SHORT-RANGE ORDER EFFECTS IN AMORPHOUS POLYCONDENSATES AS STUDIED BY SPIN-POLARIZED DIFFUSE NEUTRON-SCATTERING AND SIMULATION

Short-range order effects in amorphous polycondensates, including the technologically important bisphenol-A-polycarbonate, have been investigated by elastic diffuse neutron scattering with spin polarization analysis. Selectively deuterated samples of each polycondensate have been used in order to vary the scattering contrast and thereby emphasize different pair correlations. The technique of spin polarization analysis allowed a reliable separation of the coherent scattering and an intensity calibration on the basis of the incoherent scattering as an internal standard. Thus, (d sigma/d Omega)(coh) has been measured directly by this method. The experimental results are compared to calculated cross-sections from computer-generated structures. Simulations have been performed with the ''amorphous cell'' method which models the static structure of the amorphous polymer in full chemical detail on the basis of a ''random coil'' conformation. The results of the simulations yield a fertile ground for the discussion of the measured cross-sections, though a direct comparison with the experiment is not always satisfactory. The observed discrepancies indicate a still insufficient structural relaxation of the simulated structures.