Study On The Synthesis Of Polythioester By Copolymerization Of Cyclic Thioanhydride And Episulfide

Polythioester refers to a class of polymers in which at least one oxygen atom of an ester unit in a polyester backbone is replaced with a sulfur atom.Compared to the corresponding polyesters,polythioesters exhibit more excellent thermodynamic and optical properties.At present,the preparation methods of polythioester mainly include polycondensation and ring-opening polymerization.However,the polycondensation method requires heating or decompression of the reaction system to separate the small molecules generated during the reaction,which is a high-energy-consuming process;The ring-opening polymerization method is limited by fewer kinds of monomers,the resulting polythioester structures and species are relatively simple.Based on the above problems,this dissertation has developed a method for preparing polythioesters by polymerization of thiirane and cyclic thioanhydrides.The following research work has been carried out focusing on the design of catalytic systems,the expansion of monomers,and the properties of polymers.1.A method for preparing an episulfide is developed.The thiirane was prepared using a reaction system consisting of neutral alumina and water.The conversion rate of various sulfananes within 3 h under mild conditions of water as a solvent,catalytic amount of neutral alumina,and 40 ~oC can reach over 94%.This method has the advantage of producing a large amount of sulphanes.It can be used to prepare chiral episulfide compounds.2.A two-component catalytic system based on metal chromium complexes has been developed to realize the alternating copolymerization of episulfide and thio anhydride.The catalytic activity,regioselectivity and reaction performance between different monomers were studied in detail.In this reaction,SalenCr(III)Cl/PPNCl exhibited higher reactivity and polymer selectivity.Electrospray-time-of-flight tandem mass spectrometry and ~1HNMR spectroscopy at different reaction times were used to demonstrate that the resulting polymer had a perfectly alternating copolymerization structure.The DSC chart shows that the polymer is a crystalline polymer with a melting point of 90 ~oC.The introduction of sulfur atoms allows the refractive index of the material of this type of polymer to reach 1.78(25 ~oC),which is significantly higher than that of similar structural polyester materials.The corresponding stereocomplexes were prepared,the melting point of which was increased to 166 ~oC,and the melting point of the polymer with a single optical configuration was only 92 ~oC.The powder X-ray diffraction test results showed that the stereocomplexes had different diffraction with the single optical configuration polymer peak.