Department SIMAU, Università Politecnica delle Marche, Ancona, Italy.
Department Medical Biotechnology and Translational Medicine, Università di Milano, Milano, Italy.
Sci Rep. 2017 Jul 10;7(1):4959. doi: 10.1038/s41598-017-05136-z.
Throughout the whole history of liquid crystals science, the balancing of intrinsic elasticity with coupling to external forces has been the key strategy for most application and investigation. While the coupling of the optical field to the nematic director is at the base of a wealth of thoroughly described optical effects, a significant variety of geometries and materials have not been considered yet. Here we show that by adopting a simple cell geometry and measuring the optically induced birefringence, we can readily extract the twist elastic coefficient K of thermotropic and lyotropic chiral nematics (N*). The value of K we obtain for chiral doped 5CB thermotropic N* well matches those reported in the literature. With this same strategy, we could determine for the first time K of the N* phase of concentrated aqueous solutions of DNA oligomers, bypassing the limitations that so far prevented measuring the elastic constants of this class of liquid crystalline materials. The present study also enlightens the significant nonlinear optical response of DNA liquid crystals.
纵观液晶科学的整个历史，内在弹性与外部力量耦合的平衡一直是大多数应用和研究的关键策略。虽然光场与向列型指向矢的耦合是丰富的、经过充分描述的光学效应的基础，但仍有大量的几何形状和材料尚未被考虑。在这里，我们展示了通过采用简单的池体几何形状并测量光致双折射，我们可以轻松提取热致和溶致手性向列相（N*）的扭曲弹性系数 K。我们获得的 K 值对于手性掺杂 5CB 热致 N与文献中报道的值非常吻合。通过相同的策略，我们首次确定了 DNA 低聚物浓水溶液中 N相的 K 值，克服了迄今为止阻碍测量此类液晶材料弹性常数的局限性。本研究还阐明了 DNA 液晶的显著非线性光学响应。
