as well as their applications in cathode materials for rechar-geable lithium batteries,biochemical sensors,clinical diagnosis and pharmacology and other related fields. Electrochemical synthesis method is favorable to the preparation of self-supporting membrane with controllable thickness and easy modification for electrodes,but nevertheless presents many defects such as electrolyte contamination,high cost and unsuitability for large-scale production.Some researchers have made attempts to synthesize 1,3,4-thiadiazole ring-containing polymers via chemi-cal oxidative polymerization,though merely obtained some complexes or coordination polymers except 2,5-dimercapto-1,3,4-thia-diazole polymers,yet the environmental friendly and large-scale synthesis methodology represent the general trend.There are scanty means available for the structural characterization of 1,3,4-thiadiazole ring-containing polymers because of the solubility limitation, and the main characterization methods are X-ray photoelectron spectroscopy and infrared or Raman spectroscopy.The features of high energy density and high specific capacity have recommended 2,5-dimercapto-1,3,4-thiadiazole polymers to global researchers in see-king for the secondary lithium battery cathode materials,but they also suffer some weaknesses such as slow charge-discharge rate and rapid decline in the capacitance.Besides,the sensors constructed based on 1,3,4-thiadiazole ring-containing polymer modified electrodes have displayed potential for highly sensitive and highly selective detection of a rich variety of bio-related molecules,but the stability of these electrodes needs improvement. Among all 1,3,4-thiadiazole ring-containing polymers,poly-2-amino-1,3,4-thiadiazole (PAT),poly-5-amino-1,3,4-thiadiazole-2-thiol or poly-5-amino-2-mercapto-1,3,4-thiadiazole (PAMT)and poly-2,5-dimercapto-1,3,4-thiadiazole (PBT)have been synthe-sized through electrochemical method,while PBT has also been synthesized via a chemical oxidative synthesis method under green conditions,offering a reference for the synthesis of other 1,3,4-thiadiazole ring-containing polymers.Furthermore,our group also has successfully synthesized PAT,PAMT and poly-2-mercapto-1,3,4-thiadiazole (PTT)through chemical oxidative polymerization. So far,with respect to cathode material for secondary lithium ion battery,the PBT with a theoretical specific capacity of up to 362 mAh/g has been the most studied.Researchers have combined PBT with conductive polymers such as polypyrrole,polyaniline or wa-ter-soluble sulfonated graphene to further enhance the specific capacity and the stability of the electrode and accelerate the charge-dis-charge process.Meanwhile impressive strides have been made in fabricating the biochemical sensors based on 1,3,4-thiadiazole ring-containing polymers modified electrodes for the purpose of detection and content measurement of active ingredients in natural pro-ducts,drugs or metabolites in blood and body fluids of human/mammals or in the drug injections,the pesticide residues in Chinese herbal medicine or food,and heavy metal ions in aqueous solutions.Combining 1,3,4-thiadiazole ring-containing polymer with perf-luorosulfonic acid binder and multi-walled carbon nanotubes would facilitate to reduce polymer loss,thus enhancing the stability of the electrode and prolonging the service life. This review mainly concerns the worldwide research over 1,3,4-thiadiazole ring-containing polymers.It introduces the synthe-sis,structure characterization and application of 1,3,4-thiadiazole ring-containing polymers,and discusses the problems confronting the 1,3,4-thiadiazole ring-containing polymers and their application prospects.It is expected to provide a reference for the preparation technology and function extension of this species of polymers.