Light scattering from polymer films having optically anisotropic rodlike texture. III. Inter‐rod interference

Abstract

SynopsisEffects of interparticle interference on depolarized light scattering from polymer films having nonspherulitic (rodlike, disklike, or fibrous) crystalline superstructures are explored, both theoretically and experimentally. Discrepancies between the observed "rodlike scattering" and the predicted scattering based on "single-rod" theory are pointed out and accounted for in terms of various types of aggregation models for polymeric solids and solutions. or fibril. These materials usually do not easily crystallize in spherulitic morphology.Rodlike scattering is observed both for crystalline solids and liquid crystals. This kind of scattering can be also found in materials crystallized from oriented polymer systems, as in tubular-extruded polyolefin film^,^^,^^ in material crystallized from stirred solutions,2s and in rubbers crystallized by ~t r e t c h i n g .~~ Rodlike scattering has been observed in many polymeric systems under various conditions.

Miscible blends of syndiotactic polystyrene and atactic polystyrene. Part 2. Depolarized light scattering studies and crystal growth rates

“…Thus, the DPLS patterns obtained from melt-crystallized samples are more likely to be representative of both spherulitic and rod-like morphologies. DPLS from the rod-like axilites will give a monotonic decay of intensity profile [24]. Our previous work demonstrated that spherulitic features are predominant at low T c ; whereas axilitic morphology is preferred at high T c : However, the fraction of axilites is more than 0.4 regardless of T c investigated.…”

Light Scattering by Shear-Induced Defects of Nematic Liquid Crystalline Polymers

“…The influence of diffraction effects on a light scattering pattern have been considered before for thin polymer films containing two-dimensional assemblies of anisotropic rods. 37 In our case, a 2D distribution is not enough because of the large thickness of the material in the transparent rheometer (about 400 µm) compared to the size of the individual defects. Loops are located at different levels and can contribute to the diffraction pattern due to the path difference between light beams scattered from different depths.…”

Polarized Light Scattering from Polymer Textures

“…Again, a four-lobe shape is observed as in the case of randomly (b) is again related to the orientation of the optic axes in the rodlike aggregate [27], As expected, the &dependence of the scattered light intensity is related reciprocally to the size of the rodlike unit [29]. There are features, however, which the simple single rod theory still fails to describe It is also of interest to introduce the coherent light scattering from assemblies of anisotropic rods [29-321. In the case of long range correlation in the orientation of rods and their optic axes, the effects of the associated interparticle interference lead to complex patterns.…”

“…In Figure 6 [29,31], various arrangements in a one-dimensional assembly of anisotropic rods are presented showing both the effect of the orientation of the rod axes and that of the optic axes upon the calculated H,-patterns. The problem of the interparticle interference was theoretically approached in terms of a modified Zernike-Prins theory or a paracrystal theory [29]. In general, the numerical calculations indicate that interparticle interference effects are significant at small scattering angles while the scattering from the assembly at large scattering angles can be described in terms of the single rod theory.…”

“…Effect of the orientation of rods (as determined by the angle () and effect of the orientation of their optic axes (as determined by the angle W O ) on the H,-scattering patterns of ordered rods' assemblies[29]. Schemes of their appropriate optical models where the lines indicate optic axes are inserted.…”