Antunes Filipe E, Lindman Björn, Miguel Maria G
Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.
Langmuir. 2005 Oct 25;21(22):10188-96. doi: 10.1021/la050590k.
Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification, and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separately can give high viscosities and a gel-like behavior, a pronounced maximum in viscosity and storage modulus with the mixing ratio of the polyelectrolytes is observed; the maximum is located between the points of charge and hydrophobe stoichiometry and reflects a combination of hydrophobic and electrostatic association. Lowering the charge density of the anionic polymer leads to a strengthened association at first, but at lower charge densities there is a weakened association due to the onset of phase separation. The strength of the electrostatic interaction was modified by adding salt. Increased ionic strength can lead to phase separation and to increased or decreased viscosity depending on the polyelectrolyte mixing ratio.
对两种带相反电荷的疏水改性聚电解质的水性混合物进行了流变学和相分离研究。通常在带相反电荷的聚合物混合物中出现的典型相分离，由于疏水改性的存在而显著减少，并且仅在接近电荷中和点时才检测到相分离。虽然两种聚电解质单独使用时可产生高粘度和类似凝胶的行为，但观察到随着聚电解质混合比例的变化，粘度和储能模量出现明显的最大值；该最大值位于电荷与疏水基团化学计量点之间，反映了疏水和静电缔合的组合。降低阴离子聚合物的电荷密度首先会导致缔合增强，但在较低电荷密度下，由于相分离的开始，缔合会减弱。通过添加盐来改变静电相互作用的强度。增加离子强度可导致相分离，并根据聚电解质混合比例使粘度增加或降低。
