Large-amplitude motion in polymer crystals and mesophases
- Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemistry
Large-amplitude motion of macromolecules involves mainly rotation about bonds (conformational motion). In the liquid phases, the large- amplitude motion is coupled with disorder and accounts for the flow and viscoelastic behavior. Perfectly ordered crystals, in contrast, permit only little large-amplitude motion. The mesophases are intermediate in order and mobility. In crystals, large-amplitude motion leads initially to gauche defects and kinks (conformational defects), and ultimately may produce conformationally disordered crystals (conis crystals). Molecular dynamics simulations of crystals with up to 30,000 atoms have been carried out and show the mechanism of defect formation, permit the study of the distribution of defects, and the visualization of hexagonal crystals. Distinction between main-chain liquid-crystalline macromolecules and condis crystals, the two mesophases of polymers, can be done on basis of analysis of phase separation (partial crystallinity), present in condis crystals and not in liquid crystals. Solid state NMR is the tool of choice for detecting mobile and rigid phases. In highly drawn fibers one can find four different states of order and mobility. Besides the (defect) crystalline phase and the isotropic amorphous phase, an intermediate oriented phase and a rigid amorphous phase exists.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- National Science Foundation, Washington, DC (United States); USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 224748
- Report Number(s):
- CONF-940703-1; ON: DE96009627; CNN: Grant DMR 90-00520
- Resource Relation:
- Conference: 35. International Union of Pure and Applied Chemistry (IUPAC) symposium, Akron, OH (United States), 11-15 Jul 1994; Other Information: PBD: [1994]
- Country of Publication:
- United States
- Language:
- English
Similar Records
Mesophases in polyethylene, polypropylene, and poly(1-butene)
The detection of conformational disorder by thermal analysis