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    Interfacial Rearrangements of Block Copolymer Micelles Toward Gelled Liquid-Liquid Interfaces with Adjustable Viscoelasticity

    Year: 2022

    Journal: Small, Volume 18, MAY

    Authors: Prasser, Quinn; Steinbach, Daniel; Muench, Alexander S.; Neubert, Richard; Weber, Christian; Uhlmann, Petra; Mertens, Florian; Plamper, Felix A.

    Organizations: German Research Foundation (Deutsche Forschungsgemeinschaft DFG) [PL 571/4-1, PL 571/5-1]; Federal Ministry for Economic Affairs and Climate Action (BMWK) of Germany [AiF-IGF 52EWBG/1]; State of Saxony; DFG [PE 1160/26-1]; Projekt DEAL

    Keywords: gels; interfacial rheology; monolayers; polymers; self-assembly

    Though amphiphiles are ubiquitously used for altering interfaces, interfacial reorganization processes are in many cases obscure. For example, adsorption of micelles to liquid-liquid interfaces is often accompanied by rapid reorganizations toward monolayers. Then, the involved time scales are too short to be followed accurately. A block copolymer system, which comprises poly(ethylene oxide)(110)-b-poly{[2-(methacryloyloxy)ethyl]diisopropylmethylammonium chloride}(170) (i.e., PEO110-b-qPDPAEMA(170) with quaternized poly(diisopropylaminoethyl methacrylate)) is presented. Its reorganization kinetics at the water/n-decane interface is slowed down by electrostatic interactions with ferricyanide ([Fe(CN)(6)](3-)). This deceleration allows an observation of the restructuring of the adsorbed micelles not only by tracing the interfacial pressure, but also by analyzing the interfacial rheology and structure with help of atomic force microscopy. The observed micellar flattening and subsequent merging toward a physically interconnected monolayer lead to a viscoelastic interface well detectable by interfacial shear rheology (ISR). Furthermore, the gelled interface is redox-active, enabling a return to purely viscous interfaces and hence a manipulation of the rheological properties by redox reactions. Additionally, interfacial Prussian blue formation stiffens the interface. Such manipulation and in-depth knowledge of the rheology of complex interfaces can be beneficial for the development of emulsion formulations in industry or medicine, where colloidal stability or adapted permeability is crucial.
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