Chain Conformation and Crystal Structure of Stereoregular Polydienes

Abstract

The conformations of a molecule represent different spatial arrangements of the atoms in a molecule, with a given con stitution and configuration, that may anse by rotations about single bonds. The assignment of the conformation to a ma cromolecule in the crystalline state, therefore, consists in the specification of the internal rotation angles that characterize its molecular structure. The conformation of macromolecules in the crystalline state is dependent on their configuration. The prin ciples underlying the conformation of macromolecules in the crystalline state can be summarized by the so-called equiva lence and minimum conformational energy principles; the equiv alence principle may be stated in this way. Starting from the consideration that in linear crystalline polymers the axis of the macromolecule runs parallel to a crystallographic axis of the crystal, the chain must be built up by structural units that occupy geometrically equivalent positions with regard to that axis; however, they are not bound to be crystallographically equivalent.