**2. Preparation of ammonium group-containing ladder-like PSQs with hexagonally stacked structures**

The author and co-workers have developed a preparation method for ammonium groupcontaining PSQs with controlled molecular and higher-ordered structures by hydrolytic polycondensation (sol–gel reaction) of organotrialkoxysilane monomers containing amino groups in aqueous inorganic acids (Kaneko et al., 2004a; Kaneko et al., 2005a; Kaneko & Iyi, 2007; Kaneko & Iyi, 2010).
