Precise Synthesis Of Crystalline Sulfur-Containing Polymers

Sulfur-containing polymers are referred to the polymer containingat least one sulfur atom in the repeat unit in the main chain.The excellent properties,including ready polarizability,strong coordinating ability and the high atomic refraction,endow such kind polymers with excellent optical properties,thermal stability,chemical resistance and adhesion to heavy metals,etc.Hence,sulfur-containing polymers have much potential application in the area of optical components,optoelectronic,adhesives as well as thermal absorbing.As results,various sulfur containing polymers were developed,such as polythioether,polythioester,polythiocarbonates,polydisulfides and polysulfites,etc.However,the strong coordinating ability together with the multiple valence of the sulfur atom caused many problems when synthesizing these polymers,like uncontrolled molecular weight and dispersibility,mixed main chain sequence and the poor regio-and stereoselectivity.Therefore,the selective synthesis of well-defined sulfur-containing polymers with high molecular weight becomes a vital theme in this area.Moreover,the achievement that precisely synthesizing the sulfur-containing polymers with controlled stereochemistry and topological structure will be a more challenge work.In terms of these issues,we made an effort to precisely synthesizing sulfur-containing polymers via designing efficient catalysts,developing synthetic methodology,controlling the stereochemistry of the polymerization and the topological structure of resultant polymers.1.The regioselective copolymerization of COS with epichlorohydrin was achieved by employing Cr-based bifunctional catalyst,affording the isotactic polymonothiocarbonatewith chiral ECH as monomer.As explored,the crystalline behavior of the isotactic polymonothiocarbonate is greatly affected by the molecular weight.The polymonothiocarbonate with low molecular weight is amorphous though the isotactic nature,while the isotactic polymonothiocarbonate with high molecular weight is a semicrystalline polymer with a meltingtemperature(Tm)of 97?.2.The binaphthyle based dinuclear SalenCo(?)X(X is 2,4-dinitrophonate)complex was synthesized for the stereoselective copolymerization of COS with CHO.The(R,R,R,R,R)dinuclear Co(?)complex exhibited excellent stereoselectivity,providing the polymonothiocarbonate with the isotactivity of>99%.The thermal property and the wide angle X-ray diffraction revealed the crystalline nature of this isotactic polymonothicoarbonate.When copolymerizing COS with other meso-epoxides in the presence of this dinuclear Co(?),a series of crystalline isotactic polymothiocarbonates were synthesized with Tm up to 232?.DFT calculation was used for illustrating why the(R,R,R,R,R)-dinuclear Co(?)complex showed excellent stereoselective control of the asymmetric copolymerization of COS with mesoepoxides.Moreover,these polymonothiocarbonates possessed good optical properties,among which the Abbe number of COS/CXO copolymer reached up to 43 with the refractive index of 1.53,implying this kind polymers with good optical and thermal properties have the potential of being applied in the field of photoelectronicdevices.3.A facile strategy were developed for synthesizing branched polymonothiocarbonates via one-pot copolymerization of COS and epichlorohydrin using Cr-based bifunctional catalyst.the thermal stabil ity of the branched polymonothiocarbonate was enhanced with glass transition temperature(Tg)elevated by 22 ?,compared to the linear ones.When chiral ECH was used,the crystalline branched polymononthiocarbonate was accessible with the enhanced Tm by 30?.With this method,the lengths of the side chains are tunable by varying the reaction temperature.The newly developed strategy for branched polythiocarbonate not only enriched the topological sulfur-containing polymers diversity,but also extended the synthetic methodology for branched polymers.4.Copolymerization of ethylene oxide(EO)with COS was achieved in an efficient way,affording the polymonothiocarbonates with alternated structure and high molecular weight up to 193.3 kg/mol.The DSC test revealed the crystalline nature of this polymer with a Tm of 128?.Based on the living polymerization character of this copolymerization,in the presence of diol as chain transfer agent,the "hard-soft-hard" triblock polymonothiocarbonate,in which the COS/EO copolymer server as "hard" segment and COS/PO copolymer served as "soft"segment,was synthesized with the thermal elastomer character.5.An efficient method for synthesizing aliphatic polythioesters was developed by copolymerizing episulfides with cyclic thioanhydrides with organic ammonium salts as initiators.Being benefited from the ready accessible and diverse row material,the structures of the obtained polythioesters are multiple and tunable.The influences on the copolymerization rate produced by the cationic and anionic portion of the ammonium salts were explored by DFT calculation and in situ IR.The living polymerization character of this copolymerization provides the opportunity of synthesizing well-defined block polythioesters.Moreover,thermal property characterization revealed the good thermal stability of these polymers.Especially,the STA/PS copolymer exhibited crystalline nature with the Tm of 81?,which can be enhanced to 91? by employing(R)-PS.The optical property text showed the refractive index of this polymer reached 1.78,which is one of the highest values of the reported degradable sulfurcontaining polymers.The "metal free" strategy provide the potential for these poly(thioester)s to be utilized as high-performance engineering plastics,as well as optical,optoelectronic,and photochemical materials.