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.

该研究项目计划研究水溶液中热敏聚合物的水合与其在压力从一相状态跃升至两相状态时聚集的动力学之间的关系。根据温度和压力，非离子热敏聚合物表现出椭圆形共存线。众所周知，在高压下，聚合物在相变时的疏水水合作用比在大气压下减少得更少。此外，极性基团的氢键对于相变起着重要作用。相变过程中的压力跃变是温度跃变的替代方案，并提供了表征聚集动力学并将其与水合状态联系起来的可能性。与温度跳跃相比，早期阶段也是可以进入的。此外，可以在反向压力跳跃中研究聚集体的溶解。此时，使用光透射的时间分辨测量以及时间分辨小角中子和 X 射线散射。此外，应使用拉曼光谱研究聚合物和水之间的相互作用与温度和压力的关系。重点关注三个系统：(A) PNIPAM、(B) PNIPMAM 和 (C) PS-b-PNIPAM 二嵌段共聚物，均在水溶液中。系统 A 是一个参考系统，我们在大量静态调查中对其进行了研究。系统 B 在大气压下温度诱导的相变中具有两步行为，这是由于与 PNIPAM 相比疏水相互作用增强。系统 C 形成具有热响应外壳的胶束，系统 A 的结果可以应用于该自组装系统。根据骨料生长的特征，应确定骨料的生长机制、能垒和碰撞时间，并与水合作用有关。这样，将导出介观长度尺度上分子相互作用和动力学之间的关系，并将其应用于更复杂的系统。