Quaternary ammonium salts are well-known charge-control agents (CCAs) used widely in electrophotography. Aside from the CCA performance, a high thermal stability is also required because pulverized toners are prepared by kneading CCA with various toner components at 130-180 °C. Therefore, thermal stability has been studied in the present investigation in various quaternary ammonium salts with naphtholsulfonates in terms of structure analysis as well as IR spectra. As a result, the anions are found to play the key role in raising the melting point due to the formation of intermolecular OH…O hydrogen bonds between the OH group of one anion and the sulfonic O atom of the neighboring one. The hydrogen bonds bridge anions either in the form of a onedimensional chain or a dimer.
Kazuya Uta, Yohei Sato, Osamu Yamate, Jin Mizuguchi, "Thermal stability of quaternary ammonium salts used as chargecontrol agents as viewed from their crystal structure" in Proc. IS&T Int'l Conf. on Digital Printing Technologies and Digital Fabrication (NIP24), 2008, pp 34 - 37, https://doi.org/10.2352/ISSN.2169-4451.2008.24.1.art00009_1