β-Resin was extracted by solvent separation of refined coal tar pitch. Several analytical methods revealed that β-resin had a better aromatic plane packing structure and a higher number of carbon residues, making it ideal for mesophase transformation. The mesophase transformation process of β-resin (the formation of liquid-crystalline spheres, the growth of mesophase spheres, and the coalescence and disintegration of mesophase spheres) was observed in situ using a polarizing microscope with a hot stage. Moreover, the mesophase transformation mechanism of β-resin was investigated at each transformation stage. The mesophase content and mesophase transformation kinetics were analyzed based on the area method and quinoline insoluble (QI) substitution method. Both methods revealed changes in the mesophase content of β-resin. However, the test results of the two methods were slightly different at the initial stage of mesophase transformation and tended to be consistent during the later stage.

In situ observation of mesophase transformation behaviour and mechanistic analysis in β-resin
    Abstract
    1 Introduction
    2 Experimental section
        2.1 Raw materials
        2.2 Extraction of β-resin
        2.3 Sample characterization
        2.4 Mesophase transformation process
    3 Results and discussion
        3.1 Composition and structure
            3.1.1 Solid-state 13C-NMR analysis
        3.2 FTIR analysis
        3.3 Molecular mass distribution by MALDI-TOF
        3.4 TG and DTG analysis
    4 In situ optical microscopy and mechanism of mesophase transformation analysis of β-resin
        4.1 XRD analysis of β-resin before and after mesophase transformation
        4.2 Mesophase transformation kinetics of β-resin
    5 Conclusion
    Acknowledgements 
    References

• Ben Liu(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China, Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China) Corresponding author
• Xi Yan(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China)
• Zechao Tao(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China)
• Xiangfen Li(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China)
• Shiwen Lei(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China)
• Dongqing Zhang(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China)
• Zonghe Yang(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China, Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China)
• Zhanjun Liu(Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, China, Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China)