Pyridine-and 4-vinylpyridine-based Anion Exchange Membranes And Their Transport Properties

Ion exchange membrane is a type of ion exchange resin in the shape of membrane.They are used in many fields,such as desalination of seawater and saline water;however,there is still a great challenge in exploring high-permselectivity membranes so as to separate ions of a sigh and/or charge.The preparing methods of ion exchange membranes vary with the species of membranes.Among these methods,the preparation of homogeneous anion exchange membranes is one of the most difficult since chloromethyl ether,a extremely toxic chemical,is often employed for chloromethylization.So it is necessary to find a route of preparing anion exchange membrane without using chloromethyl ether.Meanwhile,there are growing demands for the ion exchange membranes with high thermal,chemical,and mechanical stability,low membrane resistance,and high permselectivity.When pyridine or its derivative(4-vinylpyridine)is used to aminate bromomethylated poly(2,6-dimethyl-1,4-phenylene oxide)(BPPO),a series of anion exchange membranes can be obtained.The prepared anion exchange membranes can effectively separate some monovalent anions with different hydration free energy.The dissertation comprises six chapters.Chapterâ… gives an overview on the research background-ion exchange membrane:classification,preparation, application,and development.Then the research ideas and outlines are purposed.In chapterâ…¡,a series of anion exchange membranes are successfully obtained by amination of pyridine on BPPO base membranes.Since pyridine is lower in hydrophilic-lipophilic balance(HLB)value than trimethylamine(TMA), the membranes prepared from pyridine will be higher in hydrophobicity than those prepared from TMA.The properties of the prepared anion exchange membranes are systematically investigated.In chapterâ…¢,a series of anion exchange membranes are successfully obtained by amination of 4-vinylpyridine on BPPO base membranes.The use of 4-vinylpyridine can introduce pyridinium groups into the base membrane and avoid the degradation of pyridine in the base membrane.The hydrophobicity of the obtained membrane is relatively high.The properties of the prepared anion exchange membranes are systematically studied.The thermal and chemical stability of the membranes prepared from pyridine and 4-vinylpyridine respectively are compared.In chapterâ…£,the permselectivities of monovalent anions in the membranes prepared from pyridine or 4-vinylpyridine are further studied by experiments. And the factors impacting on membrane permselectivity to anions are fully discussed:the hydrophobicity of anion exchange membranes,and the Stokes radii and hydration free energies of the anions.A simple evaluation of microstructure and transport parameters through membrane conductivity is presented in chapterâ…¤.The method is based on the relation between these properties.The method is exemplified through a series of commercial membranes and some lab-made membranes.It is also validated on the basis of the linearity of equations,the comparison between calculated and reported parameters,and the reasonability of the predicted structural parameters.Chapterâ…¥is a summary of the dissertation.Some important conclusions for preparation of the anion exchange membranes are underlined.