Interdiffusion during film formation of ionically cross-linked acrylics investigated with Förster resonance energy transfer (FRET)
Polymer interdiffusion is crucial to obtain continuous films from aqueous polymer dispersions. Here, interdiffusion in films from dispersions of acrylates which were ionically cross‐linked prior to film formation was studied by Förster resonance energy transfer analysis. Dispersions of copolymers of n‐butyl acrylate, methacrylic acid, and zinc dimethacrylate (ZnDMA) were investigated. ZnDMA was used as a co‐monomer to ionically cross link the polymers during the synthesis. Ionic cross‐linking does not prevent interdiffusion even at high gel contents. Interdiffusion data were compared with results of tensile tests on final films. Films of ionically cross‐linked polymers fracture at both higher stress and strain than films of covalently cross‐linked polymers. Further interdiffusion studies addressed effects of temperature and humidity. Both increased temperature and humidity accelerate interdiffusion of ionically cross‐linked polymers. Thus, using ZnDMA allows for preparing dispersions which can form continuous films. Also, no volatile organic compounds are released during the film formation.