Simple Molecular Ferroelectrics: N,N′-Dialkylterephthalamide Derivatives in the Solid Phase
Simple Molecular Ferroelectrics: N,N′-Dialkylterephthalamide Derivatives in the Solid Phase
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简单分子铁电体：固相 N,N-二烷基对苯二甲酰胺衍生物
DOI：
10.1039/d1tc05001j
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发表时间：
2022
影响因子：
6.4
通讯作者：
Tomoyuki Akutagawa
中科院分区：
文献类型：
--
作者：
Moeko Kawana;Ryohei Mizoue Ryohei;Takashi Takeda;Norihisa Hoshino;Tomoyuki Akutagawa
简单的N，N′-二烷基-1，4-苯二甲酰胺（CnIPA）分子形成一维（1D）N-H-O氢键分子组装体，该组装体在相变为各向同性液体之前通过烷基链的部分熔融表现出固-固相变，但没有形成液晶相.通过改变-CONHCnH 2n +1的烷基链长度（n）（n = 5-16，18）来评估CnTPA的相变、分子组装结构、介电常数和铁电性。一维氢键结构进一步组装成双层排列的烷基链，形成层状型分子组装体，其中两个烷基链的部分熔融发生在高温固相。在CnTPA的相变行为和T依赖的介电常数中观察到奇偶效应，其中偶数导数比奇数导数具有更大的运动自由度。介电响应与极性结构单元N-H-O氢键的运动自由度相关，其动力学在相变到高T固相后的T范围内被激活。在n ≥ 11的CnTPAs的铁电极化-电场（P-E）曲线中观察到N-H-O氢键链的集体偶极反转。高温固相中长烷基链的熔融状态有助于N-H-O单元的偶极反转，形成氢键铁电体。
Simple molecules of N,N′-dialkyl-1,4-benzenedicarboxamide (CnIPA) form a one-dimensional (1D) N–H⋯O hydrogen-bonding molecular assembly, which shows a solid–solid phase transition through the partial melting of alkyl chains before phase transition to an isotropic liquid without the formation of a liquid crystal phase. The phase transition, molecular assembly structure, dielectric constant, and ferroelectricity of CnTPA were evaluated by changing the alkyl chain length (n) of –CONHCnH2n+1 through n = 5–16, 18. The 1D hydrogen-bonded structures were further assembled into a bilayer arrangement of alkyl chains to form a lamellar-type molecular assembly, where the partial melting of two alkyl chains occurred at the high-T solid phase. An even–odd effect was observed in the phase transition behavior and the T-dependent dielectric constants of CnTPA, where the even-number derivatives had much larger motional freedom than those of the odd-number derivatives. The dielectric response was associated with the motional freedom of the polar structural unit of N–H⋯O hydrogen bonds, the dynamics of which were activated in the T range after the phase transition to the high-T solid phase. The collective dipole inversion of the N–H⋯O hydrogen-bonding chain was observed in the ferroelectric polarization–electric field (P–E) hysteresis curves of CnTPAs with n ≥ 11. The melting state of long alkyl chains in the high-T solid phase assisted the dipole inversion of N–H⋯O units to form hydrogen-bonded ferroelectrics.