Studies of reactions with polymers. II. The reaction of maleic anhydride with acrylonitrile onto PVA and the properties of the resultant

Abstract

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...

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