Study On The Selective Ring-opening Copolymerization Catalyzed By Zinc Glutarate

Nowadays,with the rapid development of the global economy,environmental problems can not be ignored,so degradable polymer materials emerge.Aliphatic polyester and polycarbonate,as biodegradable and biocompatible environment-friendly biomaterials,have been widely studied due to their excellent material properties and easy degradation.Ring opening polymerization（ROP）of cyclic lactone and ring opening copolymerization（ROCOP）of epoxides and cyclic anhydrides/carbon dioxide are very effective methods to synthesize aliphatic polyesters and polycarbonates with different structures and properties.At present,the chemo-selective polymerization of mixed monomers is a research hotspot,but the catalysts are mainly homogeneous metal catalysts and organic catalysts.Zinc glutarate（ZnGA）catalyst,as a heterogeneous catalyst,has attracted much attention due to its simple preparation method,easy post-treatment and low cost.Therefore,we used ZnGA as the catalyst for selective polymerization.1.Using ZnGA to catalyze the ring-opening polymerization（ROP）of L-lactide（LA）,the effects of reaction conditions on the polymerization were studied.The results showed that neither ZnGA nor propylene oxide（PO）alone could induce LA ROP,but the ZnGA/PO catalytic system showed good catalytic activity for LA ROP.Through the use of different initiators,epoxides（PO,ECH,CHO and AGE）and alcohols（CH₃OH）to explore the ROP reaction process of LA,it showed that both epoxides and alcohols can initiate LA ROP.Subsequently,the mechanism of the reaction was proposed,which proved that zinc alkoxide（-Zn-OR）intermediate was formed during the reaction.Finally,polylactides with controllable molecular weight and narrow molecular mass distribution（PDI<1.3）were prepared by ROP of LA using ZnGA as catalyst and PO as initiator.2.ZnGA was used to catalyze the chemo-selective polymerization of mixed monomers of propylene oxide（PO）,phthalic anhydride（PA）and L-lactide（LA）to prepare block polymers.The ring-opening copolymerization（ROCOP）of PO/PA and the ring-opening polymerization（ROP）of PO/LA were studied respectively.The optimal reaction conditions were discussed,and the kinetic characteristics of the polymerization process were analyzed（the insertion of PA followed the zero-order kinetic reaction,and the insertion of LA followed the first-order kinetic reaction）.After that,the one-pot method was used to catalyze the copolymerization of mixed monomers of PA,PO and LA and the block polymer was successfully prepared.¹H-NMR,¹³C-NMR,GPC and DOSY NMR proved the successful preparation of the obtained block polymer.The obtained block polymer had a molecular mass of 6.6kg/mol and PDI of 1.22.The reaction mechanism of the terpolymerization was studied,and the reaction mechanism of mixed monomer copolymerization was proposed.Finally,the universality of ZnGA-catalyzed selective copolymerization of mixed monomers was studied by changing the types of epoxides（ECH,CHO and AGE）and cyclic anhydrides（SA and NA）respectively.3.Use ZnGA to catalyze the copolymerization of cyclohexene oxide（CHO）,carbon dioxide（CO₂）and L-lactide（LA）mixed monomers,the ZnGA-catalyzed selective copolymerization of mixed monomers was studied.First,the polymerization conditions were explored,including the effect of monomer molar feed ratio,reaction temperature,the amount of catalyst,solvent and CO₂ pressure on the copolymerization of mixed monomers.Then,the copolymerization reaction conditions were optimized to promote the implementation of selective copolymerization.The results of the study found that at 80°C,the copolymerization system was only CHO and CO₂ polymerized to produce polycarbonate（PCHC）during the first 6 hours of the mixed monomer reaction.After 6 hours,LA gradually participated in the reaction and the finally formed a gradient polymer with tapered structure.In order to synthesize the block polymer,the one-pot stepwise polymerization strategy was adopted.The structure of the obtained product was characterized by ¹H-NMR,¹³C-NMR,FTIR and DOSY NMR,which proved the successful preparation of the block copolymer,and the copolymerization mechanism was proposed.