The layer-by-layer (LbL) technique is a powerful approach to constructing ultrathin polyelectrolyte multilayer films. One key feature of hydrogen-bonded LbL films is that once obtained at low pH, they can be easily erased at a higher pH value as a result of increased ionization of the weak polyacid. The pH-induced charge within hydrogen-bonded films can be used to incorporate oppositely charged functional molecules. These molecules can then be released at a later step in response to further pH variations. Along with pH, temperature is another important stimulus in designing responsive assemblies for biomedical applications. Of specific interest for biomedical applications are water-soluble polymers with a lower critical solution temperature (LCST) close to physiological temperature.
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