tion of the equilibrium stress-optical coefficients in connection with the light-scattering results shows that the reorganized regions should exhibit a higher form anisotropy the larger the value of A/app. Such increasing form anisotropy can be either due to increasing anisometry of the regions or-at a given anisometrydue to an increasing refractive index difference with the surrounding.The reasons for the appearance of some fairly longrange anisotropic structures in the PHEMA hydrogels have previously, in the first place, been traced to the amphiphilic nature of the polymer chain, which especially in water could lead to regions of micromesomorphic order.1 234 56Inhomogeneous cross-linking may be a second contributing factor, especially if water is present during network formation.The optical behavior can be qualitatively understood Scattering from a Spherical Domain Structure 433 in terms of a somewhat organized network containing cross-links and entanglements. Any cross-link or entanglement will restrict the long-range organization.The movement of entanglements during stress relaxation will change the interchain correlations, so that a restructuring will result. At small A/app the equilibrium optical behavior will approach the Gaussian behavior because the large number of cross-links disrupts the organizing tendency of the amphiphilic system.Acknowledgments. The financial support of the Syracuse University Research Institute is gratefully acknowleged. M. I. expresses his gratitude to the Institute of Macromolecular Chemistry, Czechoslovak Academy of Sciences, for granting a leave of absence, which made his postdoctoral stay in the U. S. possible. J. Hasa, Prague, has kindly cooperated in the preparation of the samples.
Hv light-scattering patterns from film specimens of relatively low density polyethylenes differ from the so-called "four leaf clover pattern" which is often found in the case of a well-grown spherulitic texture of polyethylene and can be derived from Stein's formulation of the scattered pattern. The pattern is some modifications removed from the "four leaf clover" pattern so as to have a rather long leafstalk, and may be called "four tennis rackets" arranged orthogonally. Some modifications of Stein's formulation for an isolated spherulite of a rather simple and regular anisotropy are proposed by taking the distribution of the size of spherulites into account, taking the spherulite anisotropy, (ar-at), as a function of distance from the center of the spherulite, and further making the boundary of the spherulite less clear. The former two modifications do not give any essential change in the scattering pattern from that predicted by the Stein's formulation, except for some shifts of the scattering angle at maximum intensity, while the latter modification gives the extension of the logarithmic contour plot of scattered intensity to lower scattering angles, and confirms the pattern of the "four tennis rackets." In addition, a modification of the spherulitic crystalline texture to a sheaf-like texture by using a two-dimensional symmetric sector model also gives an extension of the logarithmic contour plot to lower scattering angles, even showing the strongest scattered intensity at the lower angles when the sector angle is taken as less than 50°.
The calculation of the scattering from a sheaflike sector of a two‐dimensional spherulite has been carried out as a function of the apex angle of the sector. It is found that while for a complete spherulite the Hv scattered intensity is zero at zero scattering angle, there is an increasing intensity of scattering at 0° as the sector angle narrows. For very small values of the sector angle, the scattering becomes similar to that of a rod, with the exception that a scattering maximum is still seen at an angle close to that at which the spherulite scattering maximum occurs. The predictions of the model compare favorably with the scattering patterns observed for polymers in early stages of spherulitic growth.
Light scattering from oriented samples of crystalline polymers is affected by the birefringence of the sample. An extension of the theory for scattering from uniaxially deformed two‐dimensional and three‐dimensional spherulites is made so as to include the retardation of the incident and scattered beams in passing through the birefringent sample. Strain influences scattering, in that it changes the birefringence of the sample and it also changes the anisotropy and shape of the spherulites. Scattering intensities are calculated for both crossed and parallel polarizers as a function of Ω, χ, and Φ, where Ω is the angle between the stretching direction of the sample and the horizontal direction, and χ and Φ are the angles between the stretching direction and the polarization directions of the polarizer and analyzer, respectively. It is shown that for crossed polarizers with Φ = 45° and χ = 45° birefringence changes largely influence the results but that for the polarizers parallel at Φ = 0° and χ = 0° or crossed at Φ = 90° and χ = 0° the birefringence effect is minimized. The intensity distributions for crossed polarizers at Φ = 45° and χ = 45° from polyethylene films stretched to give retardations up to several wavelengths, are found to be in good agreement with the calculated results.
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