SOLUTION STRUCTURE OF COAL MACROMOLECULES IN PYRIDINE - SMALL-ANGLE NEUTRON-SCATTERING ANALYSIS OF UNTREATED AND O-METHYLATED COAL EXTRACTS

Small-angle neutron scattering (SANS) has been applied to investigate the solution state characteristics of pyridine extracts obtained from three Argonne Premium coals: APCS No. 3, 2, and 8. In order to investi gate the role of specific solvent-solute interactions, both untreated and O-methylated extracts were investigated. SANS analysis reveals tha t the solution structure of lower rank coal extracts exist as small pa rticles, with radii similar to 80 Angstrom, which loosely aggregate in to topologically complex solution structures. Details on the structure of the aggregates are obtained from the scattering behavior at low an d by assuming a pair correlation function which follows a power law de cay from the center to the perimeter of the aggregate. The dimensional ity of the aggregates indicates mass fractal topology. Changes in the solution state due to O-methylation are manifested in densification of the extended solution structure. The size and shape of the elemental particles appear unaffected by the derivatization chemistry.