Ma Guorong, Li Zhaofan, Fang Lei, Xia Wenjie, Gu Xiaodan
School of Polymer Science and Engineering, The University of Southern Mississippi, Hattiesburg, MS, 39406, USA.
Department of Aerospace Engineering, Iowa State University, Ames, IA 50011, USA.
Nanoscale. 2024 Mar 28;16(13):6495-6506. doi: 10.1039/d3nr05721f.
Conjugated polymers (CPs) are solution-processible for various electronic applications, where solution aggregation and dynamics could impact the morphology in the solid state. Various solvents and solvent mixtures have been used to dissolve and process CPs, but few studies have quantified the effect of solvent quality on the solution behavior of CPs. Herein, we performed static light scattering and small-angle X-ray scattering combined with molecular dynamics (MD) simulation to investigate CP solution behaviors with solvents of varying quality, including poly(3-alkylthiophene) (P3ATs) with various sidechain lengths from -CH to -CH, poly[bis(3-dodecyl-2-thienyl)-2,2'-dithiophene-5,5'-diyl] (PQT-12) and poly[2,5-bis(3-dodecylthiophen-2-yl)thieno[3,2-]thiophene] (PBTTT-12). We found that chlorobenzene is a better solvent than toluene for various CPs, which was evident from the positive second virial coefficient ranging from 0.3 to 4.7 × 10 cm mol g towards P3ATs. For P3ATs in non-polar solvents, longer sidechains promote more positive , indicating a better polymer-solvent interaction, wherein for toluene increases from -5.9 to 1.4 × 10 cm mol g, and in CB, ranges from 1.0 to 4.7 × 10 cm mol g when sidechain length increases from -CH to -CH. Moreover, PQT-12 and PBTTT-12 have strong aggregation tendencies in all solutions, with an apparent positive (∼0.5 × 10 cm mol g) due to multi-chain aggregates and peculiar chain folding. These solvent-dependent aggregation behaviors can be well correlated to spectroscopy measurement results. Our coarse-grained MD simulation results further suggested that CPs with long, dense, and branched sidechains can achieve enhanced polymer-solvent interaction, and thus enable overall better solution dispersion. This work provides quantitative insights into the solution behavior of conjugated polymers that can guide both the design and process of CPs toward next-generation organic electronics.
共轭聚合物（CPs）可通过溶液加工用于各种电子应用，其中溶液聚集和动力学可能会影响固态形态。各种溶剂和溶剂混合物已被用于溶解和加工CPs，但很少有研究量化溶剂质量对CPs溶液行为的影响。在此，我们进行了静态光散射和小角X射线散射，并结合分子动力学（MD）模拟，以研究CPs在不同质量溶剂中的溶液行为，包括侧链长度从-CH到-CH的各种聚（3-烷基噻吩）（P3ATs）、聚[双（3-十二烷基-2-噻吩基）-2,2'-二噻吩并-5,5'-二基]（PQT-12）和聚[2,5-双（3-十二烷基噻吩-2-基）噻吩并[3,2-]噻吩]（PBTTT-12）。我们发现，对于各种CPs来说，氯苯是比甲苯更好的溶剂，这从对P3ATs的第二维里系数为正（范围从0.3到4.7×10 cm³mol⁻¹g⁻²）可以明显看出。对于非极性溶剂中的P3ATs，较长的侧链会促进更正的第二维里系数，表明聚合物-溶剂相互作用更好，其中对于甲苯，第二维里系数从-5.9增加到1.4×10 cm³mol⁻¹g⁻²，而在氯苯中，当侧链长度从-CH增加到-CH时，第二维里系数范围从1.0到4.7×10 cm³mol⁻¹g⁻²。此外，PQT-12和PBTTT-12在所有溶液中都有很强的聚集倾向，由于多链聚集体和特殊的链折叠，其第二维里系数明显为正（约0.5×10 cm³mol⁻¹g⁻²）。这些依赖于溶剂的聚集行为与光谱测量结果有很好的相关性。我们的粗粒化MD模拟结果进一步表明，具有长、密和分支侧链的CPs可以实现增强的聚合物-溶剂相互作用，从而使整体溶液分散性更好。这项工作为共轭聚合物的溶液行为提供了定量见解，可指导CPs用于下一代有机电子器件的设计和加工。
