Binary Lyotropic Systems. Comparison of Theory with Experiment

3 Binary Lyotropic Systems. Comparison of Theory with Experiment 

Experiments on liquid crystallinity exhibited by solutions of a-helical polypeptides have been especially illuminating (see Chapter 2 by Uematsu and Uematsu). Principal results are summarized and compared with theory in Table 2. Most of the measurements presented were carried out by visual observation between crossed 

4 Axial ratios may be calculated from chain diameters given by 

It should be noted that the tendency to form a nematic phase may be markedly diminished by departures from perfect helicity of the polypeptide chain. Experiments must therefore be conducted under conditions far removed from the helix-coil transition. Also, steric purity of the monomer units must be assured. Through their effect in disrupting perpetuation of the helix, as little as one percent of D-peptide units in an L-chain (or vice versa) may be expected to increase Vp considerably if the degree of polymerization is large, e.g., for a degree of polymerization DP 1000, or X 100. 

The biphasic gap appears to be little affected by the polydispersities of these polymers, contrary to predictions of theory cf. seq. 

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