  We report the results of large scale Monte Carlo (MC) simulations of novel
microscopic models of gemini surfactants to elucidate (i) their spontaneous
aggregation in bulk water and (ii) their spatial organization in a system where
water is separated from the air above it by a sharp well defined interface. We
study the variation of the critical micellar concentration (CMC) with the
variation of the (a) length of the spacer, (b) length of the hydrophobic tail
and (c) the bending rigidity of the hydrocarbon chains forming the spacer and
the tail; some of the trends of variation are counter-intuitive but are in
excellent agreement with the available experimental results. Our simulations
elucidate the effects of the geometrical shape, size and density of the
surfactant molecules, the ionic nature of the heads and
hydrophobicity/hydrophilicity of the spacer not only on the shapes of the
micellar aggregates and the magnitude of the CMC, but also on their
conformations close to the air-water interface.
