Conducting polymer-based electro-responsive smart suspensions

Electrorheological Fluids Based on Porous Carboxyl-Functionalized Polytriphenylamines

Electrorheological fluids (ER) make up a class of smart materials that are distinguished by their capacity to alter their rheological characteristics in a controlled and reversible manner in response to an externally applied electric field (E). As an inherent polarizable anhydrous ER-active material, polyaniline (PAni)-based materials are among the most frequently utilized ER-active materials. However, PAni can only be used as an ER-active material after carefully adjusting its conductivity to an appropriate range. Three-dimensional (3D) conjugated microporous polymer (CMP) analogs of PAni have a nitrogen-rich porous and hierarchical structure, low density, and appropriate conductivity that can be used to explore ER performance and dispersion stability. In this study, a carboxylic acid functionalized version with a greater polar porous surface was designed to obtain higher polarizability and appropriate conductivity without the need for any dedoping process and thus enhanced ER performance. For this purpose, polytriphenylamine (PTPA) and an extended carboxylic-acid-functionalized PTPA (PTPA-COOH) were synthesized as ER-active materials by Buchwald-Hartwig cross-coupling. The structural, morphological, electrical, microstructural, and surface properties were investigated in detail before the ER performance was determined. Dispersions of the CMPs were prepared in silicon oil and examined under different E values by measuring shear stress, shear viscosity, and moduli values. PTPA-COOH dispersion with 10 wt % concentration exhibited excellent dispersion stability of 99% and enhanced ER performance, including high shear stress (static yield stress of 370 Pa at 3.5 kV/mm), repeatable and reversible electric field response, and obvious dielectric loss peak (relaxation time of 0.01 s). This class of functionalized 3D analogs of PAni shows significant promise as ER-active materials for applications in smart fluids.

Preparation of graft copolymer of chitosan-poly ortho-toluidine for antibacterial properties

The combination polymers or copolymers have new and combined properties and increase the efficiency of the new polymer. Biopolymers are biodegradable and can play the role of biocompatible and biodegradable in composite polymers. Therefore, poly ortho-toluidine was grafted on chitosan (Cs-g-POT) by chemical and electrochemical polymerization methods. Cs-g-POT was characterized by FTIR, UV-visible, and 1H NMR spectroscopy techniques. The thermal behaviors of the copolymer were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The images of the surface of the copolymer obtained from imaging SEM confirm the successful attachment of POT on chitosan and indicate that the graft polymerization has been successfully performed with both methods. The percentage and efficiency of engraftment were carefully measured and reported. The electrical conductivity of Cs-g-POT was measured by the four-point method and the conductivity was 9.1 × 10-4 S/cm. The copolymer's antibacterial property was studied on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa as a common bacterium in skin wounds. These studies were investigated using the disk diffusion and minimum inhibitory concentration (MIC) methods. In all tested concentrations the polymer could inhibit the growth of E. coli and P. aeruginosa significantly. However, it inhibited the growth of S. aureus in concentrations above 1 μg. Bacteria are adsorbed on the surface of the polymer by polar-polar and Van Der Waals interactions, where they undergo cell lysis by dopant and electron transfer, and eventually bacterial cell death. Due to its scaffolding properties, this polymer will have a very good use in tissue and bone repair as well as anti-cancer drugs.

Synthesis and Impedance Spectroscopy of Poly(p-phenylenediamine)/Montmorillonite Composites

Poly(p-phenylenediamine)/montmorillonite (PPDA/MMT) composites were prepared by the oxidative polymerization of monomers intercalated within the MMT gallery, using ammonium peroxydisulfate as an oxidant. The intercalation process was evidenced by X-ray powder diffraction. The FT-IR and Raman spectroscopies revealed that, depending on the initial ratio between monomers and MMT in the polymerization mixture, the polymer or mainly oligomers are created during polymerization. The DC conductivity of composites was found to be higher than the conductivity of pristine polymer, reaching the highest value of 10^-6 S cm^-1 for the optimal MMT amount used during polymerization. Impedance spectroscopy was performed over wide frequency and temperature ranges to study the charge transport mechanism. The data analyzed in the framework of conductivity formalism suggest different conduction mechanisms for high and low temperature regions.