Regular Star-Shaped Fullerene(C60)-Containing Polystyrenes in Solutions: SANS Aspect

Abstract

Structure and conformations of regular star-shaped polystyrenes with single or doubled C60-centers and various lengths of arms have been studied in D-toluene by small-angle neutron scattering. For oligomers (∼4 or ∼10 units in an arm), stretching of the arms’ conformation was observed. This effect was also revealed in stars with longer arms (70–100 units) at a local level (inside a segment), and an enhanced swelling of stars as compared to the Daoud–Cotton theory was observed. Meanwhile, for massive stars (∼400 units in an arm) the individual properties of the arms in correlation spectra were not pronounced. The conformation of their arms did not deviate substantially from the one for free linear chains. A following study of stars with mono- and double (C60−C60)-centers and functionalities f = 6 and 12 has shown the increased stiffness and dimensions of arms in stars with functionality f = 6 and 12 as compared to linear precursor. However, for multi-arm stars (f = 22), the arms’ higher flexibility was observed. These effects are explained by a competition between the ordering of solvent near the fullerenes (columnar structures) and the action of grafted arms disturbing the packing of the solvent at the fullerene surface.