Fluorescence of copolymers of 2-naphthyl methacrylate and methyl methacrylate

The fluorescence of a series of copolymers of 2-naphthyl methacrylate (2-NM) and methyl methacrylate (MMA) with various contents of 2-NM (obtained in chloroform, carbon tetrachloride and acetonitrile) was investigated. A linear dependence between the ratio of the excimer to monomer emission intensities (I_D/I_M) and the diad fraction (f_nn) of 2-NM monomer units was established. The relationship between I_D/I_M and f_nn · I_n (I_n = the mean sequence length of 2-NM units) fits a logarithmic curve. The results indicate that the excimer emission is determined mainly by the nearest neighbour naphthalene-containing monomer units in the copolymer chain. The copolymers obtained in acetonitrile have higher values of I_D/I_M than those obtained in chloroform and carbon tetrachloride. This difference is due to the higher content of mm-triads in copolymers from acetonitrile, confirmed by ¹H-NMR analysis of the samples of poly(methyl methacrylate) formed from copolymers of 2-NM and MMA.