Staged phase separation in the I–I–N tri-phase region of platelet–sphere mixtures

Abstract

Mixtures of colloids with different sizes or shapes are ubiquitous in nature and extensively applied in industries. Phase transition pathways and kinetics in this model system should be investigated because of the difficulty in observing tri-phase coexistence in colloidal platelet-sphere mixtures. Similar to the polymer-sphere mixtures, the phase transition pathway has three main categories. Analytical results show a staged phase transition process in which the mixture first separates into one or two metastable phases, then further separates, and subsequently reaches tri-phase equilibrium. Unique to our system, and different from the gas-liquid-crystal coexistence in colloid-polymer mixtures, the platelet-sphere mixture reached a gas-liquid-liquid crystal (nematic) coexistence. Thus, the different phases are easy to distinguish using the birefringence of the liquid crystals. In addition, the volume fraction of the liquid crystal formation in the ZrP platelet suspensions is much lower than for the crystal formation in hard spheres.

Swelling Inhibition of Liquid Crystalline Colloidal Montmorillonite and Beidellite Clays by DNA

“…Somewhat similar observations were recently made with a system that consists in α-ZrP nanoplates of 700 nm diameter and silica spheres of 160 nm diameter. In addition, the different demixtion pathways of triphasic systems were determined 29 . Moreover, mixtures of beidellite clay nanosheets of 200 nm diameter and 0.7 nm thickness and small silica spheres of 22 nm diameter displayed some stabilization of the nematic phase with respect to the isotropic one, together with some weakening of the viscoelastic properties 30 .…”

Dispersions of α-Zirconium Phosphate/organic Solvent with Structural Colors

“…剥离后的 α-ZrP 粒子表面仍带负电荷 [15] , 这说明其表面的磷酸根负离子部分与 TBA ＋ 离子发生配 对, 剩余的 TBA ＋ 离子作为反荷离子在 α-ZrP 纳米片周 围形成双电层. 由于 α-ZrP 片层间存在比较强的静电排 斥作用, 使得 α-ZrP 纳米片在水中可以发生有序排 列 [10,11,13] .…”

“…这表明除了片层的表面 电荷性质以外, 纳米片层的尺寸对光子液晶材料的形成 也有显著的影响. 片层的直径越小, 由于有序排列带来 的能量补偿越少, 因而在浓度减小时越难继续保持其有 序结构 [11,13] .…”

“…为了制备 α-ZrP 的纳米分散体系, 研究者多是利用 季铵盐, 如四丁基氢氧化铵(TBAOH, 分子结构式如图 式 1c 所示)对 α-ZrP 进行插层, 并在水溶液中发生剥离, 所得 α-ZrP/H 2 O 分散体系易形成液晶相 [9][10][11] , 但从未在 此类体系中观察到结构色现象. 在我们的实验中, 原计 划对已经剥离后的 α-ZrP/H 2 O 利用多次离心沉淀后再分 散, 同时进行溶剂置换的方法制备 α-ZrP 的有机溶剂分 散体系.…”

Defect-mediated colloidal interactions in a nematic-phase discotic solvent

“…[38][39][40] A recent experimental breakthrough made it possible to achieve the nematic phase in a discotic system, at room temperature, with gold nanoparticles. 41 A handful of studies have also focused on phase transitions, [42][43][44][45][46][47][48][49][50][51][52] kinetic behavior, 48 segregation, [53][54][55] and sedimentation 56 of colloid-discotic mixtures.…”