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From Adhesion to Wetting: Contact Mechanics at the Surfaces of Super-Soft Brush-Like Elastomers
ACS Macro Letters ( IF 5.8 ) Pub Date : 2017-07-25 00:00:00 , DOI: 10.1021/acsmacrolett.7b00419
Maria Ina 1 , Zhen Cao 2 , Mohammad Vatankhah-Varnoosfaderani 1 , Matthew H. Everhart 1 , William F. M. Daniel 1 , Andrey V. Dobrynin 2 , Sergei S. Sheiko 1
Affiliation  

Fundamental understanding of rigid particle indentation into soft elastic substrates has been elusive for decades. In conventional heterogeneous and multicomponent systems, the ill-defined interplay between elastic and capillary forces has confounded explanation of the crossover region between the classical wetting and adhesion regimes. Herein, we study the indentation behavior of micrometer-sized silica particles on supersoft, solvent-free PDMS elastomers with brush-like network strands. By varying the side chain grafting density and the cross-linking density of the networks, we control their elastic modulus from ∼1 to 100 kPa without adding solvent. This isostructurally regulated balance between elastic and capillary forces allows for accurate mapping of the entire range of particle–substrate interactions by measuring indentation depth as a function of substrate stiffness and particle radius. A generalized theoretical model, accounting for the collaborative contribution of both forces to the system free energy, demonstrates excellent quantitative agreement with our experimental results as well as with results of computer simulation for particles in contact with soft surfaces.

中文翻译:

从附着力到润湿:超软刷状弹性体表面的接触力学

几十年来,对硬质颗粒压入软弹性基材的基本了解一直难以捉摸。在传统的非均质和多组分系统中,弹性力和毛细力之间不确定的相互作用已经混淆了传统润湿和粘附机制之间交叉区域的解释。在本文中,我们研究了微米级二氧化硅颗粒在超软,无溶剂的PDMS弹性体(具有刷状网络链)上的压痕行为。通过改变网络的侧链接枝密度和交联密度,我们在不添加溶剂的情况下将其弹性模量控制在约1至100 kPa。弹性力和毛细力之间的这种等量调节的平衡可通过测量压痕深度(作为基材刚度和颗粒半径的函数)来精确映射颗粒-基材相互作用的整个范围。一个通用的理论模型,考虑了两种力对系统自由能的协同作用,证明了与我们的实验结果以及与软表面接触的粒子的计算机模拟结果极好的定量一致性。
更新日期:2017-07-25
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