Influence of AlCl_3 on the optical properties of new synthesized 3-armed poly(methyl methacrylate) films


Abstract: Three-armed poly(methyl methacrylate)[PMMA] was synthesized by atom transfer radical polymerization at 100 °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, ^1H-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 AlCl_3 content. The wide band tails increased in width and the optical energy gap decreased from 2.39 to 1.28 eV as the AlCl_3 content increased from 0% to 15%. Analysis revealed that the type of transition is the indirect allowed one.

Keywords: Optical constants, optical band gap, dispersion parameters, thin films, ATRP, PMMA.

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