Algebraic dependence of the structure factor and possible anharmonicity in a high-resolution x-ray study of a side-group polymeric liquid crystal.

摘要: We report on a high-resolution x-ray study of the smectic-A phase near nematic\char21{}smectic-A transition side-group polymeric liquid crystal, polyacrylate. Except at very vicinity transition, first- and second-harmonic structure factors were found to be consistent with harmonic theory de Gennes Caille. However, close attempts fit two harmonics completely failed. believe that this is evidence for importance anharmonic corrections transition. The fits experimental data yield compressibility constant B splay elastic ${\mathit{K}}_{\mathit{s}}$. can described by power law B\ensuremath{\sim}${\mathit{t}}^{\mathrm{\ensuremath{\varphi}}}$, where t=(${\mathit{T}}_{\mathit{c}}$-T)/${\mathit{T}}_{\mathit{c}}$,${\mathit{T}}_{\mathit{c}}$ being phase-transition temperature. \ensuremath{\varphi} was 0.82\ifmmode\pm\else\textpm\fi{}0.08, in good agreement theoretical predictions using exponents from literature, but disagreement previous results monomeric crystals. ${\mathit{K}}_{\mathit{s}}$ has roughly same magnitude as crystals tends decrease approximately 50% upon approaching below. This temperature dependence further anharmonicity system.