ABSTRACT
Molecular dynamics (MD) simulations were used to predict the wetting behavior of materials typical of active and hole-transport layers in organic electronics by evaluating their contact angles and adhesion energies. The active layer (AL) here consists of a blend of poly(3-hexylthiophene) and phenyl-C61-butyric acid methyl ester (P3HT:PCBM), whereas the hole-transport layer (HTL) consists of a blend of poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonate) (PEDOT:PSS). Simulations of the wetting of these surfaces by multiple solvents show that formamide, glycerol, and water droplet contact angle trends correlate with experimental values. However, droplet simulations on surfaces are computationally expensive and would be impractical for routine use in printed electronics and other applications. As an alternative, contact angle measurements can be related to adhesion energy, which can be calculated more quickly and easily from simulations and has been shown to correlate with contact angles. Calculations of adhesion energy for 16 different solvents were used to rapidly predict the wetting behavior of solvents on the AL and HTL surfaces. Among the tested solvents, pentane and hexane exhibit low and similar adhesion energy on both of the surfaces considered. This result suggests that among the tested solvents, pentane and hexane exhibit strong potential as orthogonal solvent in printing electronic materials onto HTL and AL materials. The simulation results further show that MD can accelerate the evaluation of processing parameters for printed electronics.
ABSTRACT
Composites of hydroxyapatite and polymers are widely studied for bone replacement. To perform satisfactorily in the human body, these composites need to be biocompatible and exhibit optimum mechanical properties. The load-deformation behavior of composites is often investigated using experimental techniques. However, the molecular mechanisms of load deformation behavior are not clearly understood. We have used Steered Molecular Dynamics to evaluate the load-deformation behavior at interfaces in polyacrylic acid-hydroxyapatite (HAP) composite models. The polymer is pulled at constant velocity in close proximity of HAP. On comparing the results obtained for deformation behavior of polymer in vicinity of mineral and in the absence of mineral, it was found that energy required to pull the polymer in close proximity of HAP is significantly higher. Also, structural details of the load transfer mechanisms in composite were investigated under both conditions. Our simulations indicate that there is a significant role of mineral-polymer interactions on the mechanical response of polymer.
