Casein proteins are soluble in 5% aq. ethanolamine, triethylamine, and triethanolamine, but insoluble in organic solvents. Graft copolymerization of casein (40 g/L) with acrylonitrile (AN) was carried out in 5% w/v aq. triethanolamine at 60 degrees C using potassium persulfate K2S2O8 as an initiator. Percent grafting and grafting efficiency increased with increasing initiator concentrations (up to 1.7 x 10(-2) mole L-1) and reaction times, but decreasing [M]/[I] ratios. Fourier transform IR spectra confirmed the formation of the acrylonitrile-grafted-casein (AN-g-casein) copolymers. Under the reaction conditions studied, the grafted PAN side chains were characterized by gel permeation chromatography to have M-n between 1.58 and 5.88 x 10(4) dalton and polydispersities between 2.6 and 4.5. The AN-g-casein copolymers behaved more like a PAN homopolymer in terms of their thermal properties and solubilities. The decomposition temperatures of AN-g-casein copolymers were between 255 and 273 degrees C, closer to the T-d of the PAN homopolymer (275 degrees C) and significantly higher than that of casein (180 degrees C). The AN-g-casein copolymers are soluble in 50% aq. NaSCN and ZnCl2, but are insoluble in 32:28:40 wt % CaCl2/CH3CH2OH/H2O like PAN and dimethylformamide-like casein.