TABLE OF CONTENTS The refractive index is the most important optical property of polymers. This characteristic is directly associated with the dielectric constant of the substance. In the general case, three molecular processes contribute to the statistic dielectric constant: orientation of constant momenta in a field, the relative displacement of positive and negative ions inside the molecule and the displacement of electrons in relation to nuclei. These three processes describe orientational, atomic and electron polarization, respectively.
In the area of sound frequencies, the dielectric constant is usually independent of frequency. As frequency increases, orientational polarization falls behind the field and finally has no effect on the dielectric constant. Usually, this transition proceeds in the area of radio frequencies. At much higher frequencies, usually in the infrared range, another type of transition is observed, when the frequency of influence approaches self frequencies of ion oscillations or exceeds them. In the optical range, the contribution of orientational polarization is negligible; the contribution of atomic polarization may also be neglected. In this range, not the dielectric constant ? but refractive index n is measured, the square of which equals ? under the condition that both these values are determined at one and the same frequency. The refractive index somewhat changes with frequency in the optical range which is associated with a gradual approximation to self frequencies of oscillation of electrons existing in the ultraviolet range.
The simplest method, in which an attempt is made to take into account electrostatic interactions...
