Film Growth and Surface Roughness With Effective Fluctuating Covalent Bonds In Evaporating Aqueous Solution of Reactive Hydrophobic and Polar Groups: A Computer Simulation Model

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Physics and Astronomy


A computer simulation model is proposed to study film growth and surface roughness in aqueous (A) solution of hydrophobic (H) and hydrophilic (P) groups on a simple three dimensional lattice of size L-x x L-y x L-z with an adsorbing Substrate. Each group is represented by a particle with appropriate characteristics occupying a unit cube (i.e., eight sites). The Metropolis algorithm is used to move each particle stochastically. The aqueous Constituents are allowed to evaporate while the concentration of H and P is constant. Reactions proceed from the substrate and bonded particles can hop within a fluctuating bond length. The film thickness (h) and its interface width (W) are examined for hardcore and interacting particles for a range of temperature (T). Simulation data show a rapid increase in h and W followed by its non-monotonic growth and decay before reaching steady-state and near equilibrium (h(s), W-s) in asymptotic time step limit. The growth can be described by power laws, e.g., h alpha t(gamma). W alpha t(beta) with a typical value of gamma approximate to 2, beta approximate to 1 in initial time regime followed by gamma approximate to 1.5, beta approximate to 0.8 at T = 0.5. For hardcore system, the equilibrium film thickness (h(s)) and surface roughness (w(s)) seem to scale linearly with the temperature, i.e., h(s) = 6.206 + 0.302T, W-s = 1255 + 0.425T at low T and h(s) = 6.54 + 0.198T, W-s = 1.808 + 0.202T at higher T. For interacting functional groups in contrast, the long time (unsaturated) film thickness and surface roughness, h(s) and W-s decay rapidly followed by a slow increase on raising the temperature.

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Macromolecular Theory and SImulations





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