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This report demonstrates the synthesis of a trihybrid system (PBI-NP-GO) consisting of perylene bisimide appended peptide (PBI-UW) nanofibers, silver nanoparticles (PBI-AgNP), and graphene oxide (GO) nanosheet. Tryptophan-containing PBI molecules in an aqueous medium can reduce silver ions into silver nanoparticles in the presence of sunlight to form a dihybrid system consisting of nanofibers and nanoparticles; the addition of GO into the dihybrid system ultimately leads to the formation of the trihybrid system. The trihybrid system was thoroughly characterized by various spectroscopic and microscopic techniques, such as ultraviolet-visible (UV-vis), Fourier transform-infrared (FT-IR), X-ray photoelectron spectroscopy (XPS), RAMAN, and field emission transmission electron microscopy (FEG-TEM). The so-formed trihybrid system was successfully utilized as a potential photocatalyst for the reduction of carcinogenic Cr(VI) to non-toxic Cr(III) under irradiation with blue LED light. An almost complete reduction of Cr(VI) was achieved within 30 minutes of irradiation. Moreover, good photo-switching behaviour was observed with the highest photocurrent gain of 5.11 (Ion/Ioff) compared to PBI-AgNP (dihybrid) and PBI-UW, where Ion/Ioff values of 3.92 and 2.31, respectively, were obtained. The photocatalytic activity and photo-switching behaviour of the trihybrid system are due to efficient photo-induced charge separation. [ABSTRACT FROM AUTHOR]

Electroactive polymers (EAPs) have the interesting property of generation and flow of charges and possess exciting tunable optoelectronic properties by incorporating side chains via 'grafting' from the backbone chain retaining its properties and importing new properties from the grafted chains. The graft copolymers of EAPs exhibit exciting tunable optoelectronic properties by varying external stimuli like pH, temperature, ions, surfactants, light etc. Grafting of two main electroactive polymers e.g. polythiophene (PT) and poly(vinylidene fluoride) (PVDF) have spurred significant research attention and the controlled grafting has been made using atom transfer radical polymerization (ATRP) technique with suitable catalyst/ligand systems. Few examples of grafting of PT and PVDF by RAFT polymerization are also described. This feature article delineates controlled grafting of different stimuli-responsive polymers on polythiophene and PVDF backbone highlighting their optoelectronic properties, useful for making chemical/biological sensors, logic gates and antifouling/antibacterial membranes. Interactions of the grafted chains with the external physical or chemical stimuli (like pH, temperature, photoirradiation, ions, surfactants, etc.) significantly alter the backbone conformation both in solution and solid state. This leads to changes in conjugation length of the backbone chain, hence tunes the band gap varying the optoelectronic properties useful for fabrication of stimuli dependent sensors and modulation of membrane pore size suitable for antifouling and antibacterial membranes. [ABSTRACT FROM AUTHOR]

A water-soluble polymer–peptide conjugate, composed of poly(thiophene methacrylate) (PTMA) and cationic peptide appended perylene diimide (PBI-NH3+), was fabricated. The dipolar interaction between PTMA and PBI-NH3+ helped to uncoil the polythiophene backbone, resulting in an increase of the conjugation length, which was thoroughly studied by UV-Vis, Fourier transform infrared (FTIR), and X-ray diffraction (XRD) spectra. The morphology of PTMA changes from vesicular to a highly entangled fibrillar network in the hybrid as evident from the HR-TEM study. Fluorescence spectroscopic study and time-correlated single-photon counting (TCSPC) studies were made to understand the effect of interaction on the photoluminescence (PL) properties of the hybrid. The current–voltage (I–V) plots of hybrid materials showed synergistic enhancement of current with voltage, showing an interesting organic mixed ionic and electronic conductivity (OMIEC) property, which was further supported through current–time (I–t) and Nyquist plot results. This conjugate material shows an enhancement of photo-switching behaviour with the highest photocurrent gain of 9. 8 (Ion/Ioff) for the composite with 27 wt% PBI-NH3+. The increase in photoswitching property is attributed to efficient charge (electron–hole) separation and holds a future promise for fabricating new types of macromolecular OMIEC systems along with excellent photocurrent switching efficiency. [ABSTRACT FROM AUTHOR]

Silver/polyaniline-dinonylnaphthalene disulfonic acid (PANI-DNNDSA) gel nanocomposites are prepared from the reduction of silver salt by polyaniline in formic acid medium. Scanning electron micrographs (SEM) indicate the presence of three-dimensional fibrillar network structure and the silver nanoparticles remain dispersed within the PANI-DNNDSA fibrillar network. Differential scanning calorimetric (DSC) study shows reversible first-order phase transition characterizing the composite to behave as a thermoreversible gel. Transmission electron micrographs (TEM) show a decrease of nanoparticle size with increasing Ag[NO.sub.3] concentration. Wide angle X-ray scattering (WAXS) patterns show lamellar structure in the gel as well as in the gel metal nanocomposites (GMNCs) and the two melting peaks in the DSC patterns correspond to the melting of monolayer and bilayer crystals produced from the interdigitation of DNNDSA tails anchored from PANI chains within the PANI lamella. The above melting points are greater in the GMNCs than that of pure gel indicating the formation of complex melting thermogram with crystallites produced from the anchored surfactants tails at the surface of Ag nanoparticles. The GMNCs show a higher thermal stability than that of pure PANI-DNNDSA gel. PANI-DNNDSA gel has an emission peak at 354 nm but fluorescence quenching occurs in the GMNCs and the emission peak becomes red shifted. Also in the UV-vis spectra the π band-polaron band transition peak shows a red shift and the DC conductivity increases with increasing Ag nanoparticle concentration in the GMNCs. The current (I)-voltage (V) characteristic curves indicate Ohmic nature of conductivity of the gel and the current at the same voltage increases appreciably with increasing Ag nanoparticle concentration. These GMNCs are easily processible due to its thermoreversible nature. So, an easily processible, thermally stable and highly conducting DNNDSA-doped PANI-Ag gel nanocomposite with interesting photoluminescent property has been successfully developed suitable for optoelectronic applications. POLYM. ENG. SCI., 50:446-454, 2010. [C]2009 Society of Plastics Engineers, INTRODUCTION Polyaniline (PANI) is an important conducting polymer for its high conductivity (1), unique redox properties (2), easier method of synthesis (3), and good environmental stability (4), (5). Because of [...]

Poly(3-hexyl thiophene) (P3HT) organically modified montmorillonite (om-MMT) polymer nanocomposites (PNCs) are prepared in the melt-cooled state. The hierarchical structures up to third order, namely, side chain mesomorph formation followed by the interchain lamellar structure of P3HT and finally its intercalation within the clay is observed.

Poly(3-dodecyl thiophene) (P3DDT) produces thermoreversible gels in 0-, m-, and p-xylene (Xy). From the thermodynamic study, it is concluded that during gelation of P3DDT-p-xylene systems polymer-solvent complexes are produced.