Robust chain aggregation of low-entropy rigid ladder polymers in solution
Robust chain aggregation of low-entropy rigid ladder polymers in solution
复制标题
溶液中低熵刚性梯形聚合物的稳健链聚集
DOI：
10.1039/d2tc00761d
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发表时间：
2022
影响因子：
6.4
通讯作者：
Gu, Xiaodan
中科院分区：
文献类型：
--
作者：
Ma, Guorong;Leng, Mingwan;Li, Shi;Cao, Zhiqiang;Cao, Yirui;Tabor, Daniel P.;Fang, Lei;Gu, Xiaodan
共轭聚合物已被广泛研究，其中梯型共轭聚合物由于其刚性主链和非凡的性能而受到更多关注。然而，对梯形聚合物的刚性构象如何转化为材料特性的理解仍然有限。在这里，我们通过光散射、中子散射和紫外可见吸收光谱表征技术系统地研究了咔唑衍生的共轭梯形聚合物（LP）及其类似的非梯形控制聚合物（CP）的溶液聚集特性，揭示了LP的高度鲁棒性、温度不敏感的聚集行为。通过计算分子动力学模拟进一步验证了实验结果。我们发现，在氯苯溶液中，LP 的紫外光谱的峰值位置和强度在 20 °C 至 120 °C 之间保持恒定。通过在氯苯溶液中从 20 °C 到 70 °C 的动态光散射测量，该聚合物还表现出稳定的流体动力学半径。使用小角度中子散射，即使在高温下，在测量的 q 范围低至 0.008 Å−1 时也没有达到吉尼尔区。相反，非梯形控制聚合物CP完全溶解在氯苯溶剂中，没有观察到任何明显的聚集体。布朗动力学模拟表明，在聚合物聚集过程中，LP 的熵变负值明显小于非梯形控制聚合物。这些发现揭示了刚性共轭梯形聚合物的低熵性质及其聚集的低熵损失，这有望在高温下实现高度鲁棒的分子间相互作用。刚性梯形聚合物的这种独特的热力学特征可用于在非常规高温条件下工作的下一代电子和光电器件的设计和应用。
Conjugated polymers have been widely investigated where ladder-type conjugated polymers receive more attention due to their rigid backbones and extraordinary properties. However, the understanding of how the rigid conformation of ladder polymers translates to material properties is still limited. Here, we systematically investigated the solution aggregation properties of a carbazole-derived conjugated ladder polymer (LP) and its analogous non-ladder control polymer (CP) via light scattering, neutron scattering, and UV-vis absorption spectroscopy characterization techniques, revealing a highly robust, temperature-insensitive aggregation behavior of the LP. The experimental findings were further validated by computational molecular dynamics simulations. We found that the peak positions and intensities of the UV spectra of the LP remained constant between 20 °C and 120 °C in chlorobenzene solution. The polymer also showed a stable hydrodynamic radius measured by dynamic light scattering from 20 °C to 70 °C in the chlorobenzene solution. Using small-angle neutron scattering, no Guinier region was reached in the measured q range down to 0.008 Å−1, even at elevated temperature. In contrast, the non-ladder control polymer CP was fully soluble in the chlorobenzene solvent without the observation of any notable aggregates. The Brownian dynamics simulation showed that during polymer aggregation, the entropy change of the LP was significantly less negative than that of the non-ladder control polymer. These findings revealed the low entropy nature of rigid conjugated ladder polymers and the low entropy penalty for their aggregation, which is promising for highly robust intermolecular interactions at high temperatures. Such a unique thermodynamic feature of rigid ladder polymers can be leveraged in the design and application of next-generation electronic and optoelectronic devices that function under unconventional high temperature conditions.