Abstract
Electrical birefringence values have been measured in pulsed fields for cellulose nitrate solutions in cyclohexanone by a compensation method based on sinusoidal modulation of elliptical light polarization. The specific Kerr constants K have been determined for nitrocellulose (NC) samples with nitrogen contents of 11·0, 12·1, 13· and 13·4%. This was done by extrapolation of concentration dependences of K to zero concentration. For the fractionated samples with N contents of 12·1 and 13·4% it was found that the experimental plots of K vs. MW of fractions are described by the theory of Kerr's effect in solutions of vermicular chains. The magnitude and the angle slope of the dipole moments of units relative to contour lengths of the NC chains have been evaluated. Birefringence relaxation has been investigated for NC solutions when the electrical pulse has ended, and the orientational relaxation times τ have been determined. On comparing τ values (obtained by extrapolation to zero concentration) with the intrinsic viscosity and MW of the fractions it is deduced that the NC chains have now acquired kinetic flexibility.
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