The behaviour of complex molecules, such as nanoparticles, polymers, and proteins, at liquid interfaces is of increasing importance in a number of areas of science and technology. It has long been recognised that solid particles adhere to liquid interfaces, which provides a convenient method for the preparation of nanoparticle structures or to modify interfacial properties. The adhesion of proteins at liquid interfaces is important in many biological processes and in a number of materials applications of biomolecules. While the reduced dimensions of these particles make experimental investigation challenging, molecular simulations provide a natural means for the study of these systems. In this paper I will give an overview of some recent work using molecular simulation to investigate the behaviour of complex molecules at liquid interfaces, focusing on the relationship between interfacial adsorption and molecular structure, and outline some avenues for future research. 1. Introduction Dating back to the ancient Greeks the interface between immiscible fluids, in particular between oil and water, has been of both scientific and practical interest [1]. As the two liquid components can have radically different properties, the behaviour of molecules in an interfacial environment can differ from bulk solution. For example, molecular recognition driven by hydrogen bonding can be orders of magnitude stronger at the air-water interface than in solution [2, 3], which may be exploited in the formation of ordered materials [4] or the operation of molecular machines at the air-water interface [5]. When additional species are added to the system, these may accumulate at the interface; this is exemplified by amphiphilic surfactants, the adsorption of which to interfaces can be used to modify interfacial properties, such as surface tension. This adsorption of molecules also allows the interfaces to be used as platforms for chemical synthesis [6] and formation of nanoparticles [7]. It has long been recognised that liquid interfaces potentially provide elegant and convenient templates for the construction of dense and ordered structures. While the adsorption and self-assembly of small surfactant molecules have attracted attention over many years, recently the adsorption of larger and more complex molecules, such as nanoparticles, polymers, and proteins, and other biomolecules has attracted attention. For over 100 years it has been known that solid particles can adhere to interfaces between immiscible liquids [8]. This has been exploited in the formation of two-dimensional
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