Adsorption of Self-AssembledRigid Rodson Two-Dimensional Lattices.

Monte Carlo (MC) simulations have been carried out tostudy theadsorption on square and triangular lattices of particles with twobonding sites that, by decreasing temperature or increasing density,polymerize reversibly into chains with a discrete number of alloweddirections and, at the same time, undergo a continuous isotropic–nematic(IN) transition. The process has been monitored by following the behaviorof the adsorption isotherms (chemical potential μ as a functionof the surface coverage θ) for different values of lateral interactionenergy/temperature. The numerical data were compared with mean-fieldanalytical predictions and exact functions for noninteracting and1D systems. The obtained results revealed the existence of three adsorptionregimes in temperature. (1) At high temperatures, above the criticalone characterizing the IN transition at full coverage Tc(θ = 1), the particles are distributed at randomon the surface and the adlayer behaves as a noninteracting 2D system.(2) At very low temperatures, the asymmetric monomers adsorb, formingchains over almost the entire range of coverage, and the adsorptionprocess behaves as a 1D problem. (3) In the intermediate regime, thesystem exhibits a mixed regime and the filling of the lattice proceedsaccording to two different processes. In the first stage, the monomersadsorb isotropically on the lattice until the IN transition occursin the system and, from this point, particles adsorb, forming chainsso that the adlayer behaves as a 1D fluid. The two adsorption processesare present in the adsorption isotherms, and a marked singularitycan be observed that separates both regimes. Thus, the adsorptionisotherms appear as sensitive quantities with respect to the IN phasetransition, allowing us (i) to reproduce the phase diagram of thesystem for square lattices and (ii) to obtain an accurate determinationof the phase diagram for triangular lattices. [ABSTRACT FROM AUTHOR]