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High and low molar mass compounds containing the 3-alkyl-1,4-diaryIpentazadiene group were synthesized in the reaction of aromatic diazonium salts with primary amines. These high nitrogen compounds are characterised by high photosensitivity and thermostability. The photolytic decomposition was studied in detail with respect to the substitution at the aromatic moieties and at N3 of the pentazadiene chromophore. Electron donating aromatic substituents were found to increase photosensitivity and decrease thermostability whereas electron withdrawing aromatic substituents cause higher photolytic and thermolytic stability. A little influence of the alkyl group at N3 on the photosensitivity of the pentazadiene group was observed. Photolysis was investigated by means of UV/Vis spectroscopy and obeys first order kinetics for some compounds under investigation. Gel permeation chromatography (GPC) measurements during photolysis of pentazadiene polymers prove that irradiation with UV light causes irreversible chain degradation. Thermolysis in bulk was studied for all compounds by differential scanning calorimetry (DSC). In contrast to the results of the photolysis the alkyl substituent at N3 has an effect on the thermostability of the pentazadiene chromophore.

The photochemical decomposition of substituted 1,5-diaryl-3-alkyl-pentazadiene monomers and polymers induced by UV irradiation with a pulsed excimer laser was monitored by UV-vis spectroscopy. The net photochemical reaction proceeds in an overall one-step pathway AfB. Quantum yields for the laser decomposition are determined to be e10%. An oscillating behavior of the absorption was found during the dark period following the irradiation. The temperature dependence of this dark reaction has been studied. The oscillatory behavior is discussed in the light of current theories concerning instabilities in photochemical systems.

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