Materials World Network: Controlling Properties of Polymers in Thin Films

这个材料世界网络汇集了世界上在聚合物薄膜实验表征方面的专家（分别是美国波士顿大学和Universität Freiburg， Freiburg, Freiburg，德国的薄膜应力和粘弹性方面的专家）和在受限聚合物的动力学和结构方面的计算机模拟专家(Institut Charles Sadron, Strasbourg；（法国）寻求一种统一图景的可能性，这种图景可以解释迄今为止观察到的聚合物薄膜的所有不寻常性质（即动力学、残余应力和热膨胀性），同时试图将这些性质与其中的（非平衡）聚合物结构以及制造和/或制造后生产过程联系起来。通过建立这种结构-性能和加工-性能关系，网络的目标是最终建立一种可以预测、设计和调整聚合物薄膜性能的策略。由于聚合物薄膜的结构是亚稳态的，并且随着时间的推移而改变，因此使用交联聚苯乙烯共聚物来冻结结构，从而冻结其特性。这项研究在很大程度上受到几个已发表的实验和Reiter（来自德国的PI）和de Gennes推测的模型的指导，该模型描述了快速溶剂蒸发产生的非平衡聚合物网络结构如何解释负热膨胀率。该程序的结果有望证实该模型，并进一步扩展其与薄膜动力学行为的相关性。由此产生的更全面的模型将提供一个关键的平台，在这个平台上可以描绘和/或制定结构-属性和处理-属性关系。聚合物薄膜的应用非常广泛。该计划的成功导致了一个简单的策略来设计和制造具有预先热膨胀和/或动态特性的聚合物薄膜。拥有这样的能力大大提高了我们的杠杆作用，使这些材料以具有成本效益的方式适应应用程序对其性能不断变化的要求。该项目培养了六名博士生，为他们提供了一个很好的训练基地，以解决有关自旋涂覆聚合物薄膜的特殊性能的学术挑战和技术相关问题。该网络的成员受益于该计划的国际环境。特别是，除了频繁的视频会议外，博士生之间还有定期的会议和身体交流。该项目积极吸引本科生和高中生参与。该奖项由DMR聚合物项目和DMR特别项目办公室共同资助。

This Materials World Network brings together world-expertise on the experimental characterizations of polymer films (Boston University, USA and Universität Freiburg, Freiburg, Germany on the film stress and viscoelasticity, respectively) and computer simulations on the dynamics and structure of confined polymers (Institut Charles Sadron, Strasbourg, France) to seek for the possibility of a unified picture that can account for all the unusual properties observed of polymer films to date (namely the dynamics, residual stress and thermal expansivity), and at the same time attempt to relate these properties to the (out-of-equilibrium) polymer structures therein as well as the fabrication and/or post-fabrication processes producing them. By establishing such structure-property and processing-property relations, the Network aims to ultimately institute a strategy that can predict, design and tune the properties of polymer films. Because the structures of the polymer films that allegedly cause the unusual properties are metastable and change with time, a cross-linkable copolymer of polystyrene are used to freeze-in the structures and whereby their properties. This research is largely guided by several published experiments and a model conjectured by Reiter (the PI from Germany) and de Gennes portraying how a non-equilibrated polymer network structure engendered by rapid solvent evaporation could explain negative thermal expansivity. The results of this program are expected to substantiate this model, and additionally expand its relevance to the dynamical behaviors of the films. The resultant, more encompassing model will provide a pivotal platform upon which the structure-property and processing-property relations can be portrayed and/or formulated.Applications of polymer films are widespread. Success of this program leads to a simple strategy to design and fabricate polymer films with premeditated thermal expansion and/or dynamical properties. Having such ability significantly enhances our leverage to adapt these materials in a cost effective manner to the ever-changing demands on their properties by the applications employing them. Six PhD students are trained in this program, providing them an excellent training ground in the academically challenging and technologically relevant problem concerning the unusual properties of spin-coated polymer films. Members of the Network benefit from the international setting of the program. In particular, there are regular meetings and physical exchange between the PhD students besides frequent video conferences. This program actively engages undergraduate and high-school student participants. This award is jointly funded by the DMR Polymers Program and the DMR Office of Special Programs.