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Increasing the Content of β Phase of Poly(9,9-dioctylfluorene) by Synergistically Controlling Solution Aggregation and Extending Film-forming Time

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Abstract

For poly(9,9-dioctylfuorene) (PFO), β phase (coplanar conformation with the intra-chain torsion angle of 165°) has a greater conjugation length and higher degree of order compared to those of α phase, which favors charge carrier transport. However, the highest content of β phase obtained so far is 45%. We propose to increase the content of β phase by promoting the solution aggregation of PFO molecules and extending film-forming time. For this purpose, 1,8-diiodooctane (DIO) is added to PFO o-xylene solution, which enhances the interaction of PFO chains and improves the planarity of PFO backbone, resulting in the formation of ordered aggregation. The aggregates act as nucleation centers to promote the formation of β phase. The content of β phase increases with increasing DIO concentration and reaches a platform of 39% as DIO is more than 4 vol%. Furthermore, the film is kept in a sealed environment with o-xylene atmosphere for 3 h, thus the PFO molecules have enough time to diffuse to the crystallization front and achieve disorder-order transition. As a result, the crystallinity of PFO is improved significantly and the content of β phase increases to 52%, reaching the highest value reported so far.

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Nos. 51890871, 91833306, and 51573185), and the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB12020300).

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  1. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, China

    Ya-Di Liu, Qiang Zhang, Xin-Hong Yu, Jian-Gang Liu & Yan-Chun Han

  2. University of Science and Technology of China, Hefei, 230026, China

    Ya-Di Liu

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Liu, YD., Zhang, Q., Yu, XH. et al. Increasing the Content of β Phase of Poly(9,9-dioctylfluorene) by Synergistically Controlling Solution Aggregation and Extending Film-forming Time. Chin J Polym Sci 37, 664–673 (2019). https://doi.org/10.1007/s10118-019-2259-3

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