Polymers show cooperative phenomena for almost all of their properties, and this is no less true for the optical activity of chiral polymers. This phenomena was first observed by the 'Italian School' in their early work following the discovery of stereoregular polymerization, and let to observations of nonlinear relationships between enantiomeric characteristics of monomeric materials used in polymerizations and the polymers produced. These observations confirmed the hypothesis that the conformations of these polymers in the melt and dissolved states resembled those found in the solid crystal. In recent years a version of the Nylons, which failed to make the grade as a fiber, turned out to carry these cooperative properties of chirality to an extreme. Minute chiral forces control the chain properties, allowing experiments in which chirality arising from isotopic substitution, or solvation effects, or even nearly racemic states can be studied. Statistical physics and the one-dimensional Ising model describe the properties of these polymers in quantitative perfection and yield insight into how to manipulate the chirality and the polymer properties to gain even higher amplification of the chiral forces. Through work on such disparate materials as vinyl polymers and polyisocyanates, we discover the structural boundaries for these observations and therefore which other polymeric and supramolecular systems may behave similarly. This is already being seen. However, these studies also demonstrate that structural theory appears inadequate to interpret the small energies driving these chiral effects, and this has parallels in other areas where equilibrium states are balanced on cooperatively driven forces.
|Original language||English (US)|
|Number of pages||17|
|Journal||Angewandte Chemie - International Edition|
|State||Published - Nov 2 1999|
- Asymmetric amplification
- Helical structures
ASJC Scopus subject areas