A series of modified polyacrylonitriles have been obtained with several primary amines, such as ethanolamine, ethylenediamine, ethylamine, n‐butylamine, and n‐octylamine, without any catalysts in DMSO. This paper presents the syntheses of these new modified polymers and discusses the resultant structures and reaction mechanism by IR, NMR, and UV spectra. Composition was obtained by elemental analysis. Moreover, some physical properties of polymer were also investigated. It was found that all these primary amines could initiate coloration of polyacrylonitrile, which involves linking up of adjacent nitrile groups, and also reactions of the amines with the nitrile groups. However, the product of polyacrylonitrile with ethanolamine and with ethylenediamine were soluble in water when the mole ratio of amine group to nitrile group was 2. This interesting fact promoted a more detailed study of the modification of polyacrylonitrile with these amines. Crosslinking of the products of PAN with ethanolamine (or with ethylenediamine) was achieved by heat treatment. A mechanism for the formation of crosslinking was proposed.
SynopsisGraft copolymerization of maleic anhydride (MA) onto PVA was carried out both in the presence and absence of the initiator. In the former case, the resultant was a copolymer containing a carboxylic acid and a k e h l e f i n i c side chain. Therefore, the reaction product, viscosity, gel content, and mechanical properties differed from the resultant of the latter, which was obtained by esterification of PVA by MA. Both resultants showed polyelectrolytes characteristics. The dependence of the grafting percentage on the concentration of the initiator, the concentration of the monomer, the reaction temperature, and the reaction medium was studied. Grafted copolymers after heat treatment showed remarkable mechanical strength in the wet state when compared with original PVA.
SynopsisGraft terpolymers were prepared by graft polymerization of a mixture of acrylonitrile (AN) and maleic anhydride (MA) onto PVA in DMSO solution using KPS as an initiator. Structure and solubility of graft terpolymers varied with the concentrations of KPS and MA. Both lower and upper critical values of KPS concentration varied with MA concentration, and the resulting reaction could be divided into three regions-crosslinked, hydrophobic, and hydrophilic regions. Structures of graft terpolymers were considered to be composed of homopolymer side chain grafted onto PVA while gelation occurred from the surplus radicals in PVA backbone to carry on the coupling reaction. The mechanical properties and viscosities increased with the increase of the wt % of AN in graft terpolymers; however, to increase AN content in PVA by increasing KPS concentration would bring about the oxidation scission and do damage to mechanical properties. Thus it becomes obvious that KPS can only be used at a suitable amount. INTRODUCTIONPolymer membranes have a wide range of use in industries, such as in the separation, purification, and concentration of substances. Poly(viny1 alcohol) (PVA) is a well-known membrane material with good film-forming ability, toughness, hydro-affinity, and easy availability; therefore, investigation has been reported for its use in the field of medical materials.' However, because of its high solubility, it has to be turned into a completely insoluble stable material with good mechanical properties. The most common method is the graft copolymerization of hydrophobic monomers to PVA main chain by chemicals and irradiations2On the other hand, a polymer containing hydrophilic and hydrophobic microphase separation may improve its anti-clotting characteristic^.^ The purpose of this study is to use maleic anhydride (MA) as a hydrophilic monomer and acrylonitrile (AN) as a hydrophobic monomer through grafting so as to prepare terpolymers, in which both AN and MA were grafted onto PVA. The preparations and the properties of membranes were investigated. EXPERIMENTAL MaterialsPVA BF-17, a products of Chang Chun Petrochemical Co., Taiwan, DP = 1700, degree of saponification of 98. Graft TerpolymerizationAll grafting terpolymerizations were carried out in a four-necked flask equipped with a magnetic stirrer, thermometer, condenser, and nitrogen inlet. The general experimental procedure as example were as follows: PVA 5 g and MA 2 g were dissolved in 95 g DMSO, which was first stirred in a n atmosphere of nitrogen. Then AN 15 g was added and stirred until there was a homogeneous solution. Added afterward with 0.2 g of initiator KPS, the solution was then allowed to react at 60°C for 5 h. The reaction was stopped at the predetermined reaction time by adding a small amount of hydroquinone. The reaction mixture was concentrated to about 20% of its original volume at 60°C under reduced pressure and was then added to chloroform to precipitate the polymer. Purification of CopolymerThe products precipitated from chloroform we...
SYNOPSISA membrane was designed for the separation of a water-alcohol mixture by pervaporation on the basis of the difference in hydrogen-bonding interaction between two components of the membrane. Two kinds of poly (vinyl alcohol) -g-maleic anhydride/methyl methacrylate membrane were prepared by different methods: ( 1) A homogeneous membrane was formed by casting from dimethyl sulfoxide solution after purification. ( 2 ) A porous membrane was obtained directly by casting from the reaction solution, and then was purified. It is found that water was permeated through a homogeneous membrane preferentially in all ranges of feed compositions. Moreover, the flux was found to decrease with increasing PVA content in the membrane. The porous membrane after heat treatment has selective permeability for methanol. Pervaporation of water was investigated with respect to the feed concentration and also to the operating conditions. The effect of the molecular size of the permeating species on both permeation and separation is also discussed.
SUMMARYThe permeation and separation characteristics of alcohol/water systems through porous PVA membranes were investigated. Porous PVA membranes with different pore size and number were prepared by solution blending of PVA with several synthesized polymers or copolymers, such as polyacrylic acid, polyacrylamide, polyacrylonitrile, and methylmethacrylate-co-maleic anhydride, etc. Then casting, and finally extracting the blended polymers or copolymers by solvent from the membranes. The dependency of both permeation and separation on the molecular size and shape of the permeating species was dicussed qualitatively. Moreover, the permselectivity was investigated with attention to the feed composition of alcohol/water mixture and the effect of pore size and number. The selectivity was found to depend on the weight ratio and the molecular weight of polymer introduced to the membrane. When the weight ratio of polymer introduced into the membrane was larger than 0.1, methanol was permeated through membrane preferentially in methanoVwater system, and the separation factor increased with increasing the methanol feed concentration. On the other hand, membrane had a selective permeability for water in the other alcohol/water systems. The influence of operating conditions was also studied. ZUSAMMENFASSUNG:Es wurde das Permeations-und Trennverhalten von Alkohol/Wasser-Systemen durch porose PVA-Membranen untersucht. PVA-Membranen mit unterschiedlicher Anzahl und Grdrje von Poren wurden uber Mischungen in Liisung mit verschiedenen synthetisierten Polymeren und Copolymeren, wie Polyacrylsaure, Polyacrylnitril, Polyacrylamid, Poly(Methylmethacry1at-co-Maleinsaureanhydrid) etc., anschlierjendes
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