Role of Non-Equilibrium Pinned Layers on the Thermodynamics of Confined Polymer Blends

这项工作将明智地结合实验和理论来探索固定聚合物层的作用，这是已知的在润湿基质上形成的，在受限聚合物混合物的表观热力学上。这项研究的动机是研究这个问题，因为最近使用各种互补工具对约束聚合物共混物的相行为进行的实验表明，相分离[“双节”]温度几乎不受约束的影响。这些结论在定性上与现有的平衡理论不一致，这些理论一致地预测了相混合态在约束下的强稳定。由于平衡情景似乎不能解释这些结果，因此推测实验结果源于一个众所周知的事实，即在可湿基质附近的熔体链在实验的时间尺度上有效地固定在该边界上。然后，自然地，剩余的非固定链的表观热力学受到这一固定层的影响，从而提供了一种使实验结果合理化的手段。这项研究将使用薄聚合物混合物和填充纳米颗粒的聚合物混合物来彻底探索这一猜测。小角中子散射和准弹性中子散射实验将与理论和模拟相结合，以描述这种钉住聚合物层的存在，并深入了解其对聚合物共混层相行为的影响。这些活动与两门新课程的开发紧密结合，名为“纳米材料导论”和“复杂流体的多尺度建模”，这两门课程将提供给大四本科生。PI还将与特洛伊的少年博物馆合作，开发IMAX风格的电影，针对K-12的儿童，关于聚合物的行为，特别是在表面附近。聚合物材料被用于无数的薄膜应用，如油漆、润滑剂、屏障涂层、纳米光刻和拟议的光电器件。本研究推测，在宏观时间尺度上的近表面层深刻地影响了受限聚合物的热力学性质。这些固定层也可以强烈地改变这些薄膜的结构，从而改变其机械、热学和电学性能。这些结论，如果得到验证，可能会影响聚合物在当前和未来各种应用中的设计和使用。教育和推广活动针对从幼儿园到高级毕业生的学生：这些活动将强调基础表面科学和聚合物在日常生活中的重要性

This work will judiciously combine experiments and theory to probe the role of pinned polymer layers, which are known to form at wetting substrates, on the apparent thermodynamics of confined polymer mixtures. This research is motivated to study this issue since recent experiments on the phase behavior of confined polymer blends, which utilize a variety of complementary tools, suggest that the phase separation ["binodal"] temperatures are hardly affected on confinement. These conclusions are in qualitative disagreement with existing equilibrium theories, which uniformly predict a strong stabilization of the phase mixed state on confinement. Since equilibrium scenarios do not appear to explain these results, it is conjectured that the experimental findings arise from the well known fact that melt chains in the immediate vicinity of a wettable substrate are effectively pinned to this boundary over the time scale of the experiments. It then naturally follows that the apparent thermodynamics of the remaining, non-pinned, chains are affected by the presence of this pinned layer, thus providing a means of rationalizing the experimental results. This research will use thin polymer mixtures and polymer blends filled with nanoparticles to exhaustively probe this speculation. Small angle neutron scattering and quasi-elastic neutron scattering experiments will be complemented with theory and simulations, to delineate the existence of this pinned polymer layer, and to incisively understand its consequences on the phase behavior of an overlayer of a polymer blend. These activities are strongly coupled to the development of two new courses, titled "Introduction to Nanomaterials" and "Multiscale Modeling of Complex Fluids," which will be offered to senior undergraduate students. The PI will also partner with the Junior Museum in Troy to develop IMAX style movies, aimed at K-12 children, on the behavior of polymers, especially in the vicinity of surfaces.%%%Polymeric materials find use in a myriad of thin film applications, such as paints, lubricants, barrier coatings, in nanolithography and in proposed optoelectronic devices. The proposed research conjectures that a near-surface layer, which is pinned on macroscopic time scales, profoundly affects the thermodynamic properties of confined polymers. These pinned layers could also strongly alter the structure and hence the mechanical, thermal and electrical properties of these thin films. These conclusions, if verified, could impact the design and use of polymers in these wide variety of current and future applications. The educational and outreach activities target students from kindergarten to the advanced graduate: these activities will stress the importance of fundamental surface science and polymers in everyday life.***