Martelo Liliana M, Fonseca Sofia M, Marques Ana T, Burrows Hugh D, Valente Artur J M, Justino Licínia L G, Scherf Ullrich, Pradhan Swapna, Song Qiu
Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal.
Makromolekulare Chemie, Bergische Universität Wuppertal, DE-42097 Wuppertal, Germany.
Polymers (Basel). 2018 Mar 2;10(3):258. doi: 10.3390/polym10030258.
Three anionic fluorene-based alternating conjugated polyelectrolytes (CPEs) have been synthesized that have 9,9-bis(4-phenoxy-butylsulfonate) fluorene-2,7-diyl and 1,4-phenylene (PBS-PFP), 4,4'-biphenylene (PBS-PFP2), or 4,4″--terphenylene (PBS-PFP3) groups, and the effect of the length of the oligophenylene spacer on their aggregation and photophysics has been studied. All form metastable dispersions in water, but can be solubilized using methanol, acetonitrile, or dioxane as cosolvents. This leads to increases in their emission intensities and blue shifts in fluorescence maxima due to break-up of aggregates. In addition, the emission maximum shifts to the blue and the loss of vibronic structure are observed when the number of phenylene rings is increased. Debsity Functional Theory (DFT) calculations suggest that this is due to increasing conformational flexibility as the number of phenylene rings increases. This is supported by increasing amplitude in the fast component in the fluorescence decay. The nonionic surfactant -dodecylpentaoxyethylene glycol ether (CE₅) also breaks up aggregates, as seen by changes in fluorescence intensity and maximum. However, the loss in vibrational structure is less pronounced in this case, possibly due to a more rigid environment in the mixed surfactant-CPE aggregates. Further information on the aggregates formed with CE₅ was obtained by electrical conductivity measurements, which showed an initial increase in specific conductivity upon addition of surfactants, while at higher surfactant/CPE molar ratios a plateau was observed. The specific conductance in the plateau region decreased in the order PBS-PFP3 < PBS-PFP2 < PBS-PFP, in agreement with the change in charge density on the CPE. The reverse process of aggregate formation has been studied by injecting small volumes of solutions of CPEs dissolved at the molecular level in a good solvent system (50% methanol-water) into the poor solvent, water. Aggregation was monitored by changes in both fluorescence and light scattering. The rate of aggregation increases with hydrophobicity and concentration of sodium chloride but is only weakly dependent on temperature.
已合成了三种基于芴的阴离子型交替共轭聚电解质（CPEs），它们含有9,9-双（4-苯氧基丁基磺酸盐）芴-2,7-二亚基和1,4-亚苯基（PBS-PFP）、4,4'-联亚苯基（PBS-PFP2）或4,4″-三联亚苯基（PBS-PFP3）基团，并研究了亚苯基间隔基长度对其聚集和光物理性质的影响。所有这些聚电解质在水中都形成亚稳分散体，但可使用甲醇、乙腈或二氧六环作为共溶剂使其溶解。这导致它们的发射强度增加，并且由于聚集体的分解，荧光最大值发生蓝移。此外，当亚苯基环的数量增加时，观察到发射最大值向蓝光方向移动且振动结构消失。密度泛函理论（DFT）计算表明，这是由于随着亚苯基环数量的增加，构象灵活性增加所致。荧光衰减中快速成分的振幅增加支持了这一点。非离子表面活性剂十二烷基五氧乙烯二醇醚（CE₅）也会使聚集体分解，这可从荧光强度和最大值的变化看出。然而，在这种情况下振动结构的损失不太明显，这可能是由于在混合表面活性剂-CPE聚集体中环境更刚性。通过电导率测量获得了关于与CE₅形成的聚集体的更多信息，测量结果表明，加入表面活性剂后比电导率最初会增加，而在较高的表面活性剂/CPE摩尔比下会观察到一个平稳期。平稳期的比电导率按PBS-PFP3 < PBS-PFP2 < PBS-PFP的顺序降低，这与CPE上电荷密度的变化一致。通过将少量溶解在良溶剂体系（50%甲醇-水）中处于分子水平的CPE溶液注入不良溶剂水来研究聚集体形成的逆过程。通过荧光和光散射的变化监测聚集情况。聚集速率随疏水性和氯化钠浓度的增加而增加，但仅微弱地依赖于温度。
