Wu Mingyan, Kaur Palwinder, Yue Hongjun, Clemmens A M, Waldeck David H, Xue Cuihua, Liu Haiying
Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
J Phys Chem B. 2008 Mar 20;112(11):3300-10. doi: 10.1021/jp7099527. Epub 2008 Feb 29.
This work shows that low charge density poly(p-phenylene-ethynylene)s (PPE-SO3Na-L and PPE-CO2Na-L), which feature sulfonate and carboxylate groups on every other phenyl ring, form aggregates in water, whereas high charge density poly(p-phenylene-ethynylene)s (PPE-SO3Na-H and PPE-CO2Na-H), which possess sulfonate or carboxylate groups on every phenyl ring, do not aggregate in water. The formation of aggregates of PPE-SO3Na-L and PPE-CO2Na-L is demonstrated by comparing the concentration and temperature dependence of their steady-state spectra in water to that in DMSO, in which the two polymers do not aggregate. For the weak polyelectrolytes PPE-CO2Na-H and PPE-CO2Na-L, the solution pH was changed to vary the charge density. In addition, the cationic surfactant, octadecyltrimethyl ammonium, is shown to dissociate the low charge density polymer aggregates and to form supramolecular complexes with each of the different polyelectrolytes. Fluorescence correlation spectroscopy was applied to provide insight into the sizes of aggregates under different solution conditions.
这项工作表明，每隔一个苯环带有磺酸根和羧酸根的低电荷密度聚对苯撑乙炔（PPE-SO3Na-L和PPE-CO2Na-L）在水中形成聚集体，而每个苯环都带有磺酸根或羧酸根的高电荷密度聚对苯撑乙炔（PPE-SO3Na-H和PPE-CO2Na-H）在水中不聚集。通过比较PPE-SO3Na-L和PPE-CO2Na-L在水中与在二甲基亚砜（DMSO）中的稳态光谱的浓度和温度依赖性，证明了它们聚集体的形成，这两种聚合物在二甲基亚砜中不聚集。对于弱聚电解质PPE-CO2Na-H和PPE-CO2Na-L，通过改变溶液pH来改变电荷密度。此外，阳离子表面活性剂十八烷基三甲基铵能使低电荷密度聚合物聚集体解离，并与每种不同的聚电解质形成超分子复合物。应用荧光相关光谱来深入了解不同溶液条件下聚集体的大小。
