Clark Andrew P-Z, Cadby Ashley J, Shen Clifton Kwang-Fu, Rubin Yves, Tolbert Sarah H
Department of Chemistry & Biochemistry, University of California Los Angeles, Los Angeles, California 90095-1569, USA.
J Phys Chem B. 2006 Nov 9;110(44):22088-96. doi: 10.1021/jp060070d.
We have synthesized a conjugated amphiphilic polyelectrolyte, a poly(phenylene ethynylene) (PPE), and the structurally analogous neutral polymer. The solution-phase aggregation of the uncharged PPE can be reversibly controlled by varying the solvent polarity and concentration, while the charged polymer appears to self-assemble at any concentration in compatible solvents. These conclusions are based on a combination of absorption and photoluminescence spectroscopy and dynamic light scattering. Photoinduced absorption spectroscopy was also employed to investigate interchain electronic communication and the photoinduced production of free charge carriers. The uncharged PPE had a relatively high polaron yield, indicating pi-stacking of adjacent PPE chains and efficient exciton splitting, while the charged polymer did not produce polarons, indicating that the polymers are not pi-stacked despite their tendency to form aggregates. This is most likely due to the presence of the cationic trimethylammonium side chains which force neighboring polymer chains too far apart to achieve effective pi-orbital overlap. Polarons were observed in both polymers after chemical doping with iodine. The ability to control aggregation and interchain electronic communication could be a useful tool in designing nanostructured electronic materials.
我们合成了一种共轭两亲性聚电解质、一种聚亚苯基乙炔（PPE）以及结构类似的中性聚合物。通过改变溶剂极性和浓度，可以可逆地控制不带电荷的PPE在溶液相中的聚集，而带电荷的聚合物在相容溶剂中的任何浓度下似乎都会自组装。这些结论是基于吸收光谱、光致发光光谱以及动态光散射的综合结果。还采用光致吸收光谱来研究链间电子通信以及光致自由电荷载流子的产生。不带电荷的PPE具有相对较高的极化子产率，表明相邻PPE链存在π堆积且激子有效分裂，而带电荷的聚合物不产生极化子，这表明尽管聚合物有形成聚集体的倾向，但它们并未发生π堆积。这很可能是由于阳离子三甲基铵侧链的存在，使得相邻聚合物链间距过大而无法实现有效的π轨道重叠。在用碘进行化学掺杂后，两种聚合物中均观察到了极化子。控制聚集和链间电子通信的能力可能是设计纳米结构电子材料的有用工具。
