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The incorporation of nanometric size particles in a matrix to form dielectric composites shows promise of materials (nanodielectrics) with new and improved properties. It is argued that the properties of the interfaces between the particles and the matrix, which will themselves be of nanometric dimensions, will have an increasingly dominant role in determining dielectric performance as the particle size decreases. The forces that determine the electrical and dielectric properties of interfaces are considered, with emphasis on the way in which they might influence composite behaviour. A number of examples are given in which interfaces at the nanometric level exercise both passive and active control over dielectric, optical and conductive properties. Electromechanical properties are also considered, and it is shown that interfaces have important electrostrictive and piezoelectric characteristics. It is demonstrated that the process of poling, namely subjecting macroscopic composite materials to electrical stress and raised temperatures to create piezoelectric materials, can be explained in terms of optimizing the collective response of the nanometric interfaces involved. If the electrical and electromechanical features are coupled to the long-established electrochemical properties, interfaces represent highly versatile active elements with considerable potential in nanotechnology.

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Pressure-area isotherms and surface potential data are presented for octadecyl methyl sulphoxide (OMS) and ( + )-octadecyl p-tolyl sulphoxide (OTS). The surface potential measurements indicate very clearly that both compounds are anchored at the water surface by the SO group and that the plateau in the pressure-area isotherm of OTS is the result of significant molecular orientation. The Demchak and Fort model for relating group dipole moments to the surface potential of floating Langmuir monolayers is reviewed and found to be applicable to a number of compounds. However, the values deduced by these authors for the local permittivities are not appropriate for compounds with long aliphatic chains. By drawing on previously published work a new set of values has been deduced which seems to be more applicable to such compounds and to the sulphoxides investigated here.