Strain Analysis of a Chiral Smectic A Elastomer

We present a detailed analysis of the molecular packing of a strained liquid crystal elastomer composed of chiral mesogens in the smectic A phase. X-ray diffraction patterns of the elastomer collected over a range of orientations with respect to the X-ray beam were used to reconstruct the three-dimensional scattering intensity as a function of tensile strain. For the first time, we show that the smectic domain order is preserved in these strained elastomers. Changes in the intensity within a given scattering plane are due to reorientation, and not loss, of the molecular order in directions orthogonal to the applied strain. Incorporating the physical parameters of the elastomer, a nonlinear elastic model is presented to describe the rotation of the smectic-layered domains under strain, thus providing a fundamental analysis to the mechanical response of these unique materials.Comment: 28 Page

Optimization of Patterson Map Correlation for Electron Density and Its Square: Relationships for Phase Extension and Refinement

An objective function is described for optimization of Patterson map correlation for electron density and its square. The function provides excellent discrimination against all zero phases, and is analyzed to find relationships for phase extension and refinement. The objective function and phasing relationships can be calculated rapidly by convolution methods and are practical for application to macromolecular structure determination problems. 1 Introduction We became interested in this project because the reported power of Debaerdemaeker & Woolfson's [1] phasing function y D = - å [ ] X Y h h h , (1) XMY hereafter, has not been adequately explained. XMY as a method of phase determination is based on maximizing y D by changing phases, one at a time. The phases are carried in X E E E h h k h k h k h k k = + + - - - - å | | cos( ) f f f , and (2) Y E E E h h k h k h k h k k = + + - - - - å | | sin( ) f f f , (3) where E E i h h h º | | exp{ } f is a (complex) normalized structur..