Direct observation of polymer network structure by TEM

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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.