STRUCTURAL INVESTIGATION OF STAR POLYMERS IN SOLUTION BY SMALL-ANGLE NEUTRON-SCATTERING

Using small angle neutron scattering, we investigated the conformation of star polymers with functionalities ranging from f = 8 to f = 128 i n a good solvent. The stars were made by anionic polymerization of iso prene or butadiene using multifunctional chlorosilane linking agents. Single star form factors at zero concentration were determined by extr apolating low concentration data to phi = 0. Conformations at finite c oncentrations were obtained by the zero average contrast method. In ge neral the star form factors are well described in terms of the Daoud-C otton scaling model. This concerns the molecular weight, functionality , and concentration dependence of R(G) as well as the shape of the for m factor. In particular the step height between the low Q and asymptot ic power law regime was found to follow an f3/2 law. Furthermore, with increasing functionality the star form factors were found to tend tow ard spherelike behavior, bearing evidence for a secondary maximum at t he position of the third oscillation of the corresponding sphere form factor.