Dynamic Geometry and Kinetics of Polymer Confined in Self-Assembly via Cooperative Hydrogen Bonding: A Solid-State NMR Study under Paramagnetic Doping
Dynamic Geometry and Kinetics of Polymer Confined in Self-Assembly via Cooperative Hydrogen Bonding: A Solid-State NMR Study under Paramagnetic Doping
复制标题
通过协同氢键自组装限制聚合物的动态几何结构和动力学：顺磁掺杂下的固态核磁共振研究
DOI：
10.1021/ma100449n
复制
发表时间：
2010
期刊：
影响因子：
5.5
通讯作者：
Yongjin Li
中科院分区：
文献类型：
--
作者：
Toshikazu Miyoshi;Wei Hu;Yongjin Li
二级分子间相互作用的有序排列对于新材料的设计起着重要的作用，它导致了由具有不同尺寸和形状的多组分分子组成的独特的自组装。许多工作已经进入表征这种自组装系统的静态结构。1协同次级相互作用影响组分的分子动力学和整体性质。因此，理解微观动力学与自组装次级相互作用之间的关系是该领域的一个重要课题。2聚环氧乙烷（PEO）是一种氢受体，在甲醇溶液中能与氢供体脲形成超分子晶体。XRD显示，三分之二的UREA分子形成直径为0.1nm的纳米通道，其中包括孤立的PEO链和剩余的UREA分子（图1a）。3几个小组已经通过常规NMR弛豫测量研究了这种独特形态的PEO动力学，并提出PEO的动力学受到协同氢键的限制。4，5然而，PEO在该超分子体系中的分子动力学的几何和动力学的细节还没有很好地理解。利用磁各向异性相互作用的固态（SS）NMR技术不仅可以提供动力学，而且还可以提供分子动力学的几何。6.在过去十年中，开发了各种复杂的SS-NMR技术，以研究自然丰度中宽频率范围内的分子动力学。7-11其中，中心带仅检测交换（CODEX）7，8 NMR可以在缓慢范围内提供分子动力学的几何和动力学，并已成功应用于研究小分子，7聚合物，12-14液晶，15和聚合物共混物的分子动力学。16然而，这种稳健的技术受到低NMR灵敏度的影响，这限制了其在化学复杂系统和/或具有长T1 H值的系统中的应用。最近，Wickramasinghe等人提出了一种简单的方法，使用顺磁掺杂来增强灵敏度。17在蛋白质晶体中加入少量的顺磁性化合物可以有效地缩短T1 H值，而不会干扰结构。类似的策略可以适用于自适应系统。在本通讯中，CODEX NMR和顺磁掺杂已被用来阐明在天然丰度的PEO-UREA超分子系统中PEO的动态性质。图1a显示了PEOUREA超分子在213 K下的13 C CPMAS NMR谱及其结构。PEO在70 ppm处显示出非常尖锐的13 C信号。单共振支持
Well-defined arrangements of the secondary intermolecular interactions play important roles for the design of new materials, which leads to unique self-assemblies consisting of multicomponent molecules with different sizes and shapes. Much work has gone into characterizing the static structures of such selfassembled systems. 1 Cooperative secondary interactions influence the molecular dynamics of the components and the bulk properties. Therefore, understanding relationship between microscopic dynamics and secondary interactions in self-assemblies is an important subject in this field. 2 Poly (ethylene oxide)(PEO) is a hydrogen acceptor and can form supramolecular crystals with a small molecule of UREA, which is a hydrogen donor, in methanol solutions. XRD revealed that two-thirds of the UREA molecules form nanochannels with a diameter of∼ 1 nm, inside which isolated PEO chains and the remaining UREA molecules are included (Figure 1a). 3 Several groups have investigated PEO dynamics in this unique morphology by conventional NMR relaxation measurements and have suggested that the dynamics of PEO is restricted by cooperative hydrogen bonding. 4, 5 However, the details of the geometry and kinetics of the molecular dynamics of PEO in this supramolecular system are not well understood.Solid-state (SS) NMR techniques using magnetically anisotropic interactions can provide not only the kinetics and but also the geometry of the molecular dynamics. 6 In the past decade, various sophisticated SS-NMR techniques have been developed to investigate molecular dynamics in a wide frequency range in natural abundance. 7-11 Among them, center bands only detection of exchange (CODEX) 7, 8 NMR can provide both the geometry and kinetics of molecular dynamics in a slow range and has been successfully applied to investigate the molecular dynamics of small molecules, 7 polymers, 12-14 liquid crystals, 15 and polymer blends. 16 However, this robust technique suffers from low NMR sensitivity, which has limited its application in chemically complex systems and/or systems with long T1H values. Recently, Wickramasinghe et al. proposed a simple approach using paramagnetic doping for sensitivity enhancement. 17 Adding a small amount of a paramagnetic compound into a protein crystal could effectively shorten theT1H value without disturbing the structures. Similar strategies may be applicable to self-assemblied systems. In this Communication, CODEX NMR and paramagnetic doping have been used to elucidate the dynamic nature of PEO in a PEO-UREA supramolecular system in natural abundance. Figure 1a shows the 13C CPMAS NMR spectrum for PEOUREA supramolecules at 213 K and their structures. PEO shows a very sharp 13C signal at 70 ppm. The single resonance supports