Water Soluble Photo- and Electroluminescent Alkoxy-Sulfonated Poly(p-phenylenes) Synthesized via Palladium Catalysis

Correlating Molar Mass, π-Conjugation, and Optical Properties of Narrowly Distributed Anionic Polythiophenes in Aqueous Solutions

Polythiophene-based conjugated polyelectrolytes (CPE) are attracting increasing attention as sensor or interface materials in chemistry and biology. While cationic polythiophenes are better understood, limited structural information is available on their anionic counterparts. Limited access to well-defined polymers has made the study of structure-property relationships difficult and clear correlations have remained elusive. By combining controlled Kumada catalyst transfer polymerization with a polymer-analog substitution, regioregular and narrowly distributed poly(6-(thiophen-3-yl)hexane-1-sulfonate)s (PTHS) with tailored chain length are prepared. Analysis of their aqueous solution structures by small-angle neutron scattering (SANS) revealed a cylindrical conformation for all polymers tested, with a length close to the contour length of the polymer chains, while the estimated radii remain too small (<1.5 nm) for extensive π-stacking of the chains. The latter is particularly interesting as the longest polymer exhibits a concentration-independent structured absorption typical of crystalline polythiophenes. Increasing the ionic strength of the solution diminishes these features as the Coulomb repulsion between the charged repeat units is shielded, allowing the polymer to adopt a more coiled conformation. The extended π-conjugation, therefore, appears to be a key parameter for these unique optical features, which are not present in the corresponding cationic polythiophenes.

Polyelectrolyte-Dye Interactions: An Overview

Polyelectrolytes are polymers with repeating units of ionizable groups coupled with counterions. Recently, polyelectrolytes have drawn significant attention as highly promising macromolecular materials with potential for applications in almost every sector of our daily lives. Dyes are another class of chemical compounds that can interact with substrates and subsequently impart color through the selective absorption of electromagnetic radiation in the visible range. This overview begins with an introduction to polyelectrolytes and dyes with their respective definitions, classifications (based on origin, molecular architecture, etc.), and applications in diverse fields. Thereafter, it explores the different possible interactions between polyelectrolytes and dyes, which is the main focus of this study. The various mechanisms involved in dye-polyelectrolyte interactions and the factors that influence them are also surveyed. Finally, these discussions are summarized, and their future perspectives are presented.

Thermal and Spectral Analysis of Novel Amide-Tethered Polymers from Poly(allylamine)

Post-polymerization modification of poly(allylamine hydrochloride) was applied to synthesize a library of amide-linked polyelectrolytes with tethered aliphatic, aromatic, and cubyl moieties. The efficacy of amidation was determined to be between 12 and 98 %, depending on the electronics, sterics, and solubility of the amide linkage. 13C solid-state NMR was used to further validate their structure. Thermogravimetric analysis and differential scanning calorimetry analysis indicated that none of the new polymers displayed a classic melt/freeze profile, but all displayed onset decomposition temperatures smaller than 215°C. We anticipate that the structure–property relationships observed in the resulting library of graft-modified polymers can facilitate better understanding of how to design polyelectrolytes for the construction of well-defined multilayer systems.

Pyridine-based poly(aryleneethynylene)s: a study on anionic side chain density and their influence on optical properties and metallochromicity

We report the Pd-catalyzed synthesis of six new water soluble, alternating poly(p-phenylene-ethynylene-p-pyridinylene-ethynylene) (abcb-alternating) copolymers and one poly(p-pyridinyleneethynylene).

Aggregation-deaggregation-triggered, tunable fluorescence of an assay ensemble composed of anionic conjugated polymer and polypeptides by enzymatic catalysis of trypsin

We prepared a water-soluble conjugated polymer composed of electron-donating units and electron-accepting groups in the backbone. The polymer exhibits a short wavelength (blue) emission in aqueous solution and long wavelength (red) emission in the solid state, because of intermolecular energy transfer. Considering this, we develop a new approach for the sensitive detection of trypsin, which is known to control pancreatic exocrine function, using an ensemble system composed of the anionically charged conjugated polymer and cationically charged polypeptides (such as polylysine and polyarginine). The blue-emitting, water-soluble conjugated polymer becomes aggregated upon exposure to the polypeptides, leading to a red-emitting assay ensemble. The red-emitting assay ensemble becomes dissociated in the conjugated polymer and polypeptide fragments by selective degradation of trypsin, which then exhibits recovery of blue emission. This emission-tuning assay ensemble allows for detection of trypsin at nanomolar concentrations, which enables naked-eye detection. Importantly, this strategy can be employed for label-free, continuous assay for trypsin.

The detection of thrombin using a mixture of a fluorescent conjugated polyelectrolyte and fibrinogen and implementation of a logic gate

A highly sensitive and selective detection of thrombin is accomplished using an emission color-tunable conjugated polyelectrolyte. An implementation of a combined logic gate was realized upon emission modulation of the system including the polymer, fibrinogen, thrombin, and heparin.

Highly selective ensembles for D-fructose based on fluorescent method in aqueous solution

Three highly sensitive and selective switches for monosaccharides were composed by anionic polyelectrolyte PPPSO(3)Na and cationic viologen quencheres BBVs. The sensing processes of three ensembles (PPPSO(3)Na/o-BBV, PPPSO(3)Na/m-BBV and PPPSO(3)Na/p-BBV) to common seven monosaccharides have been determined by fluorescence spectra at pH 7.4 buffer solution. The results show that the three sensing ensembles all embody higher selectivity and sensitivity for d-fructose with reversible "on-off-on" fluorescence response. The research results can provide a new mode for developing highly selective probes.

Highly selective cysteine detection and bioimaging in zebrafish through emission color change of water-soluble conjugated polymer-based assay complex

A new concept for rapid, label-free cysteine sensing method is proposed via possible naked eye-detection of red-to-blue emission color change. Intermolecular exciton migration in conjugated polyelectrolyte-based assay complex is adopted to enhance selectivity and sensitivity for cysteine sensing by formation and dissociation of polymer-Hg(2+)-thymine assay complex in the absence and presence of cysteine, respectively. The assay complex shows red emission due to cooperative aggregation of conjugated polyelectrolyte, thymine, and Hg(2+). Upon exposure to cysteine, the assay complex dissociates into individual molecules showing transparent, blue-emitting solution, because cysteine extracts Hg(2+) from the assay complex via more favorable binding between cysteine and Hg(2+).

Anionic poly(p-phenylenevinylene)/layered double hydroxide ordered ultrathin films with multiple quantum well structure: a combined experimental and theoretical study

The sulfonated phenylenevinylene polyanion derivate (APPV) and exfoliated Mg-Al-layered double hydroxide (LDH) monolayers were alternatively assembled into ordered ultrathin films (UTFs) employing a layer-by-layer method, which shows uniform yellow luminescence. UV-vis absorption and fluorescence spectroscopy present a stepwise and regular growth of the UTFs upon increasing deposited cycles. X-ray diffraction, atomic force microscopy, and scanning electron microscopy demonstrate that the UTFs are orderly periodical layered structure with a thickness of 3.3-3.5 nm per bilayer. The APPV/LDH UTFs exhibit well-defined polarized photoemission characteristic with the maximum luminescence anisotropy of approximately 0.3. Moreover, the UTF exhibit longer fluorescence lifetime (3-3.85-fold) and higher photostability than the drop-casting APPV film under UV irradiation, suggesting that the existence of a LDH monolayer enhances the optical performance of the APPV polyanion. A combination study of electrochemistry and periodic density functional theory was used to investigate the electronic structure of the APPV/LDH system, illustrating that the APPV/LDH UTF is a kind of organic-inorganic hybrid multiple quantum well (MQW) structure with a low band energy of 1.7-1.8 eV, where the valence electrons of APPV can be confined into the energy wells formed by the LDH monolayers effectively. Therefore, this work not only gives a feasible method for fabricating a luminescence ultrathin film but also provides a detailed understanding of the geometric and electronic structures of photoactive polyanions confined between the LDH monolayers.

Conjugated polyelectrolytes: synthesis, photophysics, and applications

Organic optoelectronic polymers have evolved to the point where fine structural control of the conjugated main chain, coupled with solubilizing and property-modifying pendant substituents, provides an entirely new class of materials. Conjugated polyelectrolytes (CPEs) provide a unique set of properties, including water solubility and processability, main-chain-controlled exciton and charge transport, variable band gap light absorption and fluorescence, ionic interactions, and aggregation phenomena. These characteristics allow these materials to be considered for use in applications ranging from light-emitting diodes and electrochromic color-changing displays, to photovoltaic devices and photodetectors, along with chemical and biological sensors. This Review describes the evolution of CPE structures from simple polymers to complex materials, describes numerous photophysical aspects, including amplified quenching in macromolecules and aggregates, and illustrates how the physical and electronic properties lead to useful applications in devices.

Design of Cationic Conjugated Polyelectrolytes for DNA Concentration Determination

Cationic conjugated polyelectrolytes poly110 and poly120 were designed, synthesized, and characterized with the anticipation of function in the determination of double-stranded DNA concentration [dsDNA]. Their structures contain a pi-delocalized optically active backbone composed of phenylene-fluorene segments copolymerized with 2,1,3-benzothiadiazole (BT) units and charged pendant groups that allow excellent solubility in water. The subscript in poly1x refers to the molar percent of BT units in the chain. Addition of dsDNA to poly110 or poly120 results in a change in the color of emission from blue to green. These spectral changes can be treated to obtain the parameter delta, which can be used to generate calibration curves that indicate [dsDNA]. Analysis of photoluminescence spectra reveals that dsDNA addition gives rise to more efficient FRET from blue emitting segments to the BT sites, an increase in the BT emission quantum yield, and partial quenching of the phenylene-fluorene segments. Studies were also carried out to maximize the range of [dsDNA] determination. We find that by combining the response from two different initial concentrations of poly110, it is possible to generate calibration curves that respond with a difference in [dsDNA] of over 7 orders of magnitude.

Electrochemically enabled polyelectrolyte multilayer devices: from fuel cells to sensors

With an ever-increasing need for thin, flexible and functional materials in electrochemical systems, the layer-by-layer (LbL) technique provides a simple and affordable route in creating new, active electrodes and electrolytes. The LbL technique, which is based upon the alternate adsorption of oppositely charged species from aqueous solution, possesses unprecedented control of materials selection ( polyelectrolytes, clays, nanoparticles, proteins), materials properties ( conductivity, glass-transition temperature) and architecture ( blends, stratified-layers, pores). These advantages make LbL assemblies excellent candidates for use in proton-exchange membrane and direct methanol fuel-cells, batteries, electrochromic devices, solar cells, and sensors. This review addresses the design of LbL films for electrochemical systems and recent progress.

Cationic Dithieno[3,2-b:2‘,3‘-d]phospholes: A New Building Block for Luminescent, Conjugated Polyelectrolytes

Cationic dithieno[3,2-b:2',3'-d]phospholes are accessible very efficiently by methylation of the phosphorus center. Further functionalization with bromo substituents in 2,6-positions affords a polymerizable monomer that can be copolymerized with a difunctionalized fluorene in a Suzuki-Miyaura-type cross-coupling protocol. The monomers as well as the resulting conjugated polyelectrolyte based on the phospholium units show very intriguing photoluminescence properties, even in the solid state. [structure: see text]