Fiber formation from atactic polystyrene (aPS) and alternating poly(styrene-maleic anhydride) (PSMA) synthesized by free radical polymerization (AIBN, 90 degrees C, 4 h) were investigated by electrospinning from various Solutions. aPS was soluble in dimethylformamide (DMF), tetrahydrofuran (THF), toluene, styrene, and benzene, whereas PSMA was soluble in acetone, DMF, THF, dimethylsulfoxide (DMSO), ethyl acetate, and methanol. aPS fibers Could be electrospun from 15 to 20% DMF and 20% THF Solutions, but not from styrene nor toluene. PSMA, on the other hand, Could be efficiently electrospun into fibers from DMF and DMSO at 20 and 25%, respectively. Few, PSMA fibers were, however, produced from acetone, THF, or ethyl acetate Solutions. Results showed that solvent properties and polymer-solvent miscibility strongly influenced the fiber formation from electrospinning. The addition of solvents, Such as THF, generally improved the fiber Uniformity and reduced fiber sizes for both polymers. The nonsolvents, however, had opposing effects on the two polymers, i.e., significantly reducing PSMA fiber diameters to 200 to 300 nm, creating larger and irregularly Shaped aPS fibers. The ability to incorporate the styrene monomer and divinylbenzene crosslinker in aPS fibers as well as to hydrolyze PSMA fibers with diluted NaOH solutions demonstrated potential for post-electrospinning reactions and modification of these Ultrafine fibers for reactive Support materials. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 2709-2718, 2009