Rheological changes and kinetics of water uptake by poly(ionic liquid)-based thin films

One-pot synthesis of magnetic cellulose nanocrystal and its post-functionalization for doxycycline adsorption

The composite of magnetite (Fe₃O₄) and cellulose nanocrystal (CNC) is considered a potential adsorbent for water treatment and environmental remediation. In the current study, a one-pot hydrothermal procedure was utilized for magnetic cellulose nanocrystal (MCNC) development from microcrystalline cellulose (MCC) in the presence of ferric chloride, ferrous chloride, urea, and hydrochloric acid. The x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy analysis confirmed the presence of CNC and Fe₃O₄, while transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis verified their respective sizes (< 400 nm and ≤ 20 nm) in the generated composite. To have an efficient adsorption activity for doxycycline hyclate (DOX), the produced MCNC was post-treated using chloroacetic acid (CAA), chlorosulfonic acid (CSA), or iodobenzene (IB). The introduction of carboxylate, sulfonate, and phenyl groups in the post-treatment was confirmed by FTIR and XPS analysis. Such post treatments decreased the crystallinity index and thermal stability of the samples but improved their DOX adsorption capacity. The adsorption analysis at different pHs revealed the increase in the adsorption capacity by reducing the basicity of the medium due to decreasing electrostatic repulsions and inducing strong attractions.

Downplaying the role of water in the rheological changes of conducting polymers by using water-in-salt electrolytes

Volumetric changes associated with solvent/electrolyte exchange in electronic conducting polymers (ECPs) play an important role in the mechanical stability of the polymers, as these changes are a critical factor in ECP-based energy storage devices. Thus, the present work explores the hindering of such volumetric deformations for polypyrrole films doped with dodecylbenzenesulphonate (PPy(DBS)) by employing highly concentrated aqueous electrolytes (or water-in-salt electrolytes, WiSEs), and their effects over the corresponding electrochemical capacitor cell energy retention. Electrochemical quartz crystal microbalance with dissipation monitoring measurements for thin PPy(DBS) films in the WiSEs revealed negligible dissipation changes (ΔDn ≈ 0), in contrast with those in dilute aqueous electrolyte (ΔDn ≠ 0), indicating inexpressive structural deformation of PPy(DBS) in the WiSE. This phenomenon is observed for thick freestanding PPy(DBS) films, which presented a maximum bending angle decay from ∼56° (diluted aqueous electrolyte) to 3.5° when working in the WiSE, thus proving the hindering of film bending. The observed trends are reflected in the PPy(DBS) cell energy retention, where the use of a WiSE decreased cell energy fading by 30% after 600 cycles, in comparison with cells based on diluted electrolytes.

Electrochemical quartz crystal microbalance with dissipation investigation of fibronectin adsorption dynamics driven by electrical stimulation onto a conducting and partially biodegradable copolymer

Functional surface coatings are a key option for biomedical applications, from polymeric supports for tissue engineering to smart matrices for controlled drug delivery. Therefore, the synthesis of new materials for biological applications and developments is promising. Hence, biocompatible and stimuli-responsive polymers are interesting materials, especially when they present conductive properties. PEDOT-co-PDLLA graft copolymer exhibits physicochemical and mechanical characteristics required for biomedical purposes, associated with electroactive, biocompatible, and partially biodegradable properties. Herein, the study of fibronectin (FN) adsorption onto PEDOT-co-PDLLA carried out by an electrochemical quartz crystal microbalance with dissipation is reported. The amount of FN adsorbed onto PEDOT-co-PDLLA was higher than that adsorbed onto the Au surface, with a significant increase when electrical stimulation was applied (either at +0.5 or -0.125 V). Additionally, FN binds to the copolymer interface in an unfolded conformation, which can promote better NIH-3T3 fibroblast cell adhesion and later cell development.

Electrically Tunable Soft-Solid Block Copolymer Structural Color

One-dimensional photonic crystals based on the periodic stacking of two different dielectric layers have been widely studied, but the fabrication of mechanically flexible polymer structural color (SC) films, with electro-active color switching, remains challenging. Here, we demonstrate free-standing electric field tunable ionic liquid (IL) swollen block copolymer (BCP) films. Placement of a polymer/ionic liquid film-reservoir adjacent to a self-assembled poly(styrene-block-quaternized 2-vinylpyridine) (PS-b-QP2VP) copolymer SC film allowed the development of red (R), green (G), and blue (B) full-color SC block copolymer films by swelling of the QP2VP domains by the ionic liquid associated with water molecules. The IL-polymer/BCP SC film is mechanically flexible with excellent color stability over several days at ambient conditions. The selective swelling of the QP2VP domains could be controlled by both the ratio of the IL to a polymer in the gel-like IL reservoir layer and by an applied voltage in the range of -3 to +6 V using a metal/IL reservoir/SC film/IL reservoir/metal capacitor type device.

Two phosphonium ionic liquids with high Li+ transport number

This work presents the physicochemical characterization of two ionic liquids (ILs) with small phosphonium cations, triethylpenthylphosphonium bis(trifluoromethanesulfonyl)imide ([P₂₂₂₅][Tf₂N]) and (2-methoxyethyl)trimethylphosphonium bis(trifluoromethanesulfonyl)imide ([P_222(201)][Tf₂N]), and their mixtures with Li⁺.

Adsorption of quantum dots onto polymer and Gemini surfactant films: a quartz crystal microbalance study

We used quartz crystal microbalance with dissipation to study the mechanical properties, the kinetics of adsorption, and the amount of CdSe quantum dots (QDs) adsorbed onto a SiO2 sensor, referred as bare sensor, onto the sensor modified with a film of the polymer poly(maleic anhydride-alt-1-octadecene), PMAO, or with a film of the Gemini surfactant ethyl-bis(dimethyl octadecyl ammonium bromide), abbreviated as 18-2-18. Results showed that when the sensor is coated with polymer or surfactant molecules, the coverage increases compared with that obtained for the bare sensor. On the other hand, rheological properties and kinetics of adsorption of QDs are driven by QD nanoparticles. Thus, the QD films present elastic behavior, and the elasticity values are independent of the molecule used as coating and similar to the elasticity value obtained for QDs films on the bare sensor. The QD adsorption is a two-step mechanism in which the fastest process is attributed to the QD adsorption onto the solid substrate and the slowest one is ascribed to rearrangement movements of the nanoparticles adsorbed at the surface.

Real-time analysis of porphyrin J-aggregation on a plant-esterase-functionalized surface using quartz crystal microbalance with dissipation monitoring

The J-aggregation of meso-tetra (4-sulfonatophenyl) porphine (TPPS4) on a plant-esterase-functionalized surface in a 1:1 v/v mixture of 0.05 M HCl/ethanol (pH ∼1.38) was analyzed in real time using a quartz crystal microbalance with dissipation monitoring (QCM-D). Simultaneous changes in frequency (Δf) and energy dissipation (ΔD) correlated well with mass and structural changes during the sequential phases of slow nucleation, rapid aggregation, and equilibration in J-aggregation. The time-dependent mass adsorption could be quantitatively analyzed with a model, which integrated two simple equations obtained when the surface concentration of TPPS4 (Γ(TPPS4)) was below and above the critical aggregation surface concentration (CASC). This study provides a new view for the protein-induced J-aggregation process, which may be helpful for understanding the interactions of self-assembled nanostructures with biomolecules.

Electronic control over detachment of a self-doped water-soluble conjugated polyelectrolyte

Water-soluble conducting polymers are of interest to enable more versatile processing in aqueous media as well as to facilitate interactions with biomolecules. Here, we report a substituted poly(3,4-ethylenedioxythiophene) derivative (PEDOT-S:H) that is fully water-soluble and self-doped. When electrochemically oxidizing a PEDOT-S:H thin film, the film detaches from the underlying electrode. The oxidation of PEDOT-S:H starts with an initial phase of swelling followed by cracking before it finally disrupts into small flakes and detaches from the electrode. We investigated the detachment mechanism and found that parameters such as the size, charge, and concentration of ions in the electrolyte, the temperature, and also the pH influence the characteristics of detachment. When oxidizing PEDOT-S:H, the positively charged polymer backbone is balanced by anions from the electrolyte solution and also by the sulfonate groups on the side chains (more self-doping). From our experiments, we conclude that detachment of the PEDOT-S:H film upon oxidation occurs in part due to swelling caused by an inflow of solvated anions and associated water and in part due to chain rearrangements within the film, caused by more self-doping. We believe that PEDOT-S:H detachment can be of interest in a number of different applications, including addressed and active control of the release of materials such as biomolecules and cell cultures.