Suspensions of polymer-grafted nanoparticles with added polymers-Structure and effective pair-interactions
Suspensions of polymer-grafted nanoparticles with added polymers-Structure and effective pair-interactions
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DOI：
10.1063/1.4929438
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发表时间：
2015-08-28
影响因子：
4.4
通讯作者：
Basu, J. K.
中科院分区：
文献类型：
--
作者：
Chandran, Sivasurender;Saw, Shibu;Basu, J. K.
我们提出的结果相结合的实验和理论（分子动力学模拟和积分方程理论）研究的结构和有效的相互作用的悬浮液的聚合物接枝纳米粒子（PGNP）在线性聚合物的存在下。由于缺乏系统的实验和理论研究的PGNP，人们普遍认为，在这种二元混合物的结构和有效的相互作用将非常类似的软胶体材料-星型聚合物。在我们的研究中，将官能度f = 70的聚苯乙烯接枝的金纳米颗粒与两种不同分子量的线性聚苯乙烯（PS）混合，以获得两种PGNP：PS尺寸比，xi = 0.14和2.76（其中，xi = M-g/M-m，M-g和M-m分别为接枝聚合物和基质聚合物的分子量）。PGNP的实验结构因子可以用有效势（Model-X）来模拟，这已被发现广泛适用于星星聚合物。类似地，xi = 0.14的共混物的结构因子可以合理地建模，而xi = 2.76的共混物的结构不能被捕获，特别是对于高密度的添加聚合物。在基体聚合物的熔体中PGNP之间的有效相互作用的模型（模型-Y）也未能提供与具有xi = 2.76和高密度添加的聚合物的样品的实验数据的良好一致性。我们尝试性地将这种异常归因于模型X在将添加的聚合物描述为官能度为2的星星聚合物时的可疑假设，该假设在聚合物-聚合物和聚合物-PGNP相互作用中得到体现，特别是在添加的聚合物的较高分数下。Y模型的失败可能是由于当添加的聚合物比例很高时，忽视了由基质聚合物介导的PGNP之间可能的多体相互作用。这些观察结果表明，需要一个新的框架，不仅要了解PGNP的结构行为，而且可能还要了解它们的动力学和热机械性能。(C)2015 AIP Publishing LLC.
We present the results of combined experimental and theoretical (molecular dynamics simulations and integral equation theory) studies of the structure and effective interactions of suspensions of polymer grafted nanoparticles (PGNPs) in the presence of linear polymers. Due to the absence of systematic experimental and theoretical studies of PGNPs, it is widely believed that the structure and effective interactions in such binary mixtures would be very similar to those of an analogous soft colloidal material-star polymers. In our study, polystyrene-grafted gold nanoparticles with functionality f = 70 were mixed with linear polystyrene (PS) of two different molecular weights for obtaining two PGNP: PS size ratios, xi = 0.14 and 2.76 (where, xi = M-g/M-m, M-g and M-m being the molecular weights of grafting and matrix polymers, respectively). The experimental structure factor of PGNPs could be modeled with an effective potential (Model-X), which has been found to be widely applicable for star polymers. Similarly, the structure factor of the blends with xi = 0.14 could be modeled reasonably well, while the structure of blends with xi = 2.76 could not be captured, especially for high density of added polymers. A model (Model-Y) for effective interactions between PGNPs in a melt of matrix polymers also failed to provide good agreement with the experimental data for samples with xi = 2.76 and high density of added polymers. We tentatively attribute this anomaly in modeling the structure factor of blends with xi = 2.76 to the questionable assumption of Model-X in describing the added polymers as star polymers with functionality 2, which gets manifested in both polymer-polymer and polymer-PGNP interactions especially at higher fractions of added polymers. The failure of Model-Y may be due to the neglect of possible many-body interactions among PGNPs mediated by matrix polymers when the fraction of added polymers is high. These observations point to the need for a new framework to understand not only the structural behavior of PGNPs but also possibly their dynamics and thermo-mechanical properties as well. (C) 2015 AIP Publishing LLC.