The Copolymerization Of Carbonyl Sulfide With Oxetane

The copolymerization of COS with oxetane(OX)was investigated comprehensively in this dissertation,including:(1)the catalytic synthesis of poly(trimethylene thiocarbonate)(PTMMTC);(2)the exploration of the effect of the extent of the oxygen-sulfur exchange reaction on the solubility and crystalline behaviors of the resultant PTMMTCs.Semicrystalline PTMMTC was successfully synthesized through the copolymerization of COS with OX using binary(salen)CrCl/base catalyst systems.There were some factors were studied,including the reaction temperature,the catalyst promotors,solvents,ligand types and axial ions,to figure out the effect on copolymerization of COS with OX.FT-IR and high temperature NMR spectra were used to identify the structure of PTMMTC.The initial decomposition temperature of PTMMTC was 228.5°C,determined by TGA.DSC and XRD were utilized to characterize the crystalline behavior of PTMMTC.The range of the melting point(Tm)of PTMMTC is from 110 to 125°C,and the range of corresponding melting enthalpy(△Hm)of PTMMTC is from 30 to 50 J/g.According to the XRD profile,two spiculate peaks were observed,2 theta(θ)s were 19.0 and 22.9°.The crystallinity of PTMMTC was calculated by Jade 6.5 and up to 71%according to the XRD profile.High temperature GPC was used to determine the number average molecular weight(Mn)and the polydispersity index(PDI)of PTMMTC.Mns were 4.9-55.7 kg/mol with PDI of 1.6-2.4.The solubility and the crystalline behaviors of the COS/OX copolymers were investigated by tuning the extent of the oxygen-sulfur exchange reaction(O-S ER).NMR and high temperature NMR were used to determine the structure of DCM-soluble and DCM-insoluble portion of the copolymer.As for the related factors to O-S ER,the reaction temperature and catalyst promotors were investigated to illustrate the impact of the extent of O-S ER on the microstructure of the resultant copolymers.The mass ratio of the DCM-soluble portion of the copolymer increased and its Tg declined with raising the reaction temperatures from 140 to 155℃,meanwhile the mass ratio of the DCM-insoluble portion of the copolymer decreased,Tm&Tg also descended.The structure producing by O-S ER and the solubility of the copolymers were affected by catalyst promotors,as well as the crystalline behaviors of the copolymers,including its Tg,Tm and △Hm.The solubility and the crystalline behaviors of the copolymers was strikingly affected by the extent of O-S ER.In conclusion,semicrystalline PTMMTC was successfully synthesized by copolymerizing of COS with OX employing binary(salen)CrCl/base catalyst systems,which broadens the types and the potential applications of polythiocarbonates.