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Evaluating the Dispersant Stabilization of Colloidal Suspensions from the Scaling Behavior of Gel Rheology and Adsorption Measurements
Langmuir ( IF 3.7 ) Pub Date : 2017-11-14 00:00:00 , DOI: 10.1021/acs.langmuir.7b03343 Fatemeh Khalkhal 1 , Ajay Singh Negi 1 , James Harrison 2 , Casey D. Stokes 2 , David L. Morgan 2 , Chinedum O. Osuji 1
Langmuir ( IF 3.7 ) Pub Date : 2017-11-14 00:00:00 , DOI: 10.1021/acs.langmuir.7b03343 Fatemeh Khalkhal 1 , Ajay Singh Negi 1 , James Harrison 2 , Casey D. Stokes 2 , David L. Morgan 2 , Chinedum O. Osuji 1
Affiliation
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Maintaining suspension stability by effective particle dispersion in systems with attractive interactions can be accomplished by the addition of dispersants that modify the interparticle potential to provide steric or electrostatic barriers against aggregation. The efficacy of such dispersants is typically considered simply by the modification of suspension rheological properties as a function of the overall added dispersant concentration. However, such considerations do little to reveal the molecular origin of differences in dispersant efficacy because they do not consider differences in surface activity. We combine measured adsorption isotherms with the rheological characterization of the elasticity of colloidal gels formed by particle aggregation to provide a more meaningful assessment of dispersant efficacy. The rheological data show that the dispersants are effective at reducing particle aggregation, whereas, from the adsorption isotherms, they differ considerably in their surface coverage at constant overall concentration. When compared at constant dispersant particle surface coverage, the gel rheology shows marked differences across the different dispersants, as opposed to comparisons at constant overall dispersant concentration in the suspensions. In particular, the power-law volume fraction scaling of gel elasticity at constant coverage reveals clear differences in the critical volume fraction for gel formation for the different dispersants. The most efficacious dispersant is that associated with the largest critical volume fraction for gel formation at a given surface coverage. This work demonstrates the utility of rheological investigations coupled with accurate determinations of surface coverage to better differentiate dispersant performance, which may improve efforts to engineer new dispersant molecules.
中文翻译：
从胶体流变的比例行为和吸附测量评估胶体悬浮液的分散稳定性
通过在具有吸引力的相互作用的系统中通过有效的颗粒分散来保持悬浮液的稳定性，可以通过添加分散剂来实现，该分散剂会改变颗粒间的电势，从而提供针对聚集的空间或静电屏障。通常通过改变悬浮液的流变性质作为总添加的分散剂浓度的函数来简单地考虑这种分散剂的功效。但是，由于这些考虑因素并未考虑表面活性的差异，因此它们几乎不能揭示分散剂功效差异的分子来源。我们将测得的吸附等温线与颗粒聚集形成的胶体凝胶的流变学特性相结合，以提供对分散剂功效的更有意义的评估。流变学数据表明，分散剂在减少颗粒聚集方面是有效的，而从吸附等温线来看，它们在总浓度恒定的情况下其表面覆盖率差异很大。当在恒定的分散剂颗粒表面覆盖率下进行比较时，与在悬浮液中恒定的总分散剂浓度下进行比较相比，凝胶流变学显示出不同分散剂之间存在显着差异。特别地，在恒定覆盖率下凝胶弹性的幂律体积分数定标揭示了对于不同分散剂的凝胶形成的临界体积分数的明显差异。最有效的分散剂是在给定的表面覆盖范围内与凝胶形成所需的最大临界体积分数相关的分散剂。
更新日期：2017-11-14
中文翻译：
从胶体流变的比例行为和吸附测量评估胶体悬浮液的分散稳定性
通过在具有吸引力的相互作用的系统中通过有效的颗粒分散来保持悬浮液的稳定性，可以通过添加分散剂来实现，该分散剂会改变颗粒间的电势，从而提供针对聚集的空间或静电屏障。通常通过改变悬浮液的流变性质作为总添加的分散剂浓度的函数来简单地考虑这种分散剂的功效。但是，由于这些考虑因素并未考虑表面活性的差异，因此它们几乎不能揭示分散剂功效差异的分子来源。我们将测得的吸附等温线与颗粒聚集形成的胶体凝胶的流变学特性相结合，以提供对分散剂功效的更有意义的评估。流变学数据表明，分散剂在减少颗粒聚集方面是有效的，而从吸附等温线来看，它们在总浓度恒定的情况下其表面覆盖率差异很大。当在恒定的分散剂颗粒表面覆盖率下进行比较时，与在悬浮液中恒定的总分散剂浓度下进行比较相比，凝胶流变学显示出不同分散剂之间存在显着差异。特别地，在恒定覆盖率下凝胶弹性的幂律体积分数定标揭示了对于不同分散剂的凝胶形成的临界体积分数的明显差异。最有效的分散剂是在给定的表面覆盖范围内与凝胶形成所需的最大临界体积分数相关的分散剂。
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