Direct observation of polymer network structure by TEM

聚合物网络体系是一种典型的非晶态体系，利用光子、x射线和中子等散射技术对其进行了大量的结构研究。然而，讨论或多或少地局限于远距离排序，详细结构仍有待阐明。本研究旨在通过透射电子显微镜（TEM）对聚合物网络结构进行直接观察，这是一项非常雄心勃勃的试验，因为这种观察仅限于高度结晶的聚合物，而不是非晶态的聚合物。作为TEM观察的样品，聚硅氧烷网络，引入苯基以改善电子束电阻的聚硅氧烷网络，含有芳香中间体的液晶弹性体，掺杂无机盐的聚氧乙烯网络，以及离子聚醚弹性体。使用本基金购买的显微切片机，在室温或较低温度（液氮温度或干冰温度）下制备这些聚合物样品的超薄膜（厚度100-300 nm）。在这些薄样品上，通过低温技术和/或氧化钌染色技术进行了多次透射电镜测量。然而，所有的试验都未能直接观察到网络结构。用透射电子显微镜观察了天然橡胶在拉伸条件下的结晶图和电子衍射图，以及聚醚的结晶片。然而，这些都是在无定形基体中形成的晶体结构，而不是网状结构。考虑到苯基是无效的，我们必须考虑制备更耐药的聚合物网络，或者找到另一种方法来观察透射电镜，以达到我们最初的目的。

Polymer network systems are a typical amorphous system, and many structural studies on them have been conducted by scattering techniques using photon, X-ray and neutron. However, the discussions are more or less limited on long-distance orderings, and the detailed structures are still to be elucidated.This study aimed to conduct direct observations of polymer network structures by transmission electron microscopy (TEM), which was very ambitious trial because such observations were limited on highly crystalline polymers, never on amorphous ones.As samples for the TEM observation, poly(siloxane) networks, those introduced phenyl groups for improving electron-beam resistance, liquid crystalline elastomers containing aromatic mesogens, poly(oxyethylene) networks doped with inorganic salts, and ionic polyether elastomers. Using microtome, which was purchased by this funding, the ultrathin films of these polymer samples (thickness ; 100-300 nm) were prepared at room temperature or at lower temperatures (liquid nitrogen temperature or Dry-ice temperature).On these thin samples TEM measurements by cryo-techniques and/or staining technique using ruthenium oxide were carried out for many times. However, all trials failed to directly observe the network structure. We managed to observe crystalline emages of natural rubber under extension by TEM together with the electron diffraction patterns, and crystalline lamellae of polyethers. However, these are all crystalline structures formed in the amorphous matrix, not the network structure. Taking account that phenyl groups were not effective, we have to consider preparing much more resistant polymer networks or figuring out another methods of TEM observation far our initial purpose.