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Reverse Monte Carlo simulations have been carried out to provide molecular-level detail on the structures of three different lipid and surfactant monolayers of particular relevance in the design and development of drugs and drug delivery systems. The simulations were performed using the SURFISS program, with the orientations and conformations of the molecules in the monolayers optimised iteratively using constraints furnished from neutron reflectance-derived volume fraction profile data. The three systems modelled involve the monolayers formed at the air/water interface by the synthetic surfactants N,N-dimethyldodecylamine-N-oxide and 1,2-di-O-octadecyl-rac-glyceryl-3-(ω-methoxydodecaoxyethylene) and the self-assembled layer of dimyristoylphosphatidylcholine adsorbed onto silicon hydrophobized by treatment with octadecyltrichlorosilane

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A molecular modeling program, SURFISS, is described which allows for the generation of representative configurations of surfactant molecules organized as planar monolayers at an air−liquid interface. The monolayer structures are generated by means of a conformational search optimization procedure using constraints derived from the data obtained in neutron reflectivity experiments. The utility of the program is demonstrated through successful simulations carried out for monolayers formed from the nonionic surfactant monododecyl hexaethylene glycol (C12E6) and the cationic surfactant hexadecyl trimethylammonium bromide (C16TAB).