Nanostructured Polyelectrolyte Brushes

该提案描述了一个国际合作项目，重点研究聚电解质电刷，该项目涉及Christopher Ober（康奈尔大学）和j<s:1> rgen r<e:1> he（弗莱堡大学）的研究小组。聚（电解质）（PEL）电刷是特别有趣的，因为电荷的存在和由薄膜格式以及每条链的表面附着引起的几何约束，导致了这种系统的丰富的物理化学。由链拉伸引起的熵损失会对链与表面相连的键产生很强的拉力。最近有报道称，这种拉力在渗透刷中尤其强烈，以至于聚合物链的化学键断裂（链的熵死亡）。我们将探讨机械化学中这种相当不寻常的情况，在这种情况下，导致化学键断裂的机械力的起源不是外部的，而是内部的。我们计划通过生成精确定制组成的图案PEL刷来阐明这一点，其结构尺寸从无限（即均匀薄膜）到特征尺寸，其足迹与肿胀层厚度（即< 100 nm）相当。在前一种情况下，刷本质上代表两个二维结构，因为层只能通过从表面拉伸而膨胀，而后者允许更多的三维膨胀。我们计划解决以下关键问题：PEL电刷的膨胀是如何随着纳米结构的大小而扩大的，以及纳米结构中聚电解质电刷的限制如何影响链的稳定性以及与周围介质中离子的相互作用，这是环境、段/电荷分布和电荷状态的函数？为了研究这一点，我们计划从聚（苯乙烯磺酸盐）、季铵化聚（乙烯基吡啶）和聚（2-甲基丙烯氧基乙基三甲基氯化铵）中培养聚电解质刷，然后使用良性正交图案制造纳米结构刷。我们将使用基于同步加速器的方法，如x射线反射计、掠入射小角x射线散射（GISAXS）研究和近边缘x射线吸收精细结构（NEXAFS）来表征刷。此外，XPS和多角度椭偏仪将提供互补的信息，以及更常规的方法，如ATR-FTIR和SFM。因此，我们希望对PEL电刷的约束、膨胀和稳定性之间的复杂相互作用有更深入的了解，并对这类系统的复杂物理化学有新的认识。

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.