Kinetics of aggregation in thermoresponsive polymer solutions upon a pressure jump

压力跃变时热响应聚合物溶液中的聚集动力学

• 批准号: 403786900
• 负责人: Professorin Dr. Christine M. Papadakis
• 金额: --
• 依托单位: Department of Physics
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2018
• 资助国家: 德国
• 起止时间: 2017-12-31 至 2022-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/403786900?language=en
• 关键词: Kinetics; aggregation; thermoresponsive; polymer; solutions

The research project planned addresses the relation between the hydration of thermoresponsive polymers in aqueous solution and the kinetics of their aggregation upon a pressure jump from the one-phase to the two-phase state. In dependence on temperature and pressure, non-ionic thermoresponsive polymers exhibit an elliptical coexistence line. It is well known that, at high pressure, the hydrophobic hydration of polymers at the phase transition decreases less than at atmospheric pressure. Moreover, the hydrogen bonds of the polar groups play an important role for the phase transition. Pressure jumps across the phase transition are an alternative to temperature jumps and offer the possibility to characterize the kinetics of aggregation and to relate it to the hydration state. In contrast to temperature jumps, also the early stages are accessible. Moreover, the dissolution of aggregates can be investigated in the reverse pressure jumps. At this, time-resolved measurements of the light transmission as well as time-resolved small-angle neutron and X-ray scattering are used. In addition, the interactions between polymer and water shall be investigated using Raman spectroscopy in dependence on temperature and pressure. Three systems are in the focus: (A) PNIPAM, (B) PNIPMAM, and (C) PS-b-PNIPAM diblock copolymers, all in aqueous solution. System A is a reference system, which we have investigated in numerous static investigations. System B features two-step behavior at the temperature-induced phase transition at atmospheric pressure, which is due to the enhanced hydrophobic interactions compared to PNIPAM. System C forms micelles with a thermoresponsive shell, and the results from system A can be applied to this self-assembled system. From the characterization of the aggregate growth, the growth mechanisms, the energy barriers and the collision times of the aggregates shall be determined and shall be related to the hydration. This way, a relation between the molecular interactions and the kinetics at mesoscopic length scales will be derived, which are applied to a more complex system.

该研究项目计划解决水溶液中热重点聚合物的水合与它们在压力从一相跳到两相状态时聚集的动力学之间的关系。在依赖温度和压力的情况下，非离子热响应聚合物表现出椭圆形共存线。众所周知，在高压下，聚合物在相变处的疏水水分降低的降低小于大气压下的疏水。此外，极性基团的氢键在相变为重要作用。在整个相变的压力跳跃是温度跳跃的替代方法，并提供了表征聚集动力学并将其与水合状态相关联的可能性。与温度跳跃相反，早期阶段也可以使用。此外，可以在反向压力跳跃中研究聚集体的溶解。在此，使用了时间分辨的光传输以及时间分辨的小角度中子和X射线散射。此外，应使用拉曼光谱法研究聚合物与水之间的相互作用，以依赖温度和压力。三个系统是重点：（a）PNIPAM，（b）PNIPMAM和（c）PS-B-PNIPAM二嵌段共聚物，都在水溶液中。系统A是一个参考系统，我们已经在众多静态研究中进行了研究。系统B在温度引起的大气压下的相变为两步行为，这是由于与PNIPAM相比的疏水相互作用增强所致。系统C与热弹壳形成胶束，系统A的结果可以应用于此自组装系统。根据骨料生长的表征，应确定骨料的生长机理，能屏障和碰撞时间，并应与水合有关。这样，将得出分子相互作用与介质长度尺度的动力学之间的关系，该关系应用于更复杂的系统。