A study on hydrogen-bonded network structure of polybenzoxazines

The hydrogen-bonded network structure for polybenzoxazines is investigated by Fourier Transform Infrared Spectroscopy (FT-IR) with model dimer systems. Comparing the FT-IR spectra of the polybenzoxazines and model dimers, it is shown that the simpler structures of asymmetric dimers well simulate the hydrogenbonded network structure between polymer chains while the structures of symmetric dimers reflect the hydrogen bonding scheme related to the end-cups of polymer chains. It is confirmed that the amine functional group in the Mannich bridge is greatly responsible for the distribution of hydrogen bonding species. Bisphenol A/methylamine-based polymer (BA-m) mainly consists of -(OHN)-N-... intramolecular hydrogen bonding while bisphenal A/aniline-based polymer (BA-a) has a large amount of intermolecular hydrogen bonding and relatively weak hydrogen bonding groups in the polymer network structure. The possible network structure, in the sense of hydrogen bonding, for BA-m and BA-a polymers is proposed and a generalized explanation for the structure-property relationships in polybenzoxazines is also discussed.