Dependence of Piezoelectric and Pyroelectric Activities of Aromatic Polyurea Thin Films on Monomer Composition Ratio
Dependence of Piezoelectric and Pyroelectric Activities of Aromatic Polyurea Thin Films on Monomer Composition Ratio
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芳香族聚脲薄膜的压电和热释电活性对单体组成比的依赖性
DOI：
10.1143/jjap.32.2768
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发表时间：
1993
影响因子：
1.5
通讯作者：
Eiichi Fukada Eiichi Fukada
中科院分区：
文献类型：
--
作者：
Xian–Shan Wang;M. Iijima;Yoshikazu Takahashi Yoshikazu Takahashi;Eiichi Fukada Eiichi Fukada
采用4，4 ′-二氨基二苯甲烷（MDA）和4，4 ′-二苯甲烷二异氰酸酯（MDI）同时沉积法在聚酰亚胺薄膜上制备了芳香族聚脲薄膜。通过改变单体的蒸发温度，改变沉积膜的MDA与MDI的单体摩尔比以产生富含MDA的、平衡的和富含MDI的膜。极化后，平衡膜的热释电和压电常数达到最大值，在200°C下仍保持稳定。元素分析证实，低聚物组成的约五个单体存在于沉积膜。在平衡膜中，在DSC测量的第一轮中在约110°C处出现放热峰，并且在热处理后由于异氰酸酯基团而导致的IR吸收峰消失。这些结果表明，在极化过程中，形成极性脲键的低聚物的聚合在约110°C下在高电场下发生。由此产生的大的剩余极化导致高的热释电和压电活性。
Thin films of aromatic polyurea were prepared by simultaneous deposition of 4,4'-diamino diphenylmethane (MDA) and 4,4'-diphenylmethane diisocyanate (MDI) on a polyimide film substrate. By changing the evaporation temperature of the monomers, the monomer molar ratio of MDA to MDI of the deposited film was varied to yield MDA-rich, balanced, and MDI-rich films. After poling, the balanced films exhibited the maximum values of pyroelectric and piezoelectric constants, which were stable up to 200°C. Elemental analysis confirmed that oligomers consisting of about five monomers were present in as-deposited films. In the balanced films, an exothermic peak appeared at about 110°C in the first run of DSC measurements and the IR absorption peak due to isocyanate groups disappeared after heat treatment. These results suggest that during the poling process polymerization of oligomers, which forms polar urea bonds, takes place at about 110°C under a high electric field. The large residual polarization thus produced leads to high pyroelectric and piezoelectric activities.