Shrinking of ultrathin polyelectrolyte multilayer capsules upon annealing:A confocal laser scanning microscopy and scanning force microscopy study

Heating-induced morphological changes of micrometer size capsules prepared by step-wise deposition of oppositely charged polyelectrolytes onto melamin e formaldehyde (MF) latex particles and biological cells with subsequent di ssolution of the core have been investigation by confocal laser scanning mi croscopy (CLSM) and scanning force microscopy (SFM). For poly(styrenesulfon ate-Na salt)/poly(allylamine hydrochloride) polyelectrolyte capsules a rema rkable heating-induced shrinking is observed. An increase of the wall thick ness corresponding to the capsule diameter decrease is found. The morpholog y of these microcapsules after temperature treatment is characterized. The thickening of the polyelectrolyte multilayer is interpreted in terms of a c onfigurational entropy increase via polyanion-polycation bond rearrangement .