Polyacrylonitrile (PAN) is an important industrial polymer material because it is precursor for carbon fiber. Heat-treatment induces strucutral change from linear polymer chains to three dimensional carbon materials which determine final mechanical properties for carbon fibers. Characterization of complex chemical reaction has been conducted by various characterization techniques. However, detailed structures have not been accesible due to insolubility of chemically reacted samples. In this presentation, we will present intramolecular and intermolecular chemical reactions of PAN and its copolymer (PAI) with itaconic acid by using 13C isotope labeling and solid state NMR. Even using isotope labeled sample, it is challenging to capture chemical strucutre of the reacted sample in the very early stage. Sensitivity enhanced DNP nmr is used to solve the sensitivity problem. Moreover, we will address advantage and disadvantage of applicatin of DNP nmr in polymer characterization.
