Solid-state NMR studies of polymers, liquid crystals and surfactants at surfaces and interfaces

我研究的主要主题是小分子和聚合物在表面和界面的动力学和结构性质的NMR研究。主要项目包括1）有机单层膜，2）纳米多层膜和3）纳米颗粒/液晶复合材料。广泛的表面和胶体表征技术与固体NMR结合使用，如表面红外光谱、光散射、光学显微镜、量热法和电泳。以前对有机单分子膜的研究建立了简单烷烃单分子膜的表面成键和链动力学。下一阶段将集中于其他分子和大分子与这些单层的结合。聚电解质是高度带电的聚合物。本文用固体核磁共振研究了强/强和强/弱聚阴离子/聚阳离子组合沉积在胶体基底上的多层膜的基本结构和动力学性质。我们现在将转移到基于氢键的多层膜，沉积在纳米颗粒上和作为中空胶囊。一个目标是了解胶囊对温度、pH或盐的响应（收缩与膨胀），这与它们用作药物递送剂有关。我们在液晶方面的初步工作集中在纳米二氧化硅填充液晶的“记忆效应”上，该液晶在显示设备中具有应用。这些材料最初是不透明的，但在电场中变得光学透明。由于有序二氧化硅网络的形成，这种状态在场关闭后仍然存在。人们对这种网络是如何形成的知之甚少。宽谱线氘核磁共振是分析这类结构的一种很好的方法。我们还将研究液晶/金属纳米颗粒复合材料。我们的目标将是创建一个有序的阵列，使光学特性可以通过应用领域进行调整。固体NMR将再次提供液晶分子在颗粒表面的排列的灵敏探针。

The major theme of my research is NMR studies of the dynamic and structural properties of small molecules and polymers at surfaces and interfaces. Main projects include 1) organic monolayers 2) polyelectrolyte multilayers and 3) nanoparticle/ liquid crystal composites. A large range of surface and colloidal characterization techniques are used in conjunction with solids NMR such as surface infrared spectroscopy, light scattering, optical microscopy, calorimetry and electrophoresis. Previous work on organic monolayers established the surface bonding and chain dynamics of simple alkane monolayers. The next stage will focus on the binding of other molecules and macromolecules to these monolayers. Polyelectrolytes are highly charged polymers. The basic structural and dynamic properties of polyelectrolyte multilayers consisting of stong/strong and strong/weak polyanion/polycation combinations deposited on colloidal substrates have been explored by solids NMR. We will now move onto multilayers based on hydrogen bonding, deposited on nanoparticles and as hollow capsules. One goal is to understand the response of the capsules (shrinking versus swelling) to temperature, pH or salt which is relevant to their use as drug delivery agents. Our initial work on liquid crystals has focused on the "memory effect" of nanoparticle silica filled liquid crystals which have applications in display devices. These materials are initially opaque but become optically transparent in an electric field. This state persists after the field is turned off due to the formation of an ordered silica network. How such networks form is poorly understood. Wideline deuterium NMR is an excellent method for analyzing such structures. We will also study liquid crystal/ metal nanoparticle composites. The goal will be to create an ordered array so that the optical properties can be tuned by an applied field. Solids NMR will again provide a sensitive probe of the the alignment of the liquid crystal molecules at the particle surfaces.