Hydrogen-Bonded Network in Quaternary Ammonium Salts Used as Charge Control Agents

We have previously investigated the origin of the unusual high thermal stability of benzyltributylammonium-4-hydroxynaphthalene-1-sulfonate used as a charge control agent (P-51 : Orient Chemical Industries, Ltd.) from the standpoint of the X-ray structure analysis. In anions of P-51, we found chains of OH…O intermolecular hydrogen-bonds between the OH group of one anion and the sulfonate O atom of the neighboring one. The present hydrogen-bond network is found to impart a polymer-like stability to P-51. In the present investigation, we extended our studies to seven derivatives of P-51, in which the cation remains the same while the anion part is modified. Among these, five derivatives are solid and possess various OH…O hydrogen-bond networks in anions : dimer, or one-dimensional, or two-dimensional network. These results lead us to conclude that the hydrogen-bond network is responsible for the high thermal stability of P-51 derivatives. On the other hand, the remaining two derivatives are found to be liquid at room temperature, probably because of the lack of intermolecular hydrogen bonds