Chapter 7 Structure and dynamics of crystalline and noncrystalline phases in polymers

Abstract

This chapter discusses the structural parameters and the dynamics of polymers obtainable from solid-state nuclear magnetic resonance (NMR). Most differences between crystalline and amorphous phases are attributed to the order and disorder of polymer chains. All polymer chains in a crystalline phase see neighboring chains at the same distance with the same mutual orientation. In contrast, neighboring chains in the amorphous phase exist at random distances and random mutual orientations. Therefore, there is room for molecular motion in the amorphous phase. As a result, the difference between the crystalline and amorphous phases appears in the relaxation times and chemical shifts. On the basis that the chemical shifts are affected by conformation through the electronic structure around the nuclei of interest, the chemical shift difference between the crystalline and amorphous phases is explained by the γ- gauche effect. In the crystalline phase, the methylene group takes a rigid trans-zigzag conformation, while the trans - gauche transition takes place rapidly in the amorphous phase.