Monte Carlo simulations of a polyoxyethylene C12E2 lamellar bilayer in water

Abstract

The polyoxyethylene C12E2/ water lamellar phase has been modelled as an aqueous region sandwiched by two bilayers. The bilayers were represented as ethoxy chains attached to a hydrocarbon continuum. Initially, the bilayer separation distance was fixed at 24 A, which is a typical experimental value for the surfactant weight fraction of 71%. Both canonical and Gibbs ensemble simulations have been performed on the system at different temperatures ranging from 298⋅15 K to 353⋅15 K. In the Gibbs simulations the bilayer separation was allowed to readjust to an equilibrium value. The results are compared and contrasted with previous studies in which single chains (Kong, Y. C., Nicholson, D., Parsonage, N. G., and Thompson, L., 1994, J. chem Soc. Faraday Trans, 90, 2375) and charged OH groups (Cracknell, R. F., Nicholson, D., and Parsonage, N. G., 1992, Molec. Phys., 75, 1023), attached to a hydrocarbon substrate, were simulated. As in the previous work with single chains, there is evidence of water bridging whic...