Journal of Physical Chemistry B, Vol.109, No.24, 11913-11917, 2005
Structure of the crystalline C-60 photopolymer and the isolation of its cycloadduct components
We produced C-60 photopolymer in gram quantity by a new monomer recycling method and extracted its soluble components. The most abundant components, the (2 + 2) cycloadduct dimer, C-120, and several oligomers were isolated by high-performance liquid chromatography (HPLC). Three different C-180 isomers were identified on the basis of their formation and decomposition reactions. The crystal structure of the insoluble photopolymer is face-centered cubic (fcc) with a contracted lattice parameter relative to the pristine C-60. The lattice parameter and the amounts of soluble oligomers depend on the preparation temperature. We explain this variation with a topochemical model of photopolymerization: The geometrical conditions allow the formation of only linear or planar oligomers in the triangular or square sublattices. Competing reactions in the intersecting planes prevent the formation of large oligomers. The lattice contraction is proportional to the number of cycloadduct bonds.