Arrington Clay B, Rau Daniel A, Vandenbrande Johanna A, Hegde Maruti, Williams Christopher B, Long Timothy E
Virginia Tech, Department of Chemistry and Macromolecules Innovation Institute (MII), Blacksburg, Virginia 24061, United States.
Virginia Tech, Department of Mechanical Engineering and Macromolecules Innovation Institute (MII), Blacksburg, Virginia 24061, United States.
ACS Macro Lett. 2021 Apr 20;10(4):412-418. doi: 10.1021/acsmacrolett.1c00032. Epub 2021 Mar 17.
Fully aromatic polyimides are amenable to efficient carbonization in thin two-dimensional (2D) films due to a complement of aromaticity and planarity of backbone repeating units. However, repeating unit rigidity traditionally imposes processing limitations, restricting many fully aromatic polyimides, e.g., pyromellitic dianhydride with 4,4'-oxidianiline (PMDA-ODA) polyimides, to a 2D form factor. Recently, research efforts in our laboratories enabled additive manufacturing of micron-scale resolution PMDA-ODA polyimide objects using vat photopolymerization (VP) and ultraviolet-assisted direct ink write (UV-DIW) following careful thermal postprocessing of the three-dimensional (3D) organogel precursors to 400 °C. Further thermal postprocessing of printed objects to 1000 °C induced pyrolysis of the PMDA-ODA objects to disordered carbon. The pyrolyzed objects retained excellent geometric resolution, and Raman spectroscopy displayed characteristic disordered (D) and graphitic (G) carbon bands. Scanning electron microscopy probed the cross-sectional homogeneity of the carbonized samples, revealing an absence of pore formation during carbonization. Likewise, impedance analysis of carbonized specimens indicated only a moderate decrease in conductivity compared to thin films that were pyrolyzed using an identical carbonization process. Facile pyrolysis of PMDA-ODA objects now enables the production of carbonaceous monoliths with complex and predictable three-dimensional geometries using commercially available starting materials.
由于主链重复单元的芳香性和平面性互补，全芳香族聚酰亚胺适合在二维（2D）薄膜中进行高效碳化。然而，传统上重复单元的刚性会带来加工限制，将许多全芳香族聚酰亚胺，例如均苯四甲酸二酐与4,4'-二氨基二苯醚（PMDA-ODA）聚酰亚胺，限制为二维形态。最近，我们实验室的研究工作通过对三维（3D）有机凝胶前体进行仔细的400℃热后处理，实现了使用光固化（VP）和紫外辅助直接墨水书写（UV-DIW）对微米级分辨率的PMDA-ODA聚酰亚胺物体进行增材制造。将打印物体进一步热后处理至1000℃会使PMDA-ODA物体热解为无序碳。热解后的物体保留了出色的几何分辨率，拉曼光谱显示出特征性的无序（D）和石墨（G）碳带。扫描电子显微镜探测了碳化样品的横截面均匀性，发现在碳化过程中没有形成孔隙。同样，碳化样品的阻抗分析表明，与使用相同碳化工艺热解的薄膜相比，其电导率仅适度下降。PMDA-ODA物体的简易热解现在能够使用市售起始材料生产具有复杂且可预测三维几何形状的碳质整体材料。
