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.

ABSTRACT:The cholesteric mesophase of poly(y-benzyl L-gultamate) in concentrated solutions of helicogenic solvents was investigated by the laser-light scattering technique. The observed, elastic scattering intensity distributions are theoretically explained in terms of the cholesteric domains embedded in an optically active medium. Analysis of the scattering patterns provides information on the identity period and sense of the cholesteric twisting.KEY WORDSThe laser-light scattering technique has been developed to characterize the supramolecular structure of polymeric systems in solution and in the liquid and solid states. In this series of papers, we study the application of this technique to the supramolecular structure of polypeptides in concentrated solutions and in solids.A number of reports have been published on the supramolecular structure of polymer liquid crystals. There are even a few papers dealing with the application of the scattering technique for analyzing the cholesteric pitch 1 • 2 or to qualitatively the orientation correlations (which exist in solutions and in solids) and variation in these with solvent, film preparing conditions3.4 and applied fields. 5 Our main purpose in this paper is to gain some insight into the elastic light scattering behavior of cholesteric liquid crystals so as to further expand applicability of this technique.We shall study, both theoretically and experimen-* Present address:

ABSTRACT:We investigated the twisted structure in the cholesteric liquid crystals in which the directors n (parallel to axes of a-helical molecules of polypeptides) are helicoidally twisted about the helical axis. We propose here that this twisting occurs, in general, nonlinearly or inhomogeneously with displacement along the helical axis for the poly(y-benzyl L-gultamate) systems studied in this work, in contrast to a picture of 'linear twisting' appearing in earlier literature on the cholesteric liquid crystals. The inhomogeneous twisting in the cholesterics is exhibited most spectacularly in the multiple-order scattering maxima of a laser-light. The deviation from the homogeneous twisting was studied as a function of cell thickness, solvent, polymer concentration, temperature, and aging; the results indicate that the inhomogeneous twisting of the directors is a general phenomenon in the lyotropic liquid crystal system studied in this work. We present a theory for elastic light scattering from the cholesteric mesophase having inhomogeneously twisted structure.KEY WORDS Cholesteric Liquid Crystal I Poly(y-benzyl L-glutamate) I Light Scattering I Cholesteric Twisted Structure I Inhomogeneous Twisting I Homogeneous Twisting I Director I Multiple-Order Diffraction I We explored elastic light scattering from the cholesteric mesophase of poly(y-benzyl L-glutamate) (PBLG) in helicogenic solvents. 1 -3 We found that at a small momentum transfer vector q(l ql =(4njJc) sin (8/2) where Jc is the wavelength of light in medium and e is the scattering angle), the scattering (designated as 'rod-like scattering') depends on the dimensions and shape of the cholesteric domain 2 • 3 in which the helical axes of the cholesteric, twisted structure (oriented normal to the director n) have correlated orientation (see Figure 9). At large q where 1/S (S being one-half the cholesteric pitch P, the distance over which the director makes a complete rotation) the scattering (designated as 'cholesteric scattering') reflects the internal structure of the cholesteric domain, i.e., a periodic vanat10n of the orientation correlation of the director nor the optical axis din the twisted structure. 3 The 'cholesteric scattering' reaches a maximum intensity at qm or em satisfying Bragg's equation,

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