含苯并咪唑低热胀聚酰亚胺的合成及性能

Synthesis and Properties of Low Thermal Expansion Polyimide Containing Benzimidazole Group

以2-(4-氨基苯基)-5-氨基苯并咪唑(PABZ)、对苯二胺(PDA)、3,3’,4,4’-联苯四羧酸二酐(BPDA)为原料成功制备了一系列含苯并咪唑的高耐热低热胀聚酰亚胺(PI),并表征了其结构和性能。红外吸收光谱表明聚合物已经亚胺化;X射线衍射表明PABZ的摩尔分数超过5%的聚酰亚胺分子链之间的距离更窄,含20%PABZ的聚合物d间距仅为0.425nm;热重分析表明随着PABZ的加入,1%的失重温度从565℃降低到532℃;热机械分析表明材料线膨胀系数呈先增大再减小的趋势,随着分子链中苯并咪唑含量的增加,线膨胀系数从10.2×10^(-6)K^(-1)下降到2.7×10^(-6)K^(-1)。通过分子模拟表明:苯并咪唑中的—NH—可以与酰亚胺环的C=O产生氢键,导致分子链之间的间距更小,自由体积分数更小,相互之间作用力更大,拥有更低的线膨胀系数。力学性能测试表明,苯并咪唑的引入,薄膜的拉伸强度和模量小幅上升,断裂伸长率稍微下降。

Low thermal expansion polyimide film was prepared by incorporating 2-(4-Aminophenyl)-1H-benzimidazol-5-amine(PABZ)into polymer backbones 3,3′,4,4′-biphenyltetracarboxylic dianhydride(BPDA)/p-phenylenediamine(PDA)and the structure as well as properties was characterized.Fourier transform infrared spectroscopy(FTIR)indicates fully imidization of the materials.Wide angle X-ray diffraction(WAXD)shows that the d-spacing of PI chain becomes narrower when the content of PABZ,exceeds 5%.And the d-spacing of the polymer with 20%PABZ remains only 0.425 nm.With the increasing addition of PABZ,the 1%weight loss temperature decreases from 565 to 532 ℃.The mechanical thermal analysis indicates that the linear expansion coefficient of the film decreases from 10.2×10~(-6) to 2.7×10~(-6) K~(-1).Molecular simulations show that hydrogen bond would emerge between —NH— in PABZ and C=O in imide ring,resulting in smaller spacing between molecular chains,smaller free volume fraction,greater interaction forces,and lower thermal expansion coefficients.The mechanical property tests prove that both the tensile strength and modulus of the film increase and the elongation at break decreases slightly with the introduction of PABZ.