Ultraviscosity in Entangled Polyelectrolyte Complexes and Coacervates
Ultraviscosity in Entangled Polyelectrolyte Complexes and Coacervates
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DOI：
10.1021/acs.macromol.0c00133
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发表时间：
2020-06-09
期刊：
影响因子：
5.5
通讯作者：
Schlenoff, Joseph B.
中科院分区：
文献类型：
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作者：
Akkaoui, Khalil;Yang, Mo;Schlenoff, Joseph B.
带相反电荷的聚电解质的自发缔合是液-液相分离的一个例子。所得的水合的水化的水化复合物或凝聚物（两者均称为“佩奇”）显示出宽范围的粘度。除了凝聚中性聚合物预期的粘度对分子量和体积分数的通常依赖性之外，佩奇还含有正Pol（+）和负Pol（-）重复单元之间的密集电荷配对。这些“贴纸”在多个长度尺度上减慢聚合物链动力学。Pol（+）Pol（-）电荷对可以通过向接触佩奇的溶液中加入盐来破坏，从而降低粘度（“saloplasticity”）。在这里，动力学的匹配对的聚阳离子，聚（甲基丙烯酰氨丙基三甲基氯化铵），和聚阴离子，聚（甲基丙烯酸酯），分子量大大高于缠结浓度，测量作为温度和盐浓度的函数。还测定了佩奇中NaCl离子的动力学，并与控制粘度的节段弛豫时间相关。一套弛豫时间对应的离子，单体，Pol（+）Pol（-）对交换，纠缠，和爬行进行了测定或估计。发现零剪切粘度η（0）是分子量的异常强的函数，其中缩放η（0）类似于M-5。一个聚合物线圈的大小，测量小角中子散射，与新的定量表达式，以提供一个很好的理论拟合实验这种不寻常的缩放。
The spontaneous association of oppositely charged polyelectrolytes is an example of liquid-liquid phase separation. The resulting hydrated polyelectrolyte complexes or coacervates, both termed "PECs", display a wide range of viscosities. In addition to the usual dependence of viscosity on molecular weight and volume fraction expected for condensed neutral polymers, PECs also contain dense charge pairing between positive, Pol(+), and negative, Pol(-), repeat units. These "stickers" slow polymer chain dynamics on multiple length scales. Pol(+)Pol(-) charge pairs may be broken by the addition of salt to solutions contacting PECs, reducing viscosity ("saloplasticity"). Here, the dynamics of matched pairs of a polycation, poly(methacryloylaminopropyltrimethylammonium chloride), and polyanion, sodium poly(methacrylate), with molecular weights considerably above the entanglement concentration, were measured as a function of temperature and salt concentration. The dynamics of NaCl ions in PECs were also determined and correlated to the segmental relaxation times, which control viscosity. A suite of relaxation times corresponding to ion, monomer, Pol(+)Pol(-) pair exchange, entanglement, and reptation was determined or estimated. The zero-shear viscosity, eta(0), was found to be an unusually strong function of molecular weight, with the scaling eta(0) similar to M-5. A polymer coil size, measured by small-angle neutron scattering, was used in concert with new quantitative expressions to provide a good fit of theory to experiment for this unusual scaling.