Modeling the Adsorption of Rheology Modifiers onto Latex Particles Using Coarse-Grained Molecular Dynamics (CG-MD) and Self-Consistent Field Theory (SCFT)
Modeling the Adsorption of Rheology Modifiers onto Latex Particles Using Coarse-Grained Molecular Dynamics (CG-MD) and Self-Consistent Field Theory (SCFT)
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DOI：
10.1021/acs.macromol.5b02080
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发表时间：
2015-11-10
期刊：
影响因子：
5.5
通讯作者：
Larson, Ronald G.
中科院分区：
文献类型：
--
作者：
Ginzburg, Valeriy V.;Van Dyk, Antony Keith;Larson, Ronald G.
我们使用粗粒分子动力学（CG-MD）与隐式溶剂和三维自洽场理论（SCFT）与显式溶剂的疏水乙氧基化聚氨酯（HEUR）增稠剂的吸附到两个疏水表面上分离50 nm的画廊。CG-MD模拟可以很容易地扩展到包括非常长的HEUR链（高达540个EO基团），但不能用当前的计算机速度模拟具有长于12个碳（C12）的疏水物的HEUR的吸附。SCFT方法可以很容易地模拟具有较长C16疏水物的HEUR，但模拟非常长的EO链具有更大的挑战。对于具有180个EO单元和C8和C12疏水物的HEUR，可以应用两种方法，允许两种方法的组合跨越实验者感兴趣的大部分参数空间。结果表明，根据疏水强度和HEUR浓度，HEUR链可以直接或间接吸附到表面（作为吸附胶束或admicelles）。我们发现，对于疏水物作为大或大于C12胶束化和随后的吸附胶束发挥了重要作用，在准确预测吸附等温线和吸附层的结构，胶束在溶液中形成节点，允许两个或更多的HEUR链桥接两个表面之间的画廊。这项研究表明，需要调查的影响，admicelles的有效空间相互作用的潜力，这反过来又会影响胶体的稳定性和流变性的HEUR增稠乳胶漆。
We model the adsorption of hydrophobically ethoxylated urethane (HEUR) thickeners onto two hydrophobic surfaces separated by a 50 nm gallery using coarse-grained molecular dynamics (CG-MD) with implicit solvent and three-dimensional self-consistent field theory (SCFT) with explicit solvent. The CG-MD simulations can be readily extended to encompass very long HEUR chains (up to 540 EO groups) but cannot with current computer speed simulate adsorption of HEURs with hydrophobes longer than 12 carbons (C12). The SCFT method can readily simulate HEURs with longer, C16, hydrophobes but has a greater challenge simulating very long EO chains. For HEURs with 180 EO units and C8 and C12 hydrophobes, both methods can be applied, allowing a combination of the two methods to span much of the parameter space of interest to experimentalists. It is demonstrated that depending on the hydrophobe strength and the HEUR concentration, HEUR chains can adsorb to the surfaces directly or indirectly (as adsorbed micelles or admicelles). We show that for hydrophobes as large or larger than C12 micellization and subsequent adsorption of the micelles play an important role in accurate prediction of adsorption isotherms and the structure of adsorbed layers and that micelles in solution form nodes that allow two or more HEUR chains to bridge the gallery between the two surfaces. The study suggests the need to investigate the influence of admicelles on the effective steric interaction potential, which, in turn, will influence both colloidal stability and rheology of HEUR thickened latex paints.