Experimental Investigation on Binary Phase Diagram of the Thermotropic Phase Transitions Compounds (n‐CnH2n+1R3)2ZnCl4

The thermotropic phase transitions compounds (n‐C_nH_2n+1R₃)₂ZnCl₄ as well as a series of their binary mixtures were prepared by a solution reflux method from their ethanol solutions. The experimental subsolidus binary phase diagram of n‐C₁₈H₃₇N(CH₃)₃]₂ZnCl₄‐n‐(C₁₈H₃₇)₂N(CH₃)₂]₂ZnCl₄ is constructed over the entire composition range by differential scanning calorimetry(DSC) and X‐ray. Experi‐ mental results indicate one stable intermediate phase n‐C₁₈H₃₇N(CH₃)₃] n‐(C₁₈H₃₇)₂N(CH₃)₂]ZnCl₄ at W_C18C3Zn %=59.75 %, and two invariant three phase equilibria, which shows two eutectoid temperatures: Te₁ at 310±1 K for eutectoid point W_C18C3Zn %=36.24 %, Te₂ at 313±1 K for eutectoid point W_C18C3Zn %=80.17 %. These three noticeable solid‐solution ranges are α‐phase at the left, ?‐phase at the right, and ψ‐phase in the middle of the phase diagram. It is (n‐C_nH_2n+1R₃)₂ZnCl₄ systems as phase change materials that are characterized the phase transition temperatures T in the range of 310 to 340 K, the transition enthalpies ΔH in the range of 38.40 and 168.72 J/g between two polymorphic forms.