| Abstract
| - The kind and degree of crystalline phase orientation for clathrate s-PS films, obtained bysolution-casting procedures, and for semicrystalline films, obtained by suitable treatments on these castfilms, are analyzed. Clathrate as well as nanoporous form films can present high degrees of uniplanarorientation, corresponding to the tendency of the ac crystallographic planes, to be parallel to the filmplane. The driving force for this kind of orientation is the tendency of rows of parallel s(2/1)2 helices withminimum interchain and maximum interplanar distances to be parallel to the film plane. A high degreeof uniplanar orientation is also maintained after annealing procedures leading to γ form, that is theother crystalline form which presents the same helical conformation. A tentative indexing of the γ formreflections, based on an orthorhombic unit cell, again indicates the presence of parallelism of ac planeswith respect to the film surface. A substantial planar orientation, corresponding to the placement of thechain axes parallel to the film plane can also be maintained after annealing procedures at highertemperatures (220−230 °C) leading to α and β crystalline forms, where trans-planar rather than helicalchains are included.
|
