The influence of intermolecular interactions on the polymerization, 1·1H NMR investigation of solutions of naphthalene and methyl methacrylate,of 2-naphthyl methacrylate,and of 1-naphthyl methacrylate

The solutions of methyl methacrylate (MMA) and naphthalene (N), of 2-naphthyl methacrylate (2-NM) and of 1-naphthyl methacrylate (1-NM) in chloroform, acetone, acetonitrile and N,N-dimethylformamide are studied by ¹H NMR spectroscopy. In chloroform and in pure MMA, N causes a shift of the signal of the high field vinyl proton H_a of MMA to higher field, whereas in acetone and acetonitrile the signal of H_a has the τ-value for MMA in the absence of N. The H_a signals of 2-NM and 1-NM in acetone, acetonitrile and N,N-dimethylformamide shift downfield as compared with those in chloroform. The τ-value of the downfield vinyl proton H_b does not vary with a change of the solvent. The separation of the vinyl signals Δ=τ(H_a)—τ(H_b) becomes equal to that of pure MMA. The formation of 1:1 complexes between the electron donating naphthalene ring and the electron accepting methacrylic double bond is assumed. The stability constant of the MMA-N complex is 0,22 1.mol^?1. Some structures for the complexes are proposed on the basis of molecular models of the monomer molecules. The results confirm the known theories for the influence of the solvents in radical polymerization of MMA. They can explain the kinetic changes of polymerization of 2-NM and 1-NM.