Aqueous Polyelectrolyte Electrodeposition: The Effects of Alkyl Substitution and Varying Supporting Electrolyte Concentrations on the Deposition Efficiency

Abstract

The controlled growth of surface‐modifying polymer films by electrodeposition often fails because of the lack of redox activity of these compounds. Here, electroactive complexants help to electrodeposit non‐electroactive polymers. Hence, we investigate the counterion‐induced electrodeposition of polyelectrolytes: three quaternized poly(N,N‐dialkylaminoethyl methacrylate)s (qPDAAEMA), in particular their methyl, ethyl, and isopropyl derivatives (i. e. qPDMAEMA, qPDEAEMA, and qPDPAEMA), provide transparent solutions in the presence of hexacyanoferrate(II) (ferrocyanide) at specific concentration windows of the KCl supporting electrolyte. Below a certain KCl concentration, insolubility dominates irrespective of the hexacyanoferrate valency, whilst above an upper threshold, full solubility is observed. Between these limits, oxidation reversibly electrodeposits polymer/hexacyanoferrate(III) (ferricyanide) complexes. Hydrodynamic voltammetry (and data analysis using in‐house software) provides access to the deposition efficiency (DE). qPDEAEMA with ethyl substituents shows highest DEs; larger or smaller substituents fall short because of a balance between “hydrophobicity” and charge separation, shifting the window toward smaller salt concentrations with increasing alkyl size. We always observe a DE maximum close to the minimum salt concentration, whilst electrochemical quartz crystal microbalance (EQCM) measurements indicate a change in film water content close to the maximum. These effects, being also discussed in terms of polymer conformation, can direct the future engineering of electroassisted coatings.

Nonequilibrium Colloids: Temperature-Induced Bouquet Formation of Flower-like Micelles as a Time-Domain-Shifting Macromolecular Heat Alert

“…The background of the current study is given by previously investigated PEO- b - q PDMAEMA and related polymers being unimolecularly dissolved in the absence of ferricyanide. Addition of multivalent counterions leads to co/self-assembly toward an optically transparent micellar dispersion being stabilized by solvated PEO. , The introduction of PPO derived from commercial poloxamers enables a controlled coagulation of the PBCP above a threshold temperature, leading finally to turbid samples even at temperatures back below the threshold. Hence, the system behaves as a sensor with a memory effect, indicating whether the threshold was surpassed previously.…”