Polyfluorene (PF) Single-Chain Conformation, β Conformation, and Its Stability and Chain Aggregation by Side-Chain Length Change in the Solution Dynamic Process
Polyfluorene (PF) Single-Chain Conformation, β Conformation, and Its Stability and Chain Aggregation by Side-Chain Length Change in the Solution Dynamic Process
复制标题
溶液动态过程中侧链长度变化的聚芴 (PF) 单链构象、β构象及其稳定性和链聚集
DOI：
10.1021/acs.jpcc.8b03504
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发表时间：
2018-07-05
影响因子：
3.7
通讯作者：
Lu, Dan
中科院分区：
文献类型：
--
作者：
Liu, Bin;Li, Tao;Lu, Dan
采用动态/静态光散射、紫外-可见吸收光谱等方法，系统研究了不同碳原子序数的烷基侧链长度对聚（9,9-二己基芴）（PF6）、聚（9,9-二庚基芴）（PF7）、聚（9,9-二辛基芴）（PF8）、聚（9,9-二壬基芴）（PF9） （PF10）聚芴单链构象、β构象的影响，以及聚（9,9-二癸基芴）在溶液动力学过程中的稳定性和链聚集性。光致发光光谱和扫描电子显微镜。β构象为低能链构象，PF8、PF9和PF10的紫外可见光谱特征峰分别在437、427和428 nm处。有趣的是，随着侧链长度的增加，PF单链在甲苯溶液中的形状参数（R-g/R-h）（即旋转半径（R-g）与流体动力半径（R-h）之比）呈现奇偶性，这表明偶数碳原子的PF单链比奇数碳原子的PF单链刚性更强。在PF8、PF9和PF10的甲苯/乙醇混合溶液中，β构象的含量最高，均为42%，但PF8最易形成β构象，PF9次之，PF10最后。首次发现β -构象的形成和含量与链的堆积密度密切相关，而与聚集大小无关。高链堆积密度更有利于β -构象的形成；静态分形维数（d(f)）很好地证明了这一点，它反映了链聚集的紧密性（即链的堆积密度）和链的自相似度，并从SLS中用指数律计算。此外，我们还发现，在高乙醇含量（80%）条件下，即使放置21 d， β -构象含量也可以稳定在最大值范围（42%），且与侧链长度无关，而在低乙醇含量（30%和40%）条件下，β -构象含量也可以稳定在两个不同的时间阶段。这些结论对于深入理解基于凝聚态物理的共轭聚合物成膜的溶液动力学过程，控制其凝聚态结构，实现具有高载流子迁移率、稳定性和效率的光电器件具有重要意义。
The effects of alkyl side-chain length with different carbon atom number, called poly(9,9-=di-hexlyfluorene) (PF6), poly(9,9-diheptylfluorene) (PF7), poly(9,9-dioctylfluorene) (PF8), poly(9,9-dinonylfluorene) (PF9), and poly(9,9-didecylfluorene) (PF10), on the polyfluorene (PF) single-chain conformation, beta conformation, and its stability and chain aggregation in the solution dynamic process were systematically investigated by dynamic/static light scattering, UV-vis absorption spectra, photoluminescence spectra, and scanning electron microscopy. beta conformation was the low energy chain conformation, and its characteristic peak was at 437, 427, and 428 nm in the UV vis spectrum of PF8, PF9, and PF10, respectively. It was interestingly found that the shape parameters (R-g/R-h) (i.e., ratio of radius of gyration (R-g) and hydrodynamic radius (R-h)) of PF single chains in toluene solution showed an odd even property with the increase in side-chain length, which revealed that PF chains with even carbon atoms were more rigid than those with odd carbon atoms. The highest contents of beta conformation were all similar to 42% in PF8, PF9, and PF10 toluene/ethanol mixed solutions, but PF8 most easily formed the beta conformation, PF9 followed, and PF10 was last. It was first found that the beta-conformation formation and content were strongly connected to the chain packing density but not to aggregation size. High chain packing density was more advantageous to beta-conformation formation; it had been well proved by static fractal dimension (d(f)), reflecting the compactness of chain aggregation (i.e., chain packing density) and the chain self-similarity, and calculated by exponential law from SLS. Besides, it was also found that the beta-conformation content could be stabilized at the maximum value range (42%) in the high ethanol content (80%) and independent of the side-chain length even after placing for 21 days, whereas in lower ethanol content (30 and 40%), the beta-conformation content could also be stabilized in two different time stages. The conclusions are significant to understand deeply the solution dynamics process of film formation based on condensed matter physics of the conjugated polymer to control its condensed matter structure to achieve photoelectric devices with high carrier mobility, stability, and efficiency.