Thermal behaviour of mixed long-chain alkylammonium tetrachlorozincates

Mixed crystals of composition (n-C_mH_2m+1NH₃)_2xm(n-C_nH_2n+1 · NH₃)_2?2xm ZnCl₄ (m= 12; n=14, 16, 18) are formed upon annealing mechanical mixtures of layer compounds (n-C_nH_2n+1NH₃)₂ZnCl₄, through solid state diffusion of the n-alkylammonium cations. From a common high temperature monophasic modification, in which the polymethylenic chains are conformationally molten, different modifications are obtained on cooling [depending on the (n ? m) value] in which chain crystallinity is developed. The structure of such modifications is speculated on the grounds of DSC and preliminary X-ray diffractometric and IR data, and compared with that of similar previously characterized systems.