Study On Self-healing And Reshaping Of Zwitterionic Shape Memory Polymers

Shape memory polymer is a novel stimulus-responsive smart polymer with unique shape memory properties.However,most current studies of shape memory polymers do not have self-healing properties,which greatly limits practical applications.According to previous research,Polymers can self-healing under the weak electrostatic force network structure of zwitterionic structures.Therefore,this thesis synthesizes zwitterionic polymers with shape memory properties,combining of shape memory properties and self-healing properties,and further explored the ability of reshape under hydration.First,we propose a new strategy to prepare humidity-responsive self-healing zwitterionic polyurethanes(M-ZPUs)based on a pyridine-type sulfobetaine prepared with N,N-bis(2-hydroxylethyl)isonicotinamide(BINA)and methylene diphenyl diisocyanate(MDI),following by ionization with 1,3-propanesultone(PS).The test of DSC and TGA showed that the sulfobetaine structure had some damage to the thermal properties of the series of samples.M-ZPUs have good mechanical properties and shape memory properties.The stress-strain recovery ofM-ZPU08 were 78.1% and 62.5% respectively,without the ability of completely repaired.Then,in order to improve the self-healing properties of the materials,a novel zwitterionic polyurethanes(H-ZPUs)were synthesized by BINA andhexamethylene diisocyanate(HDI),instead of MDI,following by ionization with 1,3-propanesultone(PS).The DSC and TGA tests showed strong electrostatic effect of the sulfobetaine structure,greatly affected the movement of polyurethane segments.H-ZPUs have good shape memory performance.The H-ZPU08 sample can be completely repaired at 60% RH and the shape memory properties can be well repaired.The self-healing properties of the sample are greatly improved with increasing humidity.Under the humidity condition,the water molecule is hydrated with the zwitterionic structure,and the soft segment phase structure can be rearranged.The self-healing properties of the sample are greatly improved with increasing humidity.Under the humidity condition,the water molecule is hydrated with the zwitterionic structure,and the soft segment phase structure can be rearranged.This is the process of rehsaping,which lead to eliminate the previous shape memory process and start the new shape memory.Finally,increases self-healing and shape memory properties by enhancing micro-phase separation.The novel zwitterionic polyurethanes(MH-ZPUs)were synthesized by the reaction of MDI and HDI,at a molar ratio of 4: 6,with BINA and following 1,3-PS.Compared with H-ZPUs,MH-ZPUs have better thermal stability and mechanical properties,and have better double recovery rate and triple shape memory performance in shape memory performance.At 60% RH,the MH-ZPU06 is completely repaired and the shape memory properties can be well repaired.Moisture is also a good factor for the self-healing of the MH-ZPUs.Under the interaction of water molecules with ionic structures,MH-ZPUs can be endowed with reshaping properties.