Two-dimensional small-angle analysis of isotactic polybutene stretched from the melt

Abstract

It is shown that unique information of the paracrystalline superstructure can only be obtained from high oriented polymers by applying a two-dimensional analysis of small-angle scattering with a high resolution pinhole camera. In this way the X-ray small-angle diffraction of isotactic polybutene stretched from the melt was investigated. It is quite similar to that of hot-stretched and annealed polyethylene along the meridian, but quite different orthogonally to it. The ultrafibrils have an average diameter D of 370 Å in the lateral direction orthogonal to the fiber axis and are built up by H = 100 Å long paracrystals in the fiber direction, alternating along this axis with 235 Å thick “amorphous” layers. Laterally the paracrystallites are aligned so that 70% are nematiclike with g₁₃ ∼ 32% and 30% smecticlike with g₁₃ ∼ 6%. In the rolled material a weak interference appears; at ∼250 Å on the equator, indicating that the ultrafibrils in the rolled material have a quite uniform diameter and grain boundaries with lower density in between them. If one does not take into account the scattering outside of the meridian and only discussed the meridional scattering, putting the radial paracrystalline lattice factor Z_r arbitrarily as unity, this one-dimensional analysis leads to wrong results with much too large H-values and too small values of g₃₃, g_3r, and g_r3, and no information about D, g_rr, and g_3r.