SYNOPSISPolystyrenes with different molecular weights were chemically modified with maleic anhydride by use of certain cationic catalysts of Lewis acid type (BF3.0Etz, AlC13, TIC4, ZnClz, FeC13, and SnCl,) in chloroform. The effects of molecular weight of polystyrene, as well as type of Lewis acid used, on properties and structure of products were investigated. The interrelation between the molecular weight of polystyrene and content of carboxyl groups in the products was made. A direct relationship between the activity of catalyst used and the number of carboxyl groups was found. For characterization of side-chain functionalized polystyrene, fractional precipitation was applied which yielded carboxyl groups in all fractions. The carboxyl group concentrations were found to be the highest in the case of BF3 -OEtz. Modified polystyrene samples containing -CO -CH = CH -COOH fragments in side chains are easily crosslinked at 14O-15O0C and by UV irradiation as proved by IR, DTA, and TGA analyses. INTRODUCTIONThe reaction of maleic anhydride with commercial polymers such as polyethylene, ' 9' polypropylene, ethylene-propylene c~p o l y m e r ,~ polystyrene, and styrene-( ethylene-butylene ) -styrene block copolymer6 in the presence of peroxide catalysts were investigated extensively. In most of these studies, the possibility of the addition of anhydride units on the polymer backbone accompanied mainly by crosslinking and degradation of macromolecules has also been demonstrated.On the other hand, modifications on the side was shown that new coating systems with improved heat resistance, anticorrosive, and impact properties can be obtained.I5-l7 Thus, functionalization of polystyrene can be carried out either via the polymer backbone in the case of radical catalysts or through the side chain of macromolecules (phenyl rings) using cationic catalysts. The present work was undertaken to study the side-chain modification of polystyrene with maleic anhydride in the presence of various Lewis acids. The main objective of the study was to reveal the effect of the molecular weight of polystyrene and the type of Lewis acid used as a cationic catalyst on the structure and properties of the resulting functionalized polystyrenes. EXPERIMENTAL MaterialsPolystyrene (PS) used was of emulsion ( M , = 5.0 -lo5) and/or of bulk type ( M , = 2.5. lo5). Maleic anhydride (MA) used was purified by recrystallization from benzene followed by sublimation in vacuum; mp 52.8"C. The Lewis acids such as BF3 * OEt,, AlC13, TiCl,, ZnCl,, FeC13, and SnC14 were commercial products and all were distilled under nitrogen atmosphere, diluted with chloroform, and sealed in glass ampules. ModificationFor modification of PS, 5.2 g (0,05 mol) of PS and 40 mL of chloroform were mixed and stirred in a flask at 2OoC for 2 h to which 0.98 g (0,Ol mol) of MA (corresponding to 20 mol % MA with respect to PS) was added and all were stirred for another hour. Above this solution, a t the same temperature, the catalyst ( BF3 -OEt,) was added dropwise and all were stirred ...

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Novel functionalized polystyrenes having groups such as epichlorohydrin, epoxy, acetyl, C=C double bond, and carboxyl were synthesized by the reaction of polystyrene with epichlorohydrin, unsaturated hydrocarbons, and organic anhydrides in the presence of Lewis acid catalysts. The adhesion capability and corrosion resistance of the new synthesized functionalized polystyrenes to metals under various conditions were investigated. A very good relationship was observed between the quantity of functional groups bonded to the aromatic rings of the polystyrenes and the adhesion and corrosion resistance properties of the polyfunctionalized polystyrenes. It was also observed that the new polyfunctionalized polystyrenes obtained by chemical modification with maleic anhydride, acetic anhydride, isoprene, butadiene, and epichlorohydrin in the presence of cationic catalysts resulted in high adhesion and anti-corrosion properties.

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