Transition Metal Catalyst-free Room-temperature Polymerizations Based On Elemental Sulfur

Elemental sulfur,as the third richest element in fossil fuels,is abundant and cheap.Because the production of sulfur is much larger than its consumption,serious safety/environmental problems are caused during large scale sulfur storage.Hence,the direct utilization of sulfur has been a global concern.The reported utilization of sulfur in polymer synthesis generally require high temperature?above 180 ^oC?,and the resulting polymers usually have poor solubility and irregular structures.In recent years,multicomponent polymerizations?MCPs?have received much attention from polymer scientists due to its advantages such as mild conditions,simple operation,efficiency,high atom economy,and diverse structures.Therefore,developing economical,environment-friendly,convenient and efficient strategies of MCPs to solve the problem of sulfur utilization,and convert elemental sulfur directly to functional polymers not only have academic significance,but also have important industrial implication.Firstly,we prepared a library of polythioureas with elemental sulfur and reactive isocyanides,aliphatic amines through a catalyst-free room temperature multicomponent polymerization.This polymerization can be finished in 10 min at 100 ^oC or in 2 h at room temperature,suggested by the real-time monitor of in situ IR spectra,affording polythioureas with high M_ws?up to 242 500 g/mol?and excellent yields?up to 95%?.With the existence of the large number of thiourea groups,the polymers can be utilized to detect mercury pollution with high sensitivity?0.1 ppm?and high selectivity,which can clean Hg²⁺with high removal efficiency?99.99%?to achieve drinking water standard with a single treatment and can realize real-time monitoring of the removal process by fluorescence.Secondly,a polymerization of elemental sulfur and activated alkynes is developed to synthesize a series of conjugated polythiophenes.This polymerization can be finished in 30 min in the presence of KOH.The polymerization result obtained at room temperature is comparable to that obtained at 80 ^oC,and high M_ws?up to 51 800 g/mol?and excellent yields?up to 92%?can be achieved.Through monomer design,polythiophenes with mainchain located at 3,4-position or 2,5-position of thiophene ring can be obtained via this polymerization.In addition,the prepared conjugated polythiophenes enjoy great thermal stability?up to 480 ^oC when losing5 wt%?and high refractive index?n up to 1.7250?.In this thesis,we report the direct utilization of elemental sulfur in the preparation of functional polymers at room temperature without the catalysis of transition metal catalyst or without any catalyst.The development of sulfur-based polymerization not only provides a solution regarding to the sulfur hoarding problem,but also accelerates the development of sulfur-containing functional polymer materials,which kills two birds with one stone.