Comparative Raman study of photopolymerized and pressure-polymerized ${\mathrm{C}}_{60}$ films

We have made a Raman study of low-pressure polymerized and photopolymerized ${\mathrm{C}}_{60}$ films, polymerized in different ways, but otherwise initially identical. Although the structures developing in the films during polymerization are initially very similar, an analysis of characteristic features in the Raman spectra shows that photopolymerized material forms a more complex polymeric structure when the polymerization approaches saturation. We suggest that this complex structure contains branched polymeric chains and in particular that a mode near 1454 ${\mathrm{cm}}^{\mathrm{-}1}$ in photopolymerized ${\mathrm{C}}_{60}$ is characteristic for this type of structure.