Zhang Ren, Lee Bongjoon, Stafford Christopher M, Douglas Jack F, Dobrynin Andrey V, Bockstaller Michael R, Karim Alamgir
College of Polymer Science and Polymer Engineering, The University of Akron, Akron, OH 44325.
Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, PA 15213.
Proc Natl Acad Sci U S A. 2017 Mar 7;114(10):2462-2467. doi: 10.1073/pnas.1613828114. Epub 2017 Feb 22.
The modification of nanoparticles with polymer ligands has emerged as a versatile approach to control the interactions and organization of nanoparticles in polymer nanocomposite materials. Besides their technological significance, polymer-grafted nanoparticle (PGNP) dispersions have attracted interest as model systems to understand the role of entropy as a driving force for microstructure formation. For instance, densely and sparsely grafted nanoparticles show distinct dispersion and assembly behaviors within polymer matrices due to the entropy variation associated with conformational changes in brush and matrix chains. Here we demonstrate how this entropy change can be harnessed to drive PGNPs into spatially organized domain structures on submicrometer scale within topographically patterned thin films. This selective segregation of PGNPs is induced by the conformational entropy penalty arising from local perturbations of grafted and matrix chains under confinement. The efficiency of this particle segregation process within patterned mesa-trench films can be tuned by changing the relative entropic confinement effects on grafted and matrix chains. The versatility of topographic patterning, combined with the compatibility with a wide range of nanoparticle and polymeric materials, renders SCPINS (soft-confinement pattern-induced nanoparticle segregation) an attractive method for fabricating nanostructured hybrid films with potential applications in nanomaterial-based technologies.
用聚合物配体修饰纳米粒子已成为一种通用方法，用于控制聚合物纳米复合材料中纳米粒子的相互作用和组织。除了其技术意义外，聚合物接枝纳米粒子（PGNP）分散体作为模型系统也引起了人们的兴趣，以了解熵作为微观结构形成驱动力的作用。例如，由于与刷状链和基体链构象变化相关的熵变，密集接枝和稀疏接枝的纳米粒子在聚合物基质中表现出不同的分散和组装行为。在这里，我们展示了如何利用这种熵变将PGNP驱动到具有地形图案的薄膜内亚微米尺度的空间组织域结构中。PGNP的这种选择性分离是由受限条件下接枝链和基体链的局部扰动引起的构象熵罚诱导的。通过改变对接枝链和基体链的相对熵限制效应，可以调节图案化台面-沟槽薄膜内这种粒子分离过程的效率。地形图案化的多功能性，结合与广泛的纳米粒子和聚合物材料的兼容性，使SCPINS（软限制图案诱导的纳米粒子分离）成为一种有吸引力的方法，用于制造具有纳米材料基技术潜在应用的纳米结构混合薄膜。
