The graft copolymerization of acrylic acid onto low-density polyethylene films by simultaneous gamma-ray irradiation was carried out. The effect of water and ethanol as grafting solvents on the distribution of grafted poly (acrylic acid) in the low-density polyethylene films was studied with optical microscopy observations of dyed and sliced samples and attenuated total reflection/Fourier infrared spectroscopy analysis. When no vigorous homopolymerization occurred, both polyethylene and poly(acrylic acid) existed in the grafted layer, and the thickness of the grafted layer and the poly(acrylic acid) concentration in the grafted layer increased with an increasing degree of grafting, regardless of the grafting conditions, the former increasing faster than the latter. In comparison with water as the solvent, in the absence of the inhibitor, homopolymerization could be suppressed to a certain degree in the ethanol solvent system, whereas in the presence of the inhibitor, obvious homopolymerization occurred at a lower monomer concentration, and both the degree of grafting and the thickness of the grafted layer were lower. Such differences could be explained by the chain transfer and the relatively low solubility of poly(acrylic acid) in ethanol. In addition, an experimental scheme using optical microscopy to observe the dyed and sliced polymers was optimized. (c) 2006 Wiley Periodicals, Inc.