Ordering of latex particles during film formation

Small angle neutron scattering and electron microscopy are used to investigate the ordering of soft latex particles which have been dispersed in water and then brought into contact through evaporation of the solvent. We observe a succession of metastable states where the particles are kept separated by their hydrophilic surface layers: colloidal liquid (short range order only) to colloidal crystal (long range order) to foam (dense packing of polyhedral cells with latex interior and hydrophilic walls). At each stage the structure may collapse into a homogeneous latex phase through coalescence of the particles and expulsion of the hydrophilic material.