Neutron scattering studies of the structure of amorphous and crystalline polymers and of polymer blends

The technique of neutron scattering for studying both the structure and dynamics of polymer systems is now well established. In the case of amorphous flexible polymers in most cases the bulk chain dimensions agree rather well with those of the unperturbed coil. Some newer results concerning for example side‐chain liquid‐crystal polymers and segmented polyurethane elastomers are described. Neutron small‐angle scattering can also be used for the investigation of the molecular deformation mechanism during the drawing process of polymers. In the case of semicrystalline polymers the way in which a single macromolecule traverses the crystalline and amorphous phases can also be evaluated by neutron scattering. A method has been proposed for the evaluation of the neutron scattering data without introducing detailed structural models. The only assumption made is that the molecular structure can be described as consisting of “clusters” of crystalline stems which belong to the same molecule. It is shown that this cluster model can be verified experimentally for the cases of poly(ethylene oxide), polypropylene and polyethylene. The structure factor S(q) in compatible polymer blends is usually treated by the random phase approximation according to de Gennes. The temperature dependence of S(q) displayed by some systems, however, appears to be anomalous within this approximation. A new method is presented for evaluating the neutron scattering data which takes into account that the Flory‐Huggins interaction parameter χ is not a point‐function χδ(τ), but can be interpreted in terms of a structure model χ(τ) which consists of spatially separated positive and negative contributions within a 1–10 å range. Finally the application of neutron scattering to diblock copolymers is discussed and it is shown that the results for the case of polystyrene‐poly (p‐methylstyrene) are in good agreement with the theoretically expected behaviour.