Synthesis and characterisation of new hard polyurethanes with triazene pendants

Three new hard type polyurethanes based on 2,4-toluene diisocyanate (2,4-TDI) and different triazene diols, namely 1-phenyl-3,3′-di(2-hydroxyethyl) triazene (PT-D), 1-naphthyl-3,3′-di(2-hydroxyethyl) triazene (NT-D) and 1-(4-nitro)-phenyl-3,3′-di(2-hydroxyethyl) triazene (NOT-D) were synthesized and characterized. The photosensitivity of these polymers was evaluated by UV irradiation, in DMF solution and as films by following the disappearance of the π–π* absorption band corresponding to the triazene group. The polyurethane containing the NOT-D monomer revealed no decrease of its absorption bands even during prolonged irradiation, but could be structured with high quality using 308 nm laser irradiation. The ablation results revealed that the etching depth could be controlled by varying the laser fluence and number of laser pulses.