Two samples of poly(ether sulfone)/poly (ether ether sulfone) alternative copolymer, showing marked differences in tensile behavior due to different thermal histories, were investigated by radial distribution function (RDF) methods. The RDF patterns were virtually identical and showed that the short range order (0-14 angstrom) in the samples had been essentially unaffected by the annealing procedures. Two intramolecular distances in the polymer repeat unit were successfully resolved in the RDF pattern. However, there were only suggestions of broad peaks at r = 5.5 angstrom and r = 11 angstrom attributable to intermolecular ordering, indicating that little intermolecular ordering had occurred in either sample. The appearance of two peaks at similar to 5 angstrom periodic suggested the existence of more or less parallel chain segments in the copolymers. Explanations of the different tensile properties of the two samples which assume a significant short range reordering on annealing are thus ruled out on the available evidence. A more highly annealed sample was examined to assess the sensitivity of the RDF method to short range intermolecular ordering. The RDF plot of this sample showed a marked periodicity peaking at intervals of similar to 5 angstrom which was attributed to intermolecular ordering, thus confirming the above conclusion. (c) 2007 Wiley Periodicals, Inc.