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• Microgels based on poly(acrylic acid modified with dopamine) and crosslinked with BAC were synthesized. • Microgel particles formed stable monolayers on Au microelectrode surface through chemisorption. • Modified microelectrode was electroactive and made a good electrochemical pH sensor. A novel electroactive and pH-responsive microgel was successfully synthesized. The obtained microgel was based on acrylic acid, dopamine methacrylamide and N,N′ -bis(acryloyl)cystamine as the crosslinker. Using the distillation precipitation polymerization method, spherical, smooth-surface microgel particles of ca. 400 nm in diameter were obtained. The presence of dopamine groups in the polymer network was confirmed with cyclic voltammetry and NMR spectroscopy. The dependence of microgel hydrodynamic diameter on pH was investigated using the DLS technique. The presence of -S–S- groups in the microgel particle was used to modify the Au electrode surface by chemisorption. The attachment was monitored with the QCM-D technique. The obtained microgel was successfully anchored to the Au regular- and microelectrode surfaces. The electrochemical properties of the modified electrodes were promising. It was found that modified electrodes exhibited potentially useful pH-sensing properties. Modification of Au microelectrode surface with the environmentally sensitive and electroactive microgel monolayer is a novel, innovative approach. [ABSTRACT FROM AUTHOR]

[Display omitted] • The pH-sensitive microgel based on acrylic acid cross-linked with -S S- was obtained. • The microgel particles were attached to the Au electrode by chemisorption. • pH during modification strongly affected the structure of the microgel monolayer. • pH had a very strong effect on the voltammetric response of the modified electrode. • The switching behavior of the electrode was fully reversible and relatively fast. In this work, we present the use of pH-sensitive microgel based on acrylic acid crosslinked with N,N′- bis(acryloyl)cystamine in the modification of Au electrode surface through the chemisorption process. The strong interactions between the crosslinker disulfide bridges and the gold surface were employed. The shape and morphology of the microgel particles were determined using scanning electron microscopy (SEM). The gel sensitivity to pH was examined using the dynamic light scattering technique (DLS). The impact of pH on electrode processes at the modified Au surface was studied using cyclic voltammetry (CV). It was found that at appropriate pH the microgel particles formed a loose monolayer on the electrode surface, which, in the swollen state, was able to block the transport of negatively charged redox probe to the electrode surface. On the other hand, when the microgels were in the shrunken state, the electrode surface was partially uncovered, and that allowed the redox probe to reach the electrode surface. The anchoring process of the microgels on the Au electrode surface was monitored with a quartz crystal microbalance with dissipation technique (QCM-D). The electrochemical properties of the modified with the pH-sensitive microgel layer electrodes were examined in the presence of either positively or negatively charged redox probes using CV and electrochemical impedance spectroscopy (EIS). It turned out that the electrochemical signals were strongly affected by both: degree of swelling of the microgel and protonation of the carboxylic groups of acrylic acid in the polymer network. The switching of electrode behavior was fully reversible and relatively fast. [ABSTRACT FROM AUTHOR]

We present a novel microgel with the capacity for self-assembly, the volume of which can be altered by performing the appropriate redox reaction. The initial thermoresponsive microgel was synthesized from N -isopropylacrylamide and N -(3-aminopropyl)methacrylamide, with N,N′ -bisacryloylcystine used as the crosslinker. The obtained microgel polymer network was modified with benzoquinone through the Aza-Michael addition reaction. The influence of the redox state of the benzoquinone groups in the microgel on volume phase transition temperature was examined. The disulfide bridges from the N,N′ -bisacryloylcystine linker were used to attach microgel particles on an Au electrode surface, forming a monolayer. The monolayer formation and the volume phase transition within the microgel were monitored with the QCM technique. The redox state of the electroactive benzoquinone groups in the polymer network appeared to be the key factor determining whether the microgel layers exist in the shrunken or swollen state. The oxidation state can be changed electrochemically and the shrinking-swelling transformation was shown to be reversible. The obtained material was also studied with dynamic light scattering technique and electron microscopies. [Display omitted] • Thermosensitive microgel containing benzoquinone groups was obtained. • VPTT strongly dependent on the oxidation state of the quinone groups. • Disulfide bridges present in the microgel allowed to form monolayer on Au surface. • The size of the microgel monolayer can be controlled electrochemically. [ABSTRACT FROM AUTHOR]

Electroactive, electrosensitive and fast reacting p(AA-BAC)/Cu(II) microlayers were successfully constructed on the Au electrode surface. The layers consisted of microgel particles composed of poly(acrylic acid) cross-linked with N,N-bis(acryloyl)cystamine (BAC). The p(AA-BAC) microgels were synthesized using distillation precipitation polymerization. The deposition of microgels was due to chemisorption of -S-S- groups from BAC on the gold surface. After the deposition, copper(II) ions were added and bound with the polymer network through the coordination bonds with the carboxylic groups. This addition increased the number of crosslinking points in the gel. The microgel particles were characterized using SEM, QCM-D, dynamic light scattering and electrochemistry. Thanks to reversibility of the electroreduction and electrooxidation of the copper ions (from Cu(II) to Cu(I) and from Cu(I) to Cu(II)) the obtained layers of p(AA-BAC)/Cu(II) microparticles on gold could undergo multiple fast swelling and shrinking processes triggered by application of appropriate sequence of potentials. [ABSTRACT FROM AUTHOR]