Catalytic Polymerization Of O-lactate(OCA)Monomer To Synthesize Cyclic Polyester

O-lactone(OCA)is derived from a pentacyclic compound of amino acids.ROP of OCA involves entropy-driven decarboxylation and is thermally easier to open than lactide.And OCA rich side chain functional groups can increase the diversity of PAHA,improve its physical properties and mechanical properties,so it is of great significance to develop a catalytic system that can catalyze the controlled ring-opening polymerization of OCA monomers.At present,OCA ring-opening polymerization is mainly used to synthesize linear polyesters,and there is little research on its synthesis of cyclic polyesters.Cyclic polyester differs from linear polyester in density,viscosity,etc.and exhibits some excellent properties.Therefore,in this paper,OCA ring-opening polymerization to produce cyclic polyester was launched.1.This article uses 1,4-diazabicyclo[2.2.2]octane(DABCO),benzyl alcohol(BnOH)and triethylboron in tetrahydrofuran solution[TEB(THF)]to form a three-way catalytic system which can catalyze controlled ring-opening polymerization of PheOCA monomer at room temperature.After optimizing the polymerization conditions,the reaction conditions were determined as TEB:DABCO:BnOH=0.75:0.75:1,and the reaction solvent was toluene.When the monomer dosage is 50 eq,the molecular weight distribution of the obtained polymer is narrow(D=1.13),and the isotacticity is relatively high(Pm=0.83).MALDI-TOF MS proved that the obtained polymer was a cyclic polymer.Experiments prove that this polymerization reaction is living polymerization,the molecular weight of the polymer is as high as 46.9 KDa,and the molecular weight distribution is less than 1.25.The thermal stability of the obtained cyclic polymer is compared with the corresponding linear polymer.The thermal decomposition temperature of the cyclic polymer can reach 359?,which is nearly 30? higher than that of the corresponding linear polymer.2.To study the interaction of the catalytic system through the nuclear magnetic resonance hydrogen spectroscopy,carbon spectroscopy,nitrogen-hydrogen two-dimensional spectroscopy,at the same time,the polymerization kinetics was studied,and the possible polymerization mechanism was proposed.That is,the interaction between BnOH and DABCO to form hydrogen bonds weakens the nucleophilic nature of DABCO,the two tertiary amines N of DABCO attack the monomer nucleophilically and initiate ring-opening polymerization of the monomer.When the polymer chain is extended to a certain extent,the O-at the end of the chain can attack the N+of DABCO to bite back to form a cyclic polymer.3.The applicability of the cyclic polyester synthesis route was studied,and it was found that the combination of the organic base TMEDA which are similar in structure to DABCO and BnOH,TEB;the combination of the organic acid thiourea and DABCO,BnOH;The combination of amine,TEB and DABCO can catalyze the ROP of L-PheOCA to form cyclic polyester.