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上的动态和结构性质的核磁共振研究。主要项目包括1)有机单分子膜，2)聚电解质多层膜，3)纳米粒子/液晶复合材料。大量的表面和胶体表征技术与固体核磁共振技术结合使用，如表面红外光谱、光散射、光学显微镜、量热和电泳。以前关于有机单分子膜的工作建立了简单烷烃单分子膜的表面键合和链动力学。下一阶段将专注于其他分子和大分子与这些单分子膜的结合。聚电解质是高度带电的聚合物。用固体核磁共振技术研究了胶体衬底上由强/强和强/弱聚阴离子/聚阳离子组合组成的聚电解质多层膜的基本结构和动力学性质。我们现在将转向基于氢键的多层膜，即沉积在纳米颗粒上的中空胶囊。一个目标是了解胶囊(收缩和膨胀)对温度、pH或盐的反应，这与它们作为药物递送剂的使用有关。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，这些纳米颗粒填充液晶在显示设备中有应用。这些材料最初是不透明的，但在电场中变得光学透明。在由于形成有序的二氧化硅网络而导致场关闭之后，这种状态持续存在。人们对这种网络是如何形成的知之甚少。宽线氘核磁共振是分析这种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。目标是创建一个有序的阵列，以便可以通过外加电场来调节光学特性。固体核磁共振将再次为液晶分子在颗粒表面的排列提供灵敏的探针。

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.