1990 Volume 6 Issue 1 Pages 27-32
The ultraviolet (UV) absorption spectra of styrene-alkyl methacrylate and -alkyl acrylate copolymers in chloroform solution altered with changing the styrene content. The molar absorption coefficients at 256.2 and 259.2nm were constant over the entire range of composition, while those at 262.8 and 269.6nm decreased with decreasing the styrene content. Hypochromic effects at the latter two wavelengths were observed. Wavelengths of 256.2nm and 259.2nm can be used as the key bands for the determination of the copolymer composition by UV. The bathochromic shift for the UV spectra of the styrene-alkyl methacrylate copolymers and the hypsochromic shift for those of the styrene-alkyl acrylate copolymers were observed. The hypochromic effect was independent of the types of comonomers; the ester group of the comonomer did not have any influence on UV absorption for the phenyl group. However, a methyl group attached to an α-carbon atom of the methacrylate monomer shifted the peak maxima toward lower absorption energies and a hydrogen atom on an α-carbon atom of the acrylate monomer toward higher absorption energies.
