Ternary Catalyst System For Terpolymerization Of Lactide,Epoxides And Carbon Dioxide

In past decades,numerous remarkable works in the preparation of biodegradable polymers have been developed.These biomaterials could be applied as diposable products,biomedical material,packaging,optial materials and other applications.To create a sustainable society,these biomaterials are nessecary for their biodegradability in response to the growing “white pollution” around the world.For example,poly(lactic acid)(PLA)is a widely applied biopolymer,which originate from natual scource.PLA is synthesized via ring-opening polymerization(ROP)of lactide(LA).As a biocompatible thermoplastic,PLA could be used as packaging,bioplastic,container and biomedical material.However,the inherent brittleness,high price,poor gas barrier properties and other drawbacks prevented PLA to be widely applied.By contrast,Poly(propylene carbonate)(PPC)is produced by ring-opening copolymerization(co ROP)of CO2 and propylene oxide(PO),which utilizating the greenhouse gas carbon dioxide as C1 course.Contrast to PLA,PPC is of low cost,excellent light property,good oxygen barrier property and toughness.The glass transition temperature(Tg)of PPC(35-40 oC)is rather low,and PLA shows a higher Tg of 55 oC.Since PLA and PPC have complementary properties,producing PLA and PPC blends are captivating and promising.The copolymers with mixed properties are expected to meet virous demands in commercial fields.Though a few of catalysts fit both the ROP and co ROP processes,the synthesis of hybrid biopolymers is a chanllenge work.To efficiently catalyze the terpolymerization of epoxide,CO2 and lactide,we designed a series of ternary catalyst systems.With these ternary catalyst systems,we finally synthesized the terpolymers with multiblock structures.i.The ternary catalyst system?(TCS ?)comprises Salen Co?,Salen Co?,and Bis-(triphenylphosphino)-iminium chloride(PPNCl).Salen Co? is well-known catalyst for catalyzing co ROP of epoxides and CO2,we found that it could also catalyze the ROP of LA.However,the attempts of catalyzing ROP of LA and co ROP of epoxides/CO2 simutaneously failed by employing Salen Co? and PPNCl.Adding Salen Co? as the second active metal center is meaningful,which could cooperate with Salen Co? to catalyze the terpolymerization of LA,PO and CO2.The resultant terpolymer is confirmed as a multiblock copolymer,and of 100% polyester structure by 1D and 2D NMR spectra.Since no polyether is found,we predict that the terpolymer(PLLAPC)is completely biodegradable.We have also successfully applied TCS ? for other epoxids,such as cyclohexene oxide(CHO)and styrene oxide(SO).ii.TCS ? comprises Salen Co-DNP,Salen Co-DFTP and PPNCl.Salen Co-DFTP is specially designed for LLA,PO and CO2 terpolymerization.Salen Co-DFTP has different catalytic property than that of Salen Co-DNP.We employed Salen Co-DFTP instead of Salen Co? to creat a new ternary catalyst system.TCS ? is more active than TCS ? in catalyzing terpolymerization of LLA,PO and CO2,and obtaining a PLLAPC copolymer with higher molecular weight.iii.The ternary catalyst system could consist of Salen Co?,PPNCl and another kind of cocatalyst,for example,oxygen.Oxygen could be employed as a cocatalyst with Salen Co? in epoxide and CO2 copolymerization.Oxygen and PPNCl would enable Salen Co? to possess two working states,which display different catalytic properties.By switching from the two working states,Salen Co? could catalyze ROP and co ROP simultaneously.iv.Zinc glutarate(Zn GA)is a cheap and innocuous commercial catalyst.Zn GA,Salen Co? and PPNCl may form a heterogeneous ternary catalyst system(TCS ?V).TCS ?V is highly active in LLA,PO and CO2 terpolymerization,providing multiblock terpolymer with molecular weight as high as 698,000.In the mechanism investigation,we proposed that the existence of competition and cooperation between Zn GA and Salen Co at the same time.The cooperation links ROP of LLA and co ROP of PO/CO2 as a whole,and the competition determine the structure and content ratio of resultant PLLAPC.