In this work, we propose computational methods for investigating the fundamentals of adhesion behaviors at organic-inorganic interface. The structural integrity at such interface is critical because the quality of such system largely depends on how adhesion is managed. Within this context, detailed investigation of the interfacial adhesion and its quantification are important aspects. In experiments, the peeling and pulling tests are commonly performed but they cannot provide comprehensive view on the degree of plastic deformation and the effect from different patterns of mechanical loading. This can be overcome by computing the thermodynamic work of adhesion by separating the interface within atomistic simulation. Hence, we develop three different adhesion measurement techniques- pulling, peeling, and sliding within steered molecular dynamics. Such methodologies can be applied to investigate heterogeneous materials (e.g., polyimide detachment from silica during flexible display manufacturing process). Current studies indicate that the pulling test requires the largest force and the shortest distance to detachment as the interfacial area is separated instantaneously, while the peeling test is observed to exhibit the largest distance for detachment. Two kinds of polyimides, aromatic and aliphatic type, are considered to demonstrate the rigidity dependent adhesion properties. The aromatic polyimide, which is more rigid due to the stronger charge transfer complex between chains, requires a greater force but a smaller distance at detachment than the aliphatic polyimide. We further apply the developed methods to design a novel polymeric binder for improving performance of the future generation of silicon based anodes, suffering from their huge volume change during the electrochemical cycling. We investigate the role of functional groups in the polymeric binder on the structural stability of LixSiO2. A pulling test reveals that the binder with the polar group shows better adhesion properties with LixSiO2 than that with the nonpolar group. In addition, the adhesive failure dominates the failure mode from the polar group but the cohesive to adhesive failure shift occurs from the nonpolar group. We believe that developed modeling capabilities can be towards assessing functional performance of several types of organic-inorganic multilayers, which are increasingly becoming an integral part of various electronic/electrochemical devices.

Computational approaches for investigating adhesion phenomena at organic-inorganic interface

256th National Meeting (2018)

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