Nanostructured Polyelectrolyte Brushes

该提案描述了一个专注于聚电解质电刷研究的国际合作项目，该项目由Christopher Ober(康奈尔大学)和Jürgen Rühe(弗莱堡大学)的研究小组参与。聚(电解液)(PEL)刷子特别令人感兴趣，因为电荷的存在以及薄膜形式和每个链的表面附着所产生的几何约束，导致了此类体系的丰富的物理化学。链拉伸引起的熵损失会对链连接到表面的键产生非常强大的拉力。最近有报道称，渗透刷子中的拉力特别强，以至于聚合物链的化学键发生断裂(链的熵死亡)。我们将探索这一相当不寻常的机械力化学案例，在这种情况下，导致化学键断裂的机械力的来源没有外部原因，而是内部来源。我们计划通过生成精确定制的图案化PEL刷子来阐明这一点，其结构尺寸从无限大(即均匀薄膜)到特征尺寸，其足迹与膨胀的层厚度(即&lt；100 nm)相当。在前一种情况下，笔刷基本上代表两个2D结构，因为层只能通过拉伸远离表面来膨胀，而后者允许更多的3D膨胀。我们计划解决以下关键问题：PEL刷子的膨胀如何与纳米结构的尺寸成比例，以及聚电解质刷子在纳米结构中的限制如何影响链的稳定性以及作为环境、链段/电荷分布和电荷状态的函数与周围介质中的离子的相互作用？为了研究这一点，我们计划以聚(苯乙烯磺酸盐)、季节化的聚(乙烯基吡啶)和聚(2-甲基丙烯氧基乙基三甲基氯化铵)为原料生长聚电解质刷，然后使用良性的正交图案来创建纳米结构的刷。我们将使用基于同步加速器的方法来表征刷子，例如X射线反射仪、掠入射小角X射线散射(GISAXS)研究和近边X射线吸收精细结构(NEXAFS)。此外，XPS和多角度椭偏测量法以及ATR-FTIR和SFM等常规方法都将提供补充信息。因此，我们希望对PEL刷子的限制、膨胀和稳定性之间的复杂相互作用有更深入的了解，并对此类体系的复杂物理化学有新的见解。

This proposal describes an international collaborative program focused on the study of polyelectrolyte brushes that involves the research groups of Christopher Ober (Cornell University) and Jürgen Rühe (University of Freiburg). Poly(electrolyte) (PEL) brushes are of particular interest because the presence of charges and the geometric constraints arising both from the thin film format as well as from the surface attachment of each chain, lead to a rich physical chemistry of such systems. The loss of entropy induced by chain stretching generates a very strong pull on the bonds through which the chains are linked to the surface. It has recently been reported, that the pull can be especially in osmotic brushes so very strong that breaking of chemical bonds of the polymer chain occurs (entropic death of the chains). We will explore this rather unusual case of mechanochemistry, where the origin of the mechanical forces leading to rupture of chemical bonds has no external, but an internal origin. We plan to elucidate this by generating patterned PEL brushes of precisely tailored composition with structure sizes from infinite (i.e. homogenous thin film) down to feature sizes whose footprints are comparable to the swollen layer thickness (i.e. < 100 nm). In the former case the brushes represent essentially two 2D- structures as the layer can only swell by stretching away from the surface while the latter allows a more 3D-swelling. We plan to address the following key questions: How does the swelling of the PEL brushes scale with size of the nanostructure and how does confinement of polyelectrolyte brushes in nanostructures influence chain stability and the interaction with ions in the surrounding medium as a function of environment, segment/charge distribution and charge state? To study this, we plan to grow polyelectrolyte brushes from poly(styrene sulfonate), quaternized poly(vinyl pyridine) and poly(2-methacryloxyethyl trimethylammonium chloride) and then create nanostructured brushes using benign orthogonal patterning. We will characterize the brushes using synchrotron-based methods such as X-ray reflectometry, grazing incidence small angle X-ray scattering (GISAXS) studies and near edge X-ray absorption fine structure (NEXAFS). In addition both XPS and multiple angle ellipsometry will provide complementary information, as will more routine methods such as ATR-FTIR and SFM. As a result we hope to obtain a deeper understanding of the complex interplay between confinement, swelling and stability of PEL brushes and obtain new insights into the complex physicochemistry of such systems.