Parabanic polymers obtained by the cyclocondensation reaction of polyureas containing 2,6-pyridyl structure

The polymers containing 1,3-imidazolidine-2,4,5-trione rings on the macromolecular backbone are known for a few years and named poly(parabanic acid)s. The paper presents some polymers and model compounds with urea and/or parabanic structures, as a result of the cyclocondensation reaction of the urea derivatives containing 2,6-pyridyl rest, with the oxalyl chloride. The 2,6-pyridyl radical has an acid acceptor character that determines an important distinct influence on the cyclocondensation reaction. The influence of the reaction conditions (temperature, time, beside of the presence or absence of pyridine (Py)) on the progress of the cyclocondensation was studied. The advance of the reaction was followed by IR spectra. The products were characterized by the elemental analysis, 1H NMR and IR spectra, solubilities and viscosity measurements. Thermal properties were determined by thermogravimetric analyses and differential scanning calorimetry. The analytical and spectral data demonstrated that, in absence of Py, the cyclocondensation performed almost completely only in the case of the aliphatic polyureas, while, in the same conditions, the aromatic polymers were only partly transformed. By using the Py as catalyst, both aromatic and aliphatic polyureas can be transformed into parabanic polymers at above 90% transformation degree (TD). A calculation method of the TD based on the IR spectroscopy was discussed.