Study of the conformational rigidity of polyelectrolytes by elastic neutron scattering: 2. Molecular dimensions and conformation of poly(methacrylic acid)

Elastic neutron scattering at small angles allows the radius of gyration of a PMA sample of molecular weight M_v ～ 13000 to be measured in highly dilute solution; the variation of this parameter with concentration and charge density to be followed, and the viscometric results to be confirmed. The scattered intensity is proportional to q^?2(q = momentum transfer) for the highest concentrations studied, which correspond to a Gaussian distribution function of the sub units of the chain, and to q^?1 at the lowest concentrations, of which it is concluded that the polyion is then a zig-zag with only a few subunits.