Huaxin Gong1,Jan Ilavsky2,Ivan Kuzmenko2,Shucheng Chen1,Hongping Yan1,Christopher Cooper1,Gan Chen1,Yuelang Chen1,Jerika Chiong1,Yuanwen Jiang1,Jiancheng Lai1,Yu Zheng1,Kevin Stone3,Luke Huelsenbeck4,Gaurav Giri4,Jeffrey Tok1,Zhenan Bao1
Stanford University1,Argonne National Laboratory2,SLAC National Accelerator Laboratory3,University of Virginia4
Huaxin Gong1,Jan Ilavsky2,Ivan Kuzmenko2,Shucheng Chen1,Hongping Yan1,Christopher Cooper1,Gan Chen1,Yuelang Chen1,Jerika Chiong1,Yuanwen Jiang1,Jiancheng Lai1,Yu Zheng1,Kevin Stone3,Luke Huelsenbeck4,Gaurav Giri4,Jeffrey Tok1,Zhenan Bao1
Stanford University1,Argonne National Laboratory2,SLAC National Accelerator Laboratory3,University of Virginia4
Flower-like polyacrylonitrile (PAN) particles have shown promising performance for numerous applications, including sensors, catalysis, and energy storage. However, the detailed formation process of these unique structures during polymerization has not been investigated. Here, we elucidate the formation process of flower-like PAN particles through a series of in situ and ex situ experiments such as in situ USAXS. We have the following key findings. First, lamellar petals within the flower-like particles were predominantly orthorhombic PAN crystals. Second, branching of the lamellae during the particle formation arose from PAN’s fast nucleation and growth on pre-existing PAN crystals, which was driven by the poor solubility of PAN in the reaction solvent. Third, the particles were formed to maintain a constant center-to-center distance during the reaction. The separation distance was attributed to strong electrostatic repulsion, which resulted in the final particles’ spherical shape and uniform size. Lastly, we employed the understanding of the formation mechanism to tune the PAN particles’ morphology using several experimental parameters including incorporating comonomers, changing temperature, adding nucleation seeds, and adjusting the monomer concentration. These findings provide important insights into the bottom-up design of advanced nanostructured PAN-based materials and controlled polymer nanostructure self-assemblies.