| Anion exchange membrane in the field of modern industry has a wide range of applications,such as alkaline fuel cells,desalination and so on.However,how to easily and easily prepare the excellent anion exchange membrane is a bottleneck restricting the development of the membrane industry at this stage.The ion exchange capacity occupies an important position in the performance evaluation of the membrane,and the membrane with high ion exchange capacity,which is often prepared,has a high water content,which is very detrimental to the selectivity of the membrane.A large number of researchers have developed the addition of cross-linking agent to obtain good mechanical properties of the anionic film,but the fish and bear's paw can't have both,the addition of cross-linking agent will make the unit area within the functional group density decreased,thereby degrading performance.In the traditional membrane material production process,often use a large number of volatile organic solvents,but also through a series of complex processing procedures,the final preparation of the membrane performance is not very satisfactory.And the organic solvent used in this process is volatilized into the air due to the heat treatment process of the film-forming process,which not only causes great pollution to the air environment,but also makes a great deal of physical and mental health of the production staff of the membrane material The threat.In the experiment,a path of anion exchange membrane was prepared using the solventless method.After dissolving BPPO with VBC and styrene,two kinds of imidazole-like small molecules were quaternized to prepare the membrane.This process not only avoids the post-functionalization process but also makes the process without the use of organic solvents.All the substances in the system are carrying carbon-carbon double bonds which can cross-link reaction,so the liquid is heated at 100? to form a fully crosslinked structure.The full cross-linking structure is beneficial to improve the tightness of the membrane,and it is very good to adjust the water content caused by the high ion exchange capacity.A series of solvent-free films were prepared by adjusting the amount of p-chloromethylstyrene.The solvent-free scheme and the in-situ crosslinking method were designed to make the preparation process simple,and the performance was tested after the preparation was completed.Mainly the following:(1)In order to avoid the use of organic solvents,this paper uses p-chloromethyl styrene and styrene instead of solvent,the brominated polyphenylene ether dissolved,the quaternization,the system with a double bond structure,and finally heat.The mixture was treated to obtain a homogeneous anion exchange membrane structure.In order to take into account the ion exchange capacity and structural stability,the in situ crosslinking method is used to make the crosslinking site in the functional group position,which avoids the addition of the crosslinking agent and the exchange capacity(IEC)of the ionic membrane.Then,the basic performance of the solvent-free membrane was tested.It was found that the IEC of the solvent-free membrane also increased with the increase of the amount of VBC involved in the reaction,and the solvent-free membrane had high IEC(more than 2 mmol g-1),the results consistent with the expected,with the imidazole functional groups continue to introduce,will inevitably make IEC growth.However,while obtaining high IEC,the solvent-free membrane also has excellent ion migration(both around 0.94)and lower surface resistance(surface resistance less than 1.4?cm-2),which are high IEC advantage.As a result of the use of N-methyl imidazole in this experiment to adjust the degree of cross-linking solvent-free membrane to ensure that the film will not be too high degree of cross-linking and hydrophobic brittle,the overall cross-linking test to be more than 80%Its moisture content is also maintained between 40%-90%.The moisture content of the solvent-free series film increases as the IEC increases,and the moisture content of the film is controlled within a reasonable range due to the design of the fully crosslinked structure.(2)The electrochemical properties of the solventless series were investigated and discussed.The ionization ability of the membrane and the microstructural distribution of the conductive surface and the nonconductive region of the membrane were studied by means of chronopotentiometry.It was found that the concentration of solvent concentration of the solvent-free series film was later than that of the Japanese commercial anion film Neosepta AMX.With the reduction of VBC content,the migration start time is also constantly delayed,which shows that with the reduction of IEC,ion film transmission performance has been affected.The effective conductivity region coefficient(?)of the solvent-free membrane is above 0.986,which indicates that the micro-morphology of the solvent-free film is uniform.The limit current density of the solvent-1ree membrane is between 20.1-22.8 mA cm-2,which is much higher than that of the Japanese commercial film Neosepta AMX,by measuring the current density(i-v)curve of the ion film.14.2 mA cm-2,which makes the solvent-free film in the practical application may have better than Neosepta AMX electrodialysis performance.Therefore,the desalination rate of the solvent-free membrane was better than that of the Japanese commercial film,and the M-0.5 was the fastest,and the desalination was completed one hour ahead of Neosepta AMX.The speed of the membrane is significantly faster than the commercial film.Based on the above electrochemical test results,we can conclude that the anion exchange membrane prepared by solvent self-crosslinking method has excellent electrodialysis performance,especially M-0.5 has very high application value. |
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