Following Hurion, Kundt in 1886 published two articles (Kundt 1886a; Kundt 1886b) that delved into the issues of optical anisotropy
, which were relatively new at the time.
5d, when the composite is crystallized under [CO.sub.2] at low pressure in which the number density of spherulite N is larger than that under air at ambient pressure, the spherulite is coarser than that obtained under air at ambient pressure: that is, the arrangement of the lamellar stacks are much disordered and the optical anisotropy
in the spherulite is weaker.
The interference pattern of the writing beams leads to a spatially modulated optical anisotropy
of the phase type [DELTA]n([chi]) (refractive index modulation) and/or the amplitude type [DELTA][alpha]([chi]) (absorption modulation) and also, in the case of azobenezene functionalized polymers, to the surface modulation [DELTA]d([chi]).
The stress-optical behavior can be understood from the thermo-viscoelastic properties of polymers governing the qualitative behavior and the molecular design, which determines the sensitivity of a polymer to stress-induced optical anisotropy
. The latter will be discussed in the next section, which gives arguments for the kind of molecular modifications that were made in the investigated polycarbonates.
They found that both PMDA/ODA and BPDA/PDA films possess significant optical anisotropy
that should result in dielectric anisotropy.