Presidential Young Investigator Award: Sub-Triple Liquids and Crystallization in Supercritical Fluids

亚三重液体（低于其三相点的亚稳液体）：该项目包括一项涉及同时沸腾和结晶的相变（亚三重液体特有）的实验研究，完成一项拉伸不稳定性（拉伸强度损失）的理论研究，以及密度异常（加热时收缩的液体）的分子起源的研究。通过PI推导了拉伸不稳定性与密度异常之间的联系。超临界流体结晶：这部分项目包括完成设备建设和初步实验，在该实验中，连续沉淀成为温度、压力和成分可独立操纵的流体。新奇/创新：亚三重液体是一种未被探索的物质状态（这个术语是由PI创造的）。它们的行为包括拉伸不稳定性（抗拉强度随着温度降低而降低，实验观察到的异常首先由PI解释）和涉及快速结晶和沸腾以及液体消失的相变，这是自然界中其他地方没有发现的现象。超临界流体结晶是制备均匀结晶和单分散聚合物颗粒的一种新方法。这个项目中最具创新性的概念是在流体中通过控制压力而不是温度来实现均匀、可控的成核条件。压力扰动以声速传播，从而保证了整个流体介质的均匀性，并应用于接近其临界点的高度可压缩流体，从而引起密度和溶剂功率的大变化。技术影响/实际意义：当脱气液体在刚性容器内冷却时产生的张力非常适合于平面粘附性的无损检测。这是一个在微芯片制造中至关重要的问题（例如，光抗蚀剂粘合测试）。实验观察到的亚三重液体和晶体的平衡提出了创造均匀受力固体的新想法。由于不可能使固体受到各向同性张力，因此该过程（张力结晶）可能导致生产具有独特性能的材料。

Research Summary: Sub-triple liquids (metastable liquids below their triple point): This project includes an experimental study of the phase transition (unique to sub-triple liquids) involving simultaneous boiling and crystallization, completion of a theoretical study of tensile instability (loss of tensile strength), and investigation of the molecular origin of density anomalies (liquids which contract when heated). The connection between tensile instability and density anomalies was derived by the PI. Crystallization in supercritical fluids: This portion of the project involves completion of equipment construction and preliminary experiments in which continuous precipitation occurs into a fluid whose temperature, pressure, and composition can be independently manipulated. Novelty/Innovation: Sub-triple liquids are an unexplored state of matter (the term was coined by the PI). Their behavior includes tensile instabilities (a decrease in tensile strength as the temperature is lowered, an experimentally observed anomaly first explained by the PI) and a phase transition involving rapid crystallization and boiling coupled with liquid disappearance, a phenomenon not to be found elsewhere in nature. Crystallization from supercritical fluids is a novel method for the production of uniform crystals and monodisperse polymer particles. The most innovative concept in this project is the attainment of uniform, controllable conditions within the fluid where nucleation occurs through a manipulation of pressure instead of temperature. Pressure perturbations travel at the speed of sound, thus guaranteeing uniformity throughout the fluid medium and are applied to a highly compressible fluid near its critical point, thus giving rise to large changes in density and hence solvent power. Technical Impact/Practical Significance: Tension generated when a degassed liquid is cooled inside a rigid container is ideally suited for the non-destructive testing of adhesion on flat surfaces. This is a problem of vital importance in microchip manufacture (e.g., photo-resist adhesion testing). The experimentally observed equilibrium of a sub-triple liquid and a crystal suggests the novel idea of creating solids which are uniformly stressed. Since it is otherwise impossible to subject a solid to isotropic tension, this process (tension crystallization) could lead to the production of materials with unique properties.