Molecular Parameters Governing the Elastic Properties of Brush Particle Films
Molecular Parameters Governing the Elastic Properties of Brush Particle Films
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DOI：
10.1021/acs.macromol.9b01809
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发表时间：
2020-02-25
期刊：
影响因子：
5.5
通讯作者：
Bockstaller, Michael R.
中科院分区：
文献类型：
--
作者：
Lee, Jaejun;Wang, Zongyu;Bockstaller, Michael R.
阐明了聚合物冠层的组成和结构对刷状颗粒基材料的组装和力学性能的相互影响，有望促进对控制杂化材料相互作用的控制参数的理解和新型功能材料的开发。在这项工作中，三个系列的刷颗粒系统的弹性性能进行了研究，区分为密集，中间和稀疏刷系统的接枝密度。密集和中间系统显示均匀的微观结构，程度的顺序（使用Voronoi细胞面积分析测量）增加接枝密度。对于密集和中间刷颗粒系统，仪器化压痕分析显示的弹性模量的增加与拴系链的聚合度，在有效的介质预测相反。此外，配体对颗粒相互作用的贡献随着接枝密度的降低而增加。结果表明，刷状粒子薄膜在拉伸形变中的响应行为取决于相邻刷状粒子配体间的色散相互作用。在中间接枝密度的情况下，更明显的刷状交错增强了刷状颗粒之间的分散相互作用，因此提高了膜的模量。一个相反的趋势，在薄膜中观察到的稀疏刷颗粒，也具有形成的字符串一样的上层结构。在这里，弹性模量大幅增加低分子配体和连续降低，随着聚合度的增加拴系链沿着与过渡，从字符串状均匀的形态。独立的接枝密度，原始聚合物的弹性模量恢复在聚合物配体的高聚合度的限制。
Elucidation of the mutual influence of composition and architecture of polymer canopies on the assembly and mechanical properties of brush particle-based materials holds the promise of advancing the understanding of the governing parameters controlling interactions in hybrid materials and the development of novel functional materials. In this work, the elastic properties of three series of brush particle systems were investigated, differentiated by grafting density as dense, intermediate, and sparse brush systems. Dense and intermediate systems displayed uniform microstructures; the degree of order (measured using Voronoi cell area analysis) increased with grafting density. For dense and intermediate brush particle systems, instrumented indentation analysis revealed an increase of the elastic modulus with the degree of polymerization of tethered chains, in contrast to effective medium predictions. Furthermore, the contribution of ligands to particle interactions increased with decreasing grafting density. The results indicated that the response behavior of particle brush films in tensile-type deformations depends on dispersion interactions between ligands of adjacent brush particles. The more pronounced brush interdigitation in the case of intermediate graft densities enhanced the dispersion interactions between brush particles and hence the modulus of films. A reversed trend in modulus was observed in films of sparse brush particles that also featured the formation of string-like superstructures. Here, the elastic modulus was substantially increased for low-molecular ligands and continuously decreased with increasing degree of polymerization of tethered chains along with a transition from string-like to uniform morphologies. Independent of grafting density, the elastic modulus of the pristine polymer was recovered in the limit of a high degree of polymerization of polymer ligands.