Synthesis Of Polyether Ester By Step Polycondensation Of Titanic-sulfonic Acid Catalyst System And Its Properties

Poly（ether ester）copolymer（PEE）,with polyether soft segment and crystalline polyester as hard segment,is a kind of important industrial thermoplastic polymer,which has a wide applications in molded soles,ski boots,auto parts,wires and cables,shock absorbers and biomedical fields.At present,poly（ether-ester）copolymers are synthesized by polycondensation of hydroxyl-terminated polyether and polyester monomers at high temperature.Multi-block poly（ether-ester）（PBT-PTMO）with poly（butylene terephthalate）（PBT）as the rigid segment and poly（tetrahydrofuran）（PTMO）as the polyether flexible segment（PBT-PTMO）is the most extensive and in-depth research.Polytrimethylene terephthalate（PTT）has recently attracted great interest because of its excellent resilience and moderate modulus.The performance of polyether esters is related to different chain structure,however,adding poly（1,3-propylene glycol）to polyether esters remains a challenge.Therefore,we proposed a method of synthesis of polyether ester by melting polycondensation reaction with diacid and dialcohol as monomers.Firstly,a titanic-sulfonic acid compound catalytic system was designed to directly catalyze terephthalic acid（TPA）and 1,3-propylene glycol（PDO）.PTT-co-PDPT-co-PTr MOT with poly（trimethylene terephthalate）（PTT）as the crystalline hard segment,dipropylene glycol and oligo（1,3-propanediol）as the soft segment was obtained by melting polycondensation reaction,and the soft segment content was 66 wt%～45wt%,the intrinsic viscosity was between 0.60～1.06 d L/g.The mechanism of titanium-sulfonic acid composite catalytic system was analyzed in detail.Under the catalytic action of sulfonic acid,etherification reaction and esterification reaction of PDO were carried out simultaneously to obtain polyether ester oligomer,and high molecular weight polymer was obtained through polycondensation reaction.In addition,hydrogen bonds can be formed between sulfonic acid and TPT,which can inhibit the hydrolysis of TPT in the esterification stage and improve the efficiency of polycondensation stage.The initial thermal decomposition temperature of PTT-co-PDPT-co-PTr MOT was about 374°C,which was not affected by fragment content.When the content of ether segment increased from 45%to 66%,the melting temperature decreased from 165.2°C to 133.6°C,and the glass transition temperature decreased from 14.3°C to 5.8°C,mainly due to the addition of ether bond,which inhibited the crystallization of PTT.At present,the melting polycondensation reaction of diacid,diol and polyethylene oxide is the most commonly used method to obtain block PET polyether ester.Because the activity of hydroxyl terminal of polyether is affected by the chain length,the polymerization efficiency is reduced,and the length of each block and the molecular weight of polyether have a significant impact on the properties of polyether ester behavior.According to our new method for synthesizing poly（ether ester）,using TPT/MSA as catalyst to catalyze terephthalic acid（TPA）and ethylene glycol（EG）,we obtained random poly（ether ester）copolymer,which polyethylene terephthalate（PET）as hard segment,poly（diethylene terephthalate）（PDET）and poly（ethylene oxide terephthalate）（PEOT）were soft segments,and the ether segment content was between 55%and 86%.Adding multifunctional monomers,such as 1,1,1-trihydroxymethyl ethane（TME）,branched PET polyether ester copolymers were obtained.The condensation time was shortened to 1.5 h,and the intrinsic viscosity was increased from 0.49 to 1.04 d L/g.The initial thermal decomposition temperature of PET-co-PDET-co-PEOT was about 400°C,which was not affected by the structure and fragment composition.The introduction of ether bonds inhibited the crystallization and rigidity of PET,and the glass transition temperature was reduced to 25°C.The molecular weight and branched structure have significant effects on the mechanical behavior.When the content of ether segment was about 72%,the elongation at break of linear and branched polyether esters was 279.6 and 472.7%,respectively,and both PET-based polyether esters had good elastic recovery performance.Polylactic acid（PLA）has become the most promising polyester due to its renewability,biodegradability and good mechanical properties,but its brittleness has limited its application.An effective solution is to copolymerize with elastomers,so PET-co-PDET-co-PEOT elastomers are copolymerized with PLA.The first synthesis method used TPA,EG and LA three monomers as raw materials,and obtained the PEELA random copolymer with lactic acid content of 4 to 77%by melt polycondensation,and Y_LL was about 1.0.In the second synthesis method,PET-co-PDET-co-PEOT and poly（lactic acid）were used as raw materials,and PET-co-PDET-co-PEOT copolymers with LA content of 87～34%were obtained by heating up gradually during the copolymerization stage,and Y_LL could reach up to 36.3.Thermogravimetric analysis showed that the initial decomposition temperature of PEELA copolymer was 376.97°C,much higher than that of PLA.However,the PET-PEOT-PLA copolymer has two decomposition stages due to the long chain lengths of PLA and PET-co-PDET-co-PEOT.When the PLA content increases from 34%to 87%,the initial decomposition temperature decreases from 309.36°C to 296.50°C.When PLA content decreased from 87%to 74%,PET-PEOT-PLA changed from crystalline polymer（T_m=142.4°C）to amorphous polymer.When LA content was 35%,the tensile strength of PEELA and PET-PEOT-PLA was2.14 and 8.22 MPa,respectively,and the elongation at break was about520%.These results indicated that the thermal and mechanical properties of copolymer were affected by the length and content of PLA segment.Due to the presence of PLA,copolymers could degrade up to 50%within 28days in the presence of lipase,showing good biodegradability.