Wide Angle X-ray Scattering Studies of C$_{60}$ Miscibility with Polymers

C$_{60 }$and other fullerenes have been shown to have limited solubility in common organic solvents and to form charge-transfer complexes with a variety of small molecules. Among factors that promote solubility and charge-transfer complex formation are aromaticity, electron donating capability, atoms much larger than carbon such as chlorine. However, studies of C$_{60}$ miscibility with polymers have been limited. We previously showed that C$_{60}$ has a miscibility limit of $\sim $1wt{\%} with polystyrene via wide angle x-ray scattering (WAXS) and molecular dynamics simulations. We have studied a series of polymers with structural features shown to be important in small molecule/C$_{60}$ interactions using WAXS: poly(para-phenylene ethynylene), poly(4-vinylpyridine), poly(vinylpyrrolidone), poly(4-chlorostyrene), poly(9-vinylphenanthrene), and poly(2-vinylnaphthalene). In each case, the point of C$_{60}$ aggregation, observable by WAXS, was taken as the miscibility limit for a given polymer system. The miscibility of C$_{60}$ in these polymers was correlated with the factors mentioned above and compared with the miscibility in solvents with analogous structures as the repeat units.