Synthesis and photochemical investigations of novel bistriazene polyurethanes

Two bistriazene monomers, 1,1′[4,4′-diphenyl]-3,3′-di(β-hydroxyethyl, methyl)-bistriazene (T1) and 1,1′[4,4′-diphenylsulfone]-3,3′-di(β-hydroxyethyl, methyl)-bistriazene (T2) were prepared by an electrophilic N–N coupling of substituted aryldiazonium salts with N-methyl-aminoethanol, and further employed as reaction partners for 2,4-toluene diisocyanate (2,4- and 2,6-TDI isomer mixture, 80:20, v/v) or 4,4′ methylene bis(phenylisocyanate) to achieve hard type bistriazene polyurethanes. The synthesized monomers and polymers were characterized by analytical and spectroscopic methods, while the surface morphology of polymers was visualized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Photochemical assessment of the triazene moieties in monomers and polymers was carried out in solution (methanol, DMF) and film state, following the decreasing under UV irradiation of the π–π* absorption band in the corresponding UV spectra, the kinetic evaluation indicating a first order photoprocess. Laser ablation experiments performed at an irradiation wavelength of λ = 308 nm illustrate that bistriazene polyurethanes have a high potential to furnish good quality surfaces intended for microlithography.