Recyclable Polymer Based On Six-membered Ring Lactone

Recyclable polymer is a material that is degraded into polymer precursors by catalytic degradation or pyrolysis.Adding recyclable properties to biodegradable polyester materials can effectively solve the environmental pollution caused by polymer materials and maximize the value of waste polymers.Therefore,fully recyclable polyester materials have received extensive attention.Poly(?-butyrolactone)is the first fully recyclable polyester material to be developed.With?-butyrolactone as the core,people have obtained several completely recyclable polyester materials with new structures through structural modification.However,monomers based on the five-membered ring core of?-butyrolactone are more difficult to modify in structure,and the polymerization conditions are relatively harsh,and it is difficult to form high molecular weight polymers.Therefore,expanding the monomer structure and developing new fully recyclable polyester materials are frontier topics in this field.In this thesis,six-membered ring lactones are used as the core,a new type of fully recyclable polymer material is constructed through monomer structure modification,and the polymer performance is tested.The specific research content is as follows:(1)The ring tension of the six-membered ring lactone monomer is significantly greater than that of the five-membered ring lactone monomer,which has the characteristics of easy polymerization,but the formed polymer has poor selectivity for depolymerization back to monomer.To this end,we introduced a spiro ring on the six-membered ring lactone monomer to reduce the ring tension design to achieve the six-membered ring lactone to construct a fully recyclable polymer.From?-methylene-?-valerolactone and isoprene,1,3-butadiene,cyclopentadiene and 2,3-dimethyl-1,3-butadiene,through Diels-Alder reaction constructs four new six-membered ring lactone monomers with spiro structure and unsaturated double bonds,namely M1,M2,M3,and M4,and further uses M1 and M3 palladium-carbon hydrogenation reduction reaction to prepare two new six-membered ring lactone monomers M5 and M6 with a spiro-ring structure.(2)Ln[N(Si Me₃)₂]₃(Ln=La,Y,Sm)/Bn OH,Zn[N(Si Me₃)₂]₂/Bn OH,Mg[N(Si Me₃)₂]₂/Bn OH,[Ln(OBn)₃]_x(Ln=La,Y)and[Zn(OBn)₂]_x catalyst systems and reaction conditions on the ring-opening polymerization of new spirocyclic monomers.[Ln(OBn)₃]_x was used as the optimal catalyst to prepare a high molecular weight linear polymer with a molecular weight of 338.2 kg/mol.The measurement of thermodynamic properties shows that the enthalpy of all polymerization reactions is around-19 k J/mol,which is significantly lower than the enthalpy of?-valerolactone polymerization.These results indicate that the introduction of the spiro ring effectively reduces the ring tension of the six-membered ring lactone.(3)PM1,PM2,PM5,and PM6 are fully recyclable polymers,which can be completely decomposed into polymer precursors under heating conditions,and the melting points of the polymers are between 98 and 134°C.Among them,PM5 is a typical thermoplastic with a fast crystallization rate.