Prepartion And Property Investigations Of Order-DIS Order Molecular Phase Change Crystal Materials

The order-disorder structure unit is usually utilized to effectively build excellent phase change material, which has been comfirmed by the the micro-mechanism of phase transition. The molecule configuration transition triggered by the change of ambient temperature will result in the structure phase change of the compound. Two kinds of order-disorder structure unit-N-benzylisopropylamine(N-BPA) and triethylene diamine (DABCO) have been introduced to assemble five phase change compounds, N-BPA+·BF4-(1), N-BPA+·C104-(2), N-BPA+·HCCl2COO-(3), N-BPA+-HCF2COO-(4) and the co-crystal compound DABCOTU (TU=thiourea)(5). The structures, thermal and dielectric properties of the compounds have been investigated. The phase transitions of compounds1and2occur at-71℃and-74℃respectively, due to the order-disorder movement of methyl in N-benzylisopropylamine, which leads to the change of space group from high temperature phase C2/m to low temperature phase C2/c. The space group of compound3is P21/c at room temperature, and the structure phase transformation occurs at96℃Ferroelectric phase transition at-35℃in compound4has been studied. The low temperature paraelectric phase and high temperature ferroelectric phase space group are P21/n and Pc respectively, mainly due to the order-disorder movement of fluorine atoms of difluoroacetic acid. The tructural phase transition of compound5occurs at-89℃with the uniform space group C2/c. The order-disorder motion and the N-H…N hydrogen bond between DABCO and thiourea are probably the main factors of the phase transition in5.