Solid-State NMR for Polymeric Nanoparticles

聚合物纳米颗粒的固态核磁共振

• 批准号: 0097202
• 负责人: Jacob Schaefer
• 金额: $ 42万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-03-01 至 2004-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0097202&HistoricalAwards=false
• 关键词: Solid; State; NMR; Polymeric; Nanoparticles

The primary goal of the proposed new work is the application of solid-state NMR to the characterization of three types of polymeric nanostructures: (1) hyperbranched polycarbonates, (2) dendritic poly(benzyl ether)s, and (3) cross-linked amphiphiles of nanoscale dimensions with a core-shell morphology. The principal technique to be used to solve all three problems will be stable-isotope labeling with rotational-echo double-resonance (REDOR) detection. This strategy involves two or more stable-isotope labels ( or sometimes one label and C-13 at natural abundance) that are incorporated in or near the region of interest, which might be an interface, or a core or surface site of the nanoparticle. REDOR then detects the dipolar coupling between heteronuclear pairs of spins. The coupling is directly related to an inferred if the averaging effects of motion are absent or suppressed. The first research goal is to use C-13/H-2 REDOR to compare the chain packing in linear phenol-polycarbonate with that in hyperbranched polycarbonate of identical chemical composition. Preliminary results indicate a considerable degree of local order in the chain packing of the linear system. REDOR will establish the extent to which this order persists in the presence of 50% branching. The second research goal is to use C-13/F-19 REDOR to establish the packing of chain ends within the internal architecture of a dendrimer, and to determine the extent of interpenetration of chain ends between dendrimers. The stable-isotope labeled dendrimers will be imbedded within a matrix composed either of other dendrimers or of polystyrene, the latter to form a blend interface. The third research goal is to use C-12, N-15, H-2 and F-19 labels in various combinations for the core, interface, and shell of amphiphilic core-shell nanostructures so that multi-frequency REDOR can identify proximities at interfacial, cross-link, and surface sites. These proximities will be used to generate structural models that help interpret chemical, biochemical, and mechanical properties, and to suggest strategies for the synthesis of more effective materials.%%%Dendrimers and hyperbranched polymers are valued for their low melt viscosity, high solubility, and the possibility of many surface-active functional groups. They can be used as encapsulants, ultra-thin film coatings, and as nanoscale filler particles in polymeric composites. Individual molecules form discrete nanostructures with few intermolecular entanglements and many of the other properties of more mechanically stable nanoparticles. Nanostructured amphiphiles mad by cross-linking micelles formed from from block copolymers are true nanoparticles whose proposed applications of societal importance are vast ranging form environmental clean-up, to biomedical drug delivery, to functionalized surfaces to support tissue growth. Whether any of these nanoscale polymer applications will actually succeed will depend on the ability of synthetic chemists to control structure at the atomic level. This structure depends largely on how polymer chains pack within and on the nanoparticle. The characterization of chain packing, cross-linking, and the spatial distribution of functional groups by solid-state NMR is sufficiently detailed that the directed synthesis of tailored nanostructures will be practical.

提出的新工作的主要目标是应用固态NMR表征三种类型的聚合物纳米结构：（1）超支化聚碳酸酯，（2）树枝状聚（苄基醚），和（3）具有核-壳形态的纳米尺度的交联两亲物。 用于解决所有这三个问题的主要技术将是稳定同位素标记与旋转回波双共振（REDOR）检测。 该策略涉及两个或更多个稳定同位素标记（或有时一个标记和天然丰度的C-13），其被掺入到感兴趣的区域中或附近，所述感兴趣的区域可以是纳米颗粒的界面或核心或表面位点。 然后，REDOR检测异质自旋对之间的偶极耦合。 如果运动的平均效应不存在或被抑制，则耦合与推断直接相关。 第一个研究目的是利用C-13/H-2REDOR比较线性苯酚聚碳酸酯和相同化学组成的超支化聚碳酸酯的链堆积。 初步结果表明，在相当程度的局部秩序的线性系统的链包装。 REDOR将确定在存在50%分支的情况下该顺序持续的程度。 第二个研究目标是使用C-13/F-19 REDOR来建立树状聚合物内部结构内链端的包装，并确定树状聚合物之间链端的相互渗透程度。 稳定同位素标记的树枝状聚合物将嵌入由其他树枝状聚合物或聚苯乙烯组成的基质中，后者形成共混界面。 第三个研究目标是使用C-12，N-15，H-2和F-19标签的各种组合的核心，界面和两亲性核壳纳米结构的外壳，使多频REDOR可以识别在界面，交联和表面位点的邻近性。 这些接近性将用于生成结构模型，以帮助解释化学，生物化学和机械特性，并为合成更有效的材料提出策略。树枝状聚合物和超支化聚合物因其低熔体粘度、高溶解性和许多表面活性官能团的可能性而具有价值。 它们可用作澄清剂、超薄薄膜涂层和聚合物复合材料中的纳米级填料颗粒。 单个分子形成离散的纳米结构，具有很少的分子间缠结和更多机械稳定的纳米颗粒的许多其他性质。 通过由嵌段共聚物形成的交联胶束而产生的纳米结构的两亲物是真正的纳米颗粒，其提出的具有社会重要性的应用范围广泛，从环境净化，到生物医学药物递送，到功能化表面以支持组织生长。 这些纳米级聚合物的应用是否会真正成功，将取决于合成化学家在原子水平上控制结构的能力。 这种结构在很大程度上取决于聚合物链如何在纳米颗粒内和纳米颗粒上堆积。 链包装，交联，和空间分布的功能基团的固态NMR的表征是足够详细的定制的纳米结构的定向合成将是实用的。