INVESTIGADORES
RAMIREZ PASTOR antonio Jose
artículos
Título:
Adsorption of self-assembled rigid rods on two-dimensional lattices
Autor/es:
LÓPEZ L. G.; RAMIREZ PASTOR A. J.
Revista:
LANGMUIR
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2012 vol. 28 p. 14917 - 14924
ISSN:
0743-7463
Resumen:
Monte Carlo (MC) simulations have been carried out to study the
adsorption on square and triangular lattices of particles with two
bonding sites that, by decreasing temperature or increasing density,
polymerize reversibly into chains with a discrete number of allowed
directions and, at the same time, undergo a continuous isotropic-nematic
(IN) transition. The process has been monitored by following the
behavior of the adsorption isotherms (chemical potential μ as a function
of the surface coverage θ) for different values of lateral interaction
energy/temperature. The numerical data were compared with mean-field
analytical predictions and exact functions for noninteracting and 1D
systems. The obtained results revealed the existence of three adsorption
regimes in temperature. (1) At high temperatures, above the critical
one characterizing the IN transition at full coverage T c(θ =
1), the particles are distributed at random on the surface and the
adlayer behaves as a noninteracting 2D system. (2) At very low
temperatures, the asymmetric monomers adsorb, forming chains over almost
the entire range of coverage, and the adsorption process behaves as a
1D problem. (3) In the intermediate regime, the system exhibits a mixed
regime and the filling of the lattice proceeds according to two
different processes. In the first stage, the monomers adsorb
isotropically on the lattice until the IN transition occurs in the
system and, from this point, particles adsorb, forming chains so that
the adlayer behaves as a 1D fluid. The two adsorption processes are
present in the adsorption isotherms, and a marked singularity can be
observed that separates both regimes. Thus, the adsorption isotherms
appear as sensitive quantities with respect to the IN phase transition,
allowing us (i) to reproduce the phase diagram of the system for square
lattices and (ii) to obtain an accurate determination of the phase
diagram for triangular lattices. © 2012 American Chemical Society.