Humidity-Driven Transparent Holographic Free-Standing Polyelectrolyte Films

In the present work, transparent holographic poly(diallyldimethylammonium chloride) (PDADMAC)/heparin and PDADMAC/poly(styrenesulfonate) (PSS) films were synthesized via polyelectrolyte coacervates. PDADMAC/heparin films were obtained without temperature treatment. Thin holographic free-standing films with a 1 μm grating period and uniform surface of a polyelectrolyte complex were readily and quickly made by pressing polyelectrolyte coacervate, the hydrated viscoelastic fluid-like form of polyelectrolyte complex precursor, between a flat surface and holographic mask. Heparin replaces PSS in film composition to prepare the sheer film. Thus, the PDADMAC/heparin holographic film demonstrates transparency and reversible response for humidity under diffraction detection. In addition to diffraction humidity signal measurements, the cobalt(II) chloride was impregnated in polyelectrolyte coacervate to make an additional colorimetric signal response. In this case, the free-standing film serves both as the substrat...