NEUTRON SCATTERING OF ANNEALED SOLUTION GROWN CRYSTALS: MOLECULAR DIMENSIONS.

Neutron scattering is used to investigate the dimensions of individual molecules and changes in relative positions of different molecules during the annealing of solution grown crystals of polyethylene. For annealing at 123 degree C or lower, the dimensions along the normals to the crystal lamellae increase approximately in line with the lamellar thickness. No significant effects of annealing time were found, within the experimental uncertainties. The dimensions in the plane of the crystallites remain approximately constant. For annealing at 125 degree C and 128 degree C the molecules become generally mobile since inter-molecular scattering effects occur, which implies a type of movement of molecules associated with fractionation. It is deduced that between 123 degree C and 125 degree C there is a demarcation between sizes of mobile regions: above, the regions are larger than molecules; below, they are smaller.