Controlled Sr(ii) ion release from in situ crosslinking electroactive hydrogels with potential for the treatment of infections

The development of electrochemical stimuli-responsive drug delivery systems is of both academic and industrial interest due to the ease with which it is possible to trigger payload release, providing drug delivery in a controllable manner. Herein, the preparation of in situ forming hydrogels including electroactive polypyrrole nanoparticles (PPy-NPs) where Sr2+ ions are electrochemically loaded for electrically triggered release of Sr2+ ions is reported. The hydrogels were characterized by a variety of techniques including Fourier-transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), cyclic voltammetry (CV), etc. The cytocompatibility towards human mesenchymal stem cells (MSCs) and fibroblasts were also studied. The Sr2+ ion loaded PEC-ALD/CS/PPy-NPs hydrogel showed no significant cytotoxicity towards human mesenchymal stem cells (MSCs) and fibroblasts. Sr2+ ions were electrochemically loaded and released from the electroactive hydrogels, and the application of an electrical stimulus enhanced the release of Sr2+ ions from gels by ca. 2-4 fold relative to the passive release control experiment. The antibacterial activity of Sr2+ ions against E. coli and S. aureus was demonstrated in vitro. Although these prototypical examples of Sr2+ loaded electroactive gels don't release sufficient Sr2+ ions to show antibacterial activity against E. coli and S. aureus, we believe future iterations with optimised physical properties of the gels will be capable of doing so.

Combination of Magnetic Lignocellulosic Particles, High-Density Polyethylene, and Carbon Black for the Construction of Composites with Tunable Functionalities

Biocomposites with unique functionalities for tailored applications are promising products for a sustainable future. In this work, a process concept of forming functional composites by combining of high-density polyethylene, carbon black, and magnetic lignocellulosic particles (wood flour) was demonstrated. The impacts of process parameters on morphologies, crystalline phase, and magnetic intensity of wood flour were identified. Magnetic, antistatic and mechanical properties of biocomposites were also evaluated. Lignocellulosic particles were encapsulated with magnetic nanoparticles, and the resulting composites exhibited tunable magnetic and antistatic properties. A noticeable feature is that magnetic nanoparticles were uniformly distributed in the matrices as a result of anchorage to lignocellulosic particles. Magnetic lignocellulosic particles and polymer resin had good compatibility. The resulting composites provided another opportunity for shielding materials, which could reduce the radiation in the living environment. These findings could provide a tunable strategy of the tailored use of lignocellulose-based composites in functional applications.

Surfactant-Triggered Fluorescence Turn "on/off" Behavior of a Polythiophene-graft-Polyampholyte

Polythiophene-graft-polyampholyte (PTP) is synthesized using N,N-dimethylaminoethyl methacrylate and tert-butyl methacrylate monomers by grafting from polythiophene backbone, followed by hydrolysis. The resulting polymer exhibits aqueous solubility via formation of small-sized miceller aggregates with hydrophobic polythiophene at the center and radiating polyionic side chains (cationic or anionic depending on the pH of the medium) at the outer periphery. The critical micelle concentration of PTP in acidic solution (0.025 mg/mL, pH = 2.7) is determined from fluorescence spectroscopy. PTP exhibits reversible fluorescence on and off response in both acidic and basic medium with the sequential addition of differently charged ionic surfactants, repeatedly. The fluorescence intensity of PTP at pH 2.7 increases with the addition of an anionic surfactant, sodium dodecyl benzenesulfonate (SDBS), due to the self-aggregation forming compound micelles. The fluorescence intensity of these solutions again decreases on addition of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), because of assembling of SDBS with CTAB, thus deassembling the PTP-SDBS aggregates. At pH 9.2, these turn on and turn off responses are also shown by PTP with the sequential addition of cationic surfactant (CTAB) and anionic surfactant (SDBS), respectively. This result shows that PTP has potential for surfactant-induced reversible fluorescence turn on and off using ionic surfactant (SDBS and CTAB) through self-assembling and deassembling of the ionic aggregates. The reversible aggregation and disaggregation process of PTP with the surfactants at both acidic and basic pH is supported from dynamic light scattering and Fourier transform infrared spectroscopy. The morphology of the above systems studied by transmission and scanning electron microscopy also supports the above aggregation and disaggregation process.

Structural and electrochemical studies of heterogeneous ion exchange membranes based on polyaniline-coated cation exchange resin particles

Polyaniline was deposited on polystyrene sulfonated divinyl benzene resin by varying polymerization time to fabricate heterogeneous PVC matrix membranes.

Multi-responsive behavior of highly water-soluble poly(3-hexylthiophene)-block-poly(phenyl isocyanide) block copolymers

Highly water-soluble block copolymers containing conjugated poly(3-hexylthiophene) and hydrophilic poly(phenyl isocyanide) segments were found to be responsive to multiple stimuli, such as temperature, pH and solvents.

Water soluble polythiophenes: preparation and applications

Different synthetic procedures for water soluble polythiophenes and their applications in sensing, detection of biomolecules and optoelectronic devices are discussed.

Morphing soft magnetic composites

Magnet filler-polymer matrix composites (Magpol) are an emerging class of morphing materials. Applications of Magpol can include artificial muscles, drug delivery, adaptive optics and self healing structures. Advantages of Magpol include remote contactless actuation, several actuation modes, high actuation strain and strain rate, self-sensing and quick response. The actuation modes of Magpol, its dynamic properties, work output and transduction characteristics are described. Analogies between Magpol actuation and phase transformations are presented. As an illustration of Magpol actuation, a proof of concept artificial muscle is presented. Current applications and future prospects are described.

Manufacturing and application of a fully polymeric electrophoresis chip with integrated polyaniline electrodes

This work describes the development of a fully polymeric microchip with integrated polymeric electrodes suitable for performing microchip electrophoresis. The polymer electrodes were fabricated in a thin film of the conducting polymer, polyaniline (PANI), by flash lithography using a studio camera flash and a transparency mask. During flash welding, exposed regions welded into non-conducting regions forming a conducting polymer circuit in the non-exposed regions. Using a structured layer of dry film photoresist for sealing, a polydimethylsiloxane (PDMS) substrate containing channels and reservoirs was bound to the PANI film to form an integrated microfluidic device. The conducting regions of the PANI film were shown to be capable of carrying the high voltages of up to 2000 V required for chip electrophoresis, and were stable for up to 30 minutes under these conditions. The PANI electrodes were used for the electrophoretic separation of three sugars labelled with 8-amino-1,3,6-pyrenetrisulfonic acid (APTS) in the dry film resist-PDMS hybrid device. Highly efficient separations comparable to those achieved in similar microchips using platinum electrodes confirm the potential of polyaniline as a new material suitable for high voltage electrodes in Lab-on-a-chip devices.

Improved thermoelectric behavior of nanotube-filled polymer composites with poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate)

The thermoelectric properties of carbon nanotube (CNT)-filled polymer composites can be enhanced by modifying junctions between CNTs using poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS), yielding high electrical conductivities (up to approximately 40000 S/m) without significantly altering thermopower (or Seebeck coefficient). This is because PEDOT:PSS particles are decorated on the surface of CNTs, electrically connecting junctions between CNTs. On the other hand, thermal transport remains comparable to typical polymeric materials due to the dissimilar bonding and vibrational spectra between CNT and PEDOT:PSS. This behavior is very different from that of typical semiconductors whose thermoelectric properties are strongly correlated. The decoupled thermoelectric properties, which is ideal for developing better thermoelectric materials, are believed to be due to thermally disconnected and electrically connected contact junctions between CNTs. Carrier transport at the junction is found to be strongly dependent on the type and concentration of stabilizers. The crucial role of stabilizers was revealed by characterizing transport characteristics of composites synthesized by electrically conducting PEDOT:PSS and insulating gum Arabic (GA) with 1:1-1:4 weight ratios of CNT to stabilizers. The influence of composite synthesis temperature and CNT-type and concentration on thermoelectric properties has also been studied. Single-walled (SW) CNT-filled composites dried at room temperature followed by 80 degrees C exhibited the best thermoelectric performance in this study. The highest thermoelectric figure of merit (ZT) in this study is estimated to be approximately 0.02 at room temperature, which is at least one order of magnitude higher than most polymers and higher than that of bulk Si. Further studies with various polymers and nanoparticles with high thermoelectric performance may result in economical, lightweight, and efficient polymer thermoelectric materials.

Fluorocarbon-Modified Organic Semiconductors: Molecular Architecture, Electronic, and Crystal Structure Tuning of Arene- versus Fluoroarene-Thiophene Oligomer Thin-Film Properties

We present here the systematic synthesis and comparative physicochemical characterization of a series of regiochemically varied and core size extension-modulated arene(perfluoroarene)-thiophene oligomers. The molecules investigated are: 5,5''-diphenyl-2,2':5',2'':5'',2'''-quaterthiophene (1), 5,5'-bis[1-[4-(thien-2-yl)phenyl]]-2,2'-dithiophene (2), 4,4'-bis[5-(2,2'-dithiophenyl)]-biphenyl (3), 5,5''-diperfluorophenyl-2,2':5',2'':5'',2'''-quaterthiophene (4), 5,5'-bis[1-[4-(thien-2-yl)perfluorophenyl]]-2,2'-dithiophene (5), 4,4'-bis[5-(2,2'-dithiophenyl)]-perfluorobiphenyl (6), 5,5''-diperfluorophenyl-2,2':5',2''-tertthiophene (7), 5,5'-diperfluorophenyl-2,2'-dihiophene (8), and 5,5-diperfluorophenylthiophene (9). Trends in optical absorption and emission parameters, molecular structures as defined by single-crystal X-ray diffraction, as well as electrochemical redox processes are described. The morphologies and microstructures of the vapor-deposited films grown over a range of growth temperatures have also been characterized. Field-effect transistor (FET) measurements demonstrate that all of these materials are FET-active and, depending on the molecular architecture, exhibit comparably good p- or n-type mobility when optimum film microstructural order is achieved. A very large n-channel mobility of approximately 0.5 cm2/Vs with I(on)/I(off) ratios > 10(8) is achieved for films of 4.

An EQCM Study of the Electropolymerization of Benzene in an Ionic Liquid and Ion Exchange Characteristics of the Resulting Polymer Film

The direct electropolymerization of benzene dissolved in the ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate was studied at room temperature applying the electrochemical quartz-crystal microbalance technique. Analysis of the damping changes showed that the Sauerbrey equation could be applied for data evaluation. In the polymer, every third to fourth benzene ring carried a positive charge in the oxidized state. During electropolymerization, some ionic liquid was absorbed in the growing polymer. The redox behavior was characterized by wide peaks typical for conducting polymers. Charge neutrality of the polymer during redox cycling was maintained by anion and cation exchange with the ionic liquid. With increasing scan rate, cation exchange became more and more important.

Building Blocks for N-Type Molecular and Polymeric Electronics. Perfluoroalkyl- versus Alkyl-Functionalized Oligothiophenes (nTs; n = 2−6). Systematic Synthesis, Spectroscopy, Electrochemistry, and Solid-State Organization

The synthesis, comparative physicochemical properties, and solid-state structures of five oligothiophene (nT) series differing in substituent nature and attachment, regiochemistry, and oligothiophene core length (n) are described. These five series include the following 25 compounds: (i) alpha,omega-diperfluorohexyl-nTs 1 (DFH-nTs, n = 2-6), (ii) beta,beta'-diperfluorohexyl-nTs 2 (isoDFH-nTs, n = 2-6), (iii) alpha,omega-dihexyl-nTs 3 (DH-nTs, n = 2-6), (iv) beta,beta'-dihexyl-nTs 4 (isoDH-nTs, n = 2-6), and (v) unsubstituted oligothiophenes 5 (alphanTs, n = 2-6). All new compounds were characterized by elemental analysis, mass spectrometry, and multinuclear NMR spectroscopy. To probe and address quantitatively how the chemistry and regiochemistry of conjugated core substitution affects molecular and solid-state properties, the entire 1-5 series was investigated by differential scanning calorimetry, thermogravimetric analysis, and optical absorption and emission spectroscopies. Single-crystal X-ray diffraction data for several fluorocarbon-substituted oligomers are also presented and compared. The combined analysis of these data indicates that fluorocarbon-substituted nT molecules strongly interact in the condensed state, with unit cell level phase separation between the aromatic core and fluorocarbon chains. Surprisingly, despite these strong intermolecular interactions, high solid-state fluorescence efficiencies are exhibited by the fluorinated derivatives. Insight into the solution molecular geometries and conformational behavior are obtained from analysis of optical and variable-temperature NMR spectra. Finally, cyclic voltammetry data offer a reliable picture of frontier MO energies, which, in combination with DFT computations, provide key information on relationships between oligothiophene substituent effects and electronic response properties.

Analysis of polyaniline oligomers by laser desorption ionization and solventless MALDI

While direct laser desorption ionization of soluble polyaniline dried onto metal sample plates results in mass spectra that are similar to previously shown electrospray ionization data of similar samples, laser desorption of unsolubilized solid polyaniline results in major fragmentation of the phenyl rings. Solventless MALDI, a recently developed technique for insoluble or slightly soluble species, involves the use of only solid analyte and matrix during sample preparation. Solventless MALDI of solid polyaniline results in mass spectra that are similar to the direct laser desorption ionization spectra of the soluble oligomers with some larger molecular weight oligomers also being detected. Based on the matrix used, different series of polyaniline with dissimilar end groups are detected. The matrix also affects the percentages of benzenoid and quinoid units in the oligomers. Thus, solventless MALDI appears to be a promising new technique for the mass spectrometric analysis of low solubility, but industrially important, polyanilines.