Three-armed poly(methyl methacrylate)[PMMA] was synthesized by atom transfer radical polymerization at 100 degrees C using benzene-1,3,5-triyl tris(4-(bromomethyl) benzoate as 3-armed initiator and a cuprous(I) bromide/2,2'-bipyridine catalytic system. The characterization of PMMA was confirmed by FT-IR, H-1-NMR, GPC, DSC, and TGA techniques. Optical absorption measurements were also studied by UV-VIS technique. Transmittance and reflectance measured in the wavelength range 300-700 nm were used to calculate the optical constants. The changes in dispersion and Urbach parameters were investigated as a function of AlCl3 content. The wide band tails increased in width and the optical energy gap decreased from 2.39 to 1.28 eV as the AlCl3 content increased from 0% to 15%. Analysis revealed that the type of transition is the indirect allowed one.