Complex fluids in condensed matter: The liquid crystals

Liquid crystals are intermediate states in which matter can present itself, between the crystalline solid and the isotropic liquid. Materials that can present this type of state are made up of molecules, or aggregates of molecules, which present significant shape anisotropy. The liquid crystalline states present complex spatial structures, which pose fundamental questions in the study of the structure of matter. They are characterized by presenting some degree of order: long-range orientational and short-range positional. Its technological applications are diverse, in particular, the electro-optics (displays) with low energy consumption. In this article we present a review of this area, emphasizing lyotropic liquid crystals (formed by mixtures of amphiphilic molecules and solvent) that have a great interface with biological systems. We also discuss the theoretical models that describe phase diagrams of lyotropic nematic structures.液晶（Liquid Crystal）是介于结晶固体与各向同性液体之间的物质中间态。能够呈现此类状态的物质由分子或分子聚集体构成，其组分具有显著的形状各向异性。液晶态拥有复杂的空间结构，为物质结构研究带来了诸多基础性科学问题。这类物态的核心特征在于具备一定程度的有序性：长程取向有序与短程位置有序。其技术应用场景十分广泛，尤以低能耗的电光学（显示器件）应用最为典型。本文将对该研究领域展开综述，重点聚焦溶致液晶（lyotropic liquid crystals，由两亲分子与溶剂混合形成）——这类材料与生物系统具备极强的界面相容性。同时，本文还将探讨用于描述溶致向列相结构相图的理论模型。