Small-angle X-ray scattering of polyethylene single-crystal suspensions

Small-angle X-ray scattering from oriented mats and random suspensions of polyethylene single crystals has been studied. A modification of the Guinier equation for platelets was derived to accommodate the two-phase nature of polymer lamellae. This modification also permitted the modelling of various degrees of interaction between lamellae and suspending media. Dried crystal mats show an increase in fold period on contact with potential solvents. Crystals which have never been dried show no evidence of penetration of the fold surface by the same liquids. Apparently the drying process causes a reorganization of the surface of the lamellae. Since the fold surfaces of crystals in suspension are unaffected by the liquids used, it is reasonable to assume a `tight' fold surface model. Crystallinities calculated with this model are in excellent agreement with recent differential scanning calorimetric data on crystals kept in suspension.