Nanophase-separated structures of flexible linear amorphous polymers on solids (I)- Grazing incidence wide-angle X-ray scattering study

Linear homopolymers have the simplest and most common macromolecular structures. The processes and end-use properties of these polymers largely depend on the spatial conformation and intermolecular packing. There is increasing evidence of a significant correlation between backbone to backbone, and side groups to side groups with a typical nanodomain size of about 1 nm even in amorphous polymer melts or semicrystalline polymer melts above their melting temperature. Here, we present a unique nanophase short-range periodic structure of side group and backbone correlation of amorphous chains adsorbed on solid substrates. Four linear homopolymers with different side groups, namely linear low-density polyethylene (no side groups), isotactic polypropylene (methyl side groups), atactic polystyrene (phenyl side groups), and poly(2-vinylpyridine) (pyridine side groups), are used as rational models. Strongly physisorbed polymer chains with a thickness of about 2 nm are prepared on silicon substrates using the established solvent rinsing protocol. In situ grazing incidence wide-angle X-ray scattering results show how the backbones and side groups of the amorphous polymer chains self-organize cooperatively in parallel and perpendicular directions to the substrate surface in a very local area. The effect of side groups on the self-organization process will be discussed.