混合酰亚胺化方法制备BTDA/ODA型聚酰亚胺薄膜的聚集态结构的研究

Study on the Aggregation Structures of Polyimide Made from BTDA/ODA Through the Mixed Imidization Procedure

采用两步法首先合成聚酰胺酸,然后经热酰亚胺化和混合酰亚胺化工艺制备了BTDA/ODA型的PI-1和PI-2两种聚酰亚胺薄膜。偏光显微镜观察PI-1膜为无定形的,而PI-2膜发现类似"井"型的网状织构,出现了典型的黒十字消光的球晶形貌,球晶直径为0.02～0.03mm,结晶面密度较低,仅为3个/mm2。同时,从PI-2膜的原子力显微镜的相图中观察到,由于链段的有序排列,出现了明暗两个部分,球晶排列形成亮带,无定形部分形成暗带,也构成"井"状,与偏光显微镜观察结果一致,从而证明了有序结构的存在。X-衍射分析表明PI-2膜的有序度高于PI-1膜,另外PI-2膜在2θ=3.115°又出现了一个明显的衍射峰,计算的层间距d=2.83nm,说明经过混合酰亚胺化制备的PI-2膜还生成了一种层状有序结构。其原因在于PI-2体系在经过化学酰亚胺化后形成了部分结构规整的PI链段,起晶核作用,从而导致聚集态有序结构的形成。

PI - 1 and PI - 2 polyimide films were prepared from 3,3′, 4,4′ - benzophenone tetracarboxylic dianhydride （BTDA） and ODA 确良 by two-step polymerization under the thermal and mixed imidization procedures. PLM showed that the PI - 1 film was amorphous and PI - 2 film had a similar ＂well＂ texture and the typical black cross extinction of the morphology of spherulite. The diameter of the spherulite was 0.02 mm to 0.03 mm. At the same time, from the phase diagram of AFM on PI -2 film, as chains in an regular arrangement, there were two parts of bright and shade, which proved that the existence of the a nonrandom structure. From WAXD, the order degree of PI -2 film was higher than that of PI -1 film. SAXD showed that, at 20 = 3. 115°, there was a small diffraction peak from the polyimide film, which is correspondent to a nonrandom samdwich with the layer spacing d = 2.83 nm. The reason was that the PI segmers got from mixed imidization procedure form crystal nucleus which let the molecular chains regularly stack.