The Construction Of Indoleamine Polymer Films Based On Cation-π And Performance Studies

Polymer film materials are widely used in environmental governance,energy,microelectronic devices and other fields.With the development of society and the progress of science and technology,the contradiction that the strength and toughness of polymer materials cannot be greatly improved at the same time has seriously hindered the application of polymer film materials.The traditional polymer strengthening and toughening methods mainly include nanomaterial modification and dynamic covalent crosslinking.Although these two methods have certain strengthening and toughening effects,they also show obvious disadvantages.For example,nanomaterial preparation is difficult and the dispersion is poor.Dynamic covalent crosslinking is based on covalent bonds as sacrificial bonds,which will damage the life of the product to a certain extent.Therefore,it is urgent to develop a method that can greatly improve the strength and toughness of polymer films at the same time.The cation-πinteraction is a special non-covalent interaction,which is the superposition of electrostatic interaction and van der Waals force between the positive ion center and the adjacentπelectron cloud.Because of its’point-surface’interaction,the binding area is large,which can improve the strength of the polymer;at the same time,this’point-surface’non-covalent interaction can be more easily formed and removed in the polymer network under external stimulation,which can better dissipate energy and improve the toughness of the polymer.Based on the above analysis,this paper hopes to greatly improve the strength and toughness of polymer films by introducing cation-πinteraction into the polymer network.The research content is divided into the following two aspects:(1)Indole-containing diamino compounds were prepared from 5-nitroindole and 4,4’-difluorobenzophenone.Linear polymers were prepared by polycondensation of diamino compounds and aromatic dianhydrides at low temperature;and Na~+was introduced into the polymer structure to prepare cationic-π-crosslinked polymer films(PI-Na).The successful introduction of cation-πinteraction into the molecular structure of polyimide was proved by spectroscopic characterization and simulation calculation.The tensile test showed that when Na~+:indole was 1:2,the mechanical properties of PI-Na film were the best.The tensile strength was 116 MPa and the elongation at break was 10.7%.Compared with PI film,the strength and toughness were increased by 84.4%and 167.5%,respectively.The thermal decomposition temperature of the film was increased from 434°C to 485°C,the thermal decomposition temperature was increased by 51°C,and the glass transition temperature was increased from 216°C to 244°C.The experimental results show that the introduction of cation-πinteraction can greatly improve the strength and toughness of polyimide film materials,and also improve their heat resistance.(2)The triamino monomer containing indole was prepared,and then reacted with epoxy monomer and sodium tert-butoxide to prepare epoxy polymer(PIN(X)).For the first time,the microphase separation of rigid and flexible chains of epoxy polymers was achieved by using cation-πinteraction as a driving force.The tensile test showed that the PIN-Na film had the best mechanical properties when Na~+:indole=1:20,the elongation at break was 128%,and the tensile strength was 8.5 MPa.Compared with PIN film,the tensile strength of PIN-Na film increased by 313%and the elongation at break increased by 217%.The internal mechanism of the improvement of mechanical properties of PIN-Na films is as follows:when stress is applied,the soft phase region can absorb energy through the deformation of molecular chains and networks,and the deformation is reversible below the critical value of stress.At the same time,the cation-πinteraction between indole and Na~+will also dissociate to further dissipate energy.The successful implementation of the microphase separation strategy was proved by AFM,DMA and other means.In addition,the thermal stability of PIN-Na film is also improved,and it has antibacterial effect.