Uv–vis spectral characteristics of para-aramid fiber deprotonation products in KOH/DMSO system and their applications

This paper reported a spectroscopic method for quantifying the charge content (CT) during para-aramid fiber (PPTA) deprotonation in KOH/DMSO system. The results showed that there were two deprotonation products, i.e., PPTA- and PPTA2- that had spectral absorption at UV/visible wavelength range. It was found that 360 nm was an isosbestic absorption point of PPTA- and PPTA2-, while the absorption at 400 nm was only contributed by PPTA2-. Based on the spectral information, the charge absorption coefficients of PPTA- and PPTA2- at the characteristic wavelengths of interest (i.e., k336PPTA-, k360PPTA- and k400PPTA2-) were calculated, and an equation for quantifying the total charge content was also generated. The present method could provide an efficient quantification tool for monitoring the degree of deprotonation reaction of PPTA in the DMSO/KOH system in the aramid nanofibers related research and application.