Small-angle neutron scattering by semicrystalline polyethylene

The angular dependence of the intensity of neutron scattering by deuterated polyethylene chains (PED) dispersed in the protonated host (PEH) in the semicrystalline state has been computed over the scattering range 0 < μ < 0.2 Å−1, where μ = (4π/λ)sin(θ/2), for various morphologies that differ according to the mode of chain re-entry into the crystalline lamellae. The scattering functions vary strongly with the tendency for adjacent re-entry. The intensity in the range 0.04 < μ < 0.10 Å−1 is 30–40% greater for the regularly folded morphology than for the ‘switchboard’ model. Calculations for the latter approximate the experimental results of Schelten et al. Optimum agreement with their scattering intensities, and the chain dimensions and degree of crystallinity as well, is achieved by a statistical model in which the chain preferentially re-enters the crystalline layer with a probability of about 0.7. Re-entry, when it occurs, is not required to be adjacent to the preceding sequence.