An overview of polymer latex film formation and properties.

The literature on polymer latex film formation has grown enormously in recent times--driven by the need to find alternatives for solvent-based systems with their adverse environmental impacts. Although greater insight has been shown by the use of modern instrumental techniques such as small angle neutron scattering, direct non-radiative energy transfer and atomic force microscopy, the actual mechanisms involved in deforming spherical particles into void-free films are still the subject of controversy and debate. Surfactant-free homopolymer model colloid latices, favoured in academic studies, together with latices containing surfactants whose redistribution can influence film properties, and the more complex copolymer, blended, core-shell and pigmented systems needed to satisfy a full range of film properties are all considered.

The cleaning of polymer colloids.

The current state of knowledge of the cleaning of polymer colloids is reviewed with regard to a wide range of cleaning and characterisation techniques. The type, level and quantity of impurities involved with different polymer latex formulations varies widely. Even for similar formulations, differences in the nature and number of functional groups reported are often a consequence of sometimes subtle differences in the cleaning procedures employed. Not only may surface functionality be affected but also monomer and oligomer extraction procedures may lead to morphological changes in the particles. No single technique alone is likely to be able to remove all impurities. Care is needed to avoid the introduction of new impurities from the equipment, materials and water used as well as possible contamination from atmospheric carbon dioxide, bacteria and fungi. These factors also need to be considered in the storage of latex particle standards.