Anionic Spherical Polyelectrolyte Brushes Research Articles

Application of spherical polyelectrolyte brushes microparticle system in flocculation and retention.

In this paper, a microparticle system consisting of cationic polyacrylamide (CPAM) and anionic spherical polyelectrolyte brushes (ASPB) is proposed to improve the retention of pulp suspension containing bleached reed kraft pulp and precipitated calcium carbonate (PCC). We first describe the preparation of ASPB. The ASPB, consisting of a carbon sphere (CS) core and a shell of sodium polystyrene sulfonate (PSSNa) brushes, was synthesized by surface-initiated polymerization. The structure and morphology of ASPB were characterized by Fourier-transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Then, flocculation and retention of pulp suspension by a CPAM/ASPB dual-component system were examined. Our results indicate that more highly effective flocculation and higher retention efficiency could be achieved simultaneously by a CPAM/ASPB dual-component system when compared to the conventional microparticle system. Bridging flocculation and electrostatic attraction might be the main flocculation mechanism for CPAM/ASPB systems.

Controllable immobilization of proteins in quenched spherical polyelectrolyte brushes as observed by fluorescence spectroscopy and small angle X‐ray scattering

ABSTRACTThe immobilization of lysozymes (pI = 11) onto anionic spherical polyelectrolyte brushes (SPB) which consist of a solid polystyrene core and a densely grafted poly(styrene sulfonate) (PSS) shell was systematically studied by fluorescence spectroscopy and small angle X‐ray scattering. Results show that the capture of lysozyme by PSS brush is a dynamic process, which involves a quick agglomeration stage and a slow rearrangement one. And lysozyme inclines to immobilize in the inner layer of the brush, and saturation of lysozyme adsorption onto the SPB is gradually reached as the protein concentration increases, proceeding from the inside to the outside of the brush layers. As increasing the pH and ionic strength, the lysozyme previously adsorbed will be partially released and migrate from the inner to the outer layer of SPB. Last competitive adsorption tests between lysozyme and BSA or β‐glucosidase were performed, indicating that besides electrostatic interaction counterion release force also plays an important role in protein adsorption. SPB was proved to be ideal candidate for controllable immobilization of protein, which can be extended into various applications, such as drug delivery and protein separation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 1577–1588

Dielectric analysis based on spherical-shell model for cationic and anionic spherical polyelectrolyte brushes

We report here a dielectric study on cationic and anionic spherical polyelectrolyte brush (SPB) (consisting of a polystyrene (PS) core and poly (2-aminoethylmethacrylate hydrochloride (PAEMH) chains or poly (acrylic acid) (PAA) chains grafted onto the core) suspensions over a frequency range of 40 Hz–110 MHz. The relaxation behavior of the suspensions shows significant changes in the brush layer properties when changing the particle mass fraction or pH of the system. After eliminating the electrode polarization effect at a low frequency, two definite relaxations related to interfacial polarization, around 100 kHz and 10 MHz respectively, are observed. Based on a single layer spherical-shell model, we developed a curve-fitting procedure to analyze such dielectric spectra for soft particles, and then calculated the dielectric properties of the components of the SPBs (such as the permittivities and conductivities of the layer and solution phase), especially the layer thickness ds of the polyelectrolyte chain (PE) layer. We also found a larger confinement degree of counterions in the PAEMH brush due to the protonation of the amino group. Moreover, the repulsive force between the SPB particles is evaluated by using the ds combined with the relative theoretical formulas. We conclude that by raising (reducing) the acidity of the system, the stability of the PAEMH-SPB (PAA-SPB) suspension was improved. An increase in particle concentration can also improve the stability of these two dispersions.

Spherical Polyelectrolyte Brushes as a Novel Platform for Paramagnetic Relaxation Enhancement and Passive Tumor Targeting.

A novel platform for the development of highly efficient magnetic resonance imaging (MRI) contrast agents has been demonstrated. New contrast agents are designed and produced through electrostatic self-assembly of cationic gadolinium(III) complexes onto anionic spherical polyelectrolyte brushes (SPB). The structurally well-defined SPB are composed of polystyrene core and polyacrylic acid brush layer, where numerous binding sites and confined microenvironments are available for the embedment of the gadolinium(III) contrast agents. Both in vitro and in vivo experiments show excellent biocompatibility and relaxometric performance of these SPB-based gadolinium hybrid materials. The enhanced relaxivity value is up to 86.2 mM-1 s-1 per Gd, a remarkably high record value at 1.5 T magnetic field. In vivo imaging displays a prolonged blood circulation time and massive accumulation of the contrast agents at the tumor region due to the enhanced permeability and retention effect. The SPB-based gadolinium hybrid materials not only broaden the horizons of new MRI contrast agents, but also have a great potential for tumor diagnosis.

Polyaniline-Doped Spherical Polyelectrolyte Brush Nanocomposites with Enhanced Electrical Conductivity, Thermal Stability, and Solubility Property

The synthesis procedure and dopant are crucial to the electrical conductivity, thermal stability, and solubility properties of polyaniline (PANI). In this paper, high-performance PANI was synthesized by means of chemical oxidative polymerization using anionic spherical polyelectrolyte brushes (ASPB) as dopant. The bonding structure, crystallographic structure, morphology, and thermal stability of the conductive nanocomposite were analyzed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA) respectively. Meanwhile, investigation on the electrical conductivity suggested that the room-temperature electrical conductivity of PANI doped with ASPB (PANI/ASPB) was 19.3 S/cm, which was higher than that of PANI (7.0 S/cm), PANI doped with poly(sodium-p-styrenesulfonate) (PSS) (PANI/PSS) (14.6 S/cm), PANI doped with SiO2 (PANI/SiO2) (18.2 S/cm), and PANI doped with canonic spherical polyelectrolyte brushes (CSPB) (PANI/CSPB) (8.0 S/cm). Meanwhile, the addition of ASPB improved the thermal stability and solubility properties of PANI. ASPB played the role of template. Conductive mechanism of PANI/ASPB nanocomposite can be explained by the theoretical models of three-dimensional variable range-hopping (3D VRH).

An anionic spherical polyelectrolyte brushes-driven approach to synthesize conductive composites

The composites of anionic spherical polyelectrolyte brushes/conducing polymer (ASPB/CP) have been successfully prepared by chemical oxidative polymerization of aniline and pyrrole monomers in an acidic medium containing anionic spherical polyelectrolyte brushes. These composites were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectrometry, zeta potentials, X-ray photoelectron spectroscopy, and four probe methods. It was found that the poly(aniline-co-pyrrole) was uniformly coated on the surface of ASPB. Besides, the ASPB/CP composites had higher doping level than the pure copolymer after doping with ASPB. Moreover, these composites also showed better solubility and storage stability than pure copolymer. The electrical conductivity of the ASPB/CP composites at room temperature was 7.2 S/cm, while it was 2.4 S/cm for the pure copolymer under the same circumstances.

Improving Electrical Conductivity, Thermal Stability, and Solubility of Polyaniline-Polypyrrole Nanocomposite by Doping with Anionic Spherical Polyelectrolyte Brushes.

The extent to which anionic spherical polyelectrolyte brushes (ASPB) as dopant improved the performance of polyaniline-polypyrrole (PANI-PPy) nanocomposite was investigated. Different characterization and analytical methods including Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) confirmed that ASPB serving as dopant could improve the comprehensive properties of PANI-PPy nanocomposite. It was different from dopants such as SiO2, poly(sodium-p-styrenesulfonate) (PSS), and canonic spherical polyelectrolyte brushes (CSPB) which only enhanced the performance of PANI-PPy nanocomposite on one or two sides. The electrical conductivity of (PANI-PPy)/ASPB nanocomposite at room temperature was 8.3 S/cm, which was higher than that of PANI-PPy (2.1 S/cm), (PANI-PPy)/PSS (6.8 S/cm), (PANI-PPy)/SiO2 (7.2 S/cm), and (PANI-PPy)/CSPB (2.2 S/cm). Meanwhile, (PANI-PPy)/ASPB nanocomposite possessed enhanced thermal stability and good solubility. In addition, the effects of polymerization temperature, the molecular weight of grafted polyelectrolyte brushes, and storage time on electrical conductivity were discussed.

Tunable immobilization of protein in anionic spherical polyelectrolyte brushes as observed by small-angle X-ray scattering

Tunable immobilization of bovine serum albumins (BSA) onto anionic spherical polyelectrolyte brushes (SPB) by changing BSA concentration, pH, and ionic strength was mainly observed by small-angle X-ray scattering (SAXS). Change of the BSA amount immobilized in SPB can be determined by SAXS which was confirmed by UV spectroscopy, and SAXS is the unique method to “see” the distribution of BSA in SPB. More BSA entered into brush layer upon increasing the protein concentration or decreasing the ionic strength of solutions. When pH increased from 3 to 5 (around the isoelectric point of BSA 4.9), more BSA came into the brush inner layer, while the proteins partly moved to the outer layer when pH continued to increase. After pH was higher than 7, most of BSA were desorbed from SPB. SAXS is proved to be a powerful tool to monitor the tunable immobilization and distribution of proteins in SPB.

Preparation and properties of polyaniline–anionic spherical polyelectrolyte brushes nanocomposite

A novel polyaniline–anionic spherical polyelectrolyte brushes (PANI/ASPB) nanocomposite was synthesised by means of chemical oxidative polymerisation. Different characterisation and analytical methods involving scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction and thermo-gravimetric analysis confirmed that anionic spherical polyelectrolyte brushes served both as a dopant and as a template. While polyaniline (PANI) nanocomposites have a ‘rod-like’ or fibrillar morphology, the PANI/ASPB nanocomposite displayed a sphere-like structure. The room temperature electrical conductivity of the PANI/ASPB nanocomposite was 26.3 S/cm, which is higher than that of PANI (7.1 S/cm). In addition, PANI/ASPB nanocomposites possessed enhanced thermal stability and good solubility properties.

Synthesis and Characterization of Polyaniline Dopd with Anionic Spherical Polyelectrolyte Brushes

The synthesis of polyaniline (PANI) doped with anionic spherical polyelectrolyte brushes (ASPB) (PANI/ASPB nanocomposite) by means of in situ chemical oxidative polymerization were presented. The PANI/ASPB nanocomposite was characterized by Fourier trans-form infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), Energy dispersive x-ray detector (EDX), and Thermo-gravimetric analysis (TGA). Results showed that PANI/ASPB nanocomposite was successfully fabricated with regular morphology. Investigation of the electrical conductivity at room temperature showed that the electrical conductivity of PANI/ASPB nanocomposite was 9.03 S/cm, which was higher than that of PANI (2.7 S/cm). The measurement of dispersity demonstrated that PANI/ASPB nanocomposite had enhanced dispersity in water.

Controllable synthesis and characterization of poly(aniline‐co‐pyrrole) using anionic spherical polyelectrolyte brushes as dopant and template

A poly(aniline‐co‐pyrrole), using anionic spherical polyelectrolyte brushes (ASPB) as dopant and template, was synthesized by chemical oxidation polymerization. The composites were characterized by scanning electron microscopy (SEM), Fourier‐transform infrared spectrometry (FTIR), X‐ray diffraction (XRD), and electrical studies. The SEM images confirmed that the composites had a spherical‐like structure, with a size of ca. 170 nm. The FTIR spectra showed the intermolecular interaction between poly(aniline‐co‐pyrrole) and ASPB. The XRD analysis revealed that the interplanar distance of the copolymers increased from 0.373 nm to 0.391 nm. The electrical conductivity of the poly(aniline‐co‐pyrrole)/ASPB nanocomposites at room temperature was 8.3 S cm−1, higher than that of the conducting copolymers (2.1 S cm−1). These conductive nanocomposites have nanoparticle size, controllable morphology, and the potential for application in inkjet electronic printing. POLYM. COMPOS., 35:1858–1863, 2014. © 2014 Society of Plastics Engineers

Synthesis and characterization of poly(sodium-p-styrenesulfonate)/modified SiO2 spherical brushes

The multistep procedures for preparing novel anionic spherical polyelectrolyte brushes (ASPB) by grafting sodium-p-styrenesulfonate (SSS) from the surface of !-methacryloxypropyl trimethoxy-silane modified SiO2 nanoparticles were demonstrated. The morphology of ASPB was characterized by Transmission Electron Microscopy (TEM) and Scan- ning Electron Microscopy (SEM). The core radius Rc and hydrodynamic radius Rh of ASPB measured by Zeta Potential/Particle Sizer (ZLS) were ca. 50nm and (84.5±1) nm respectively. The percentage of grafting (PG%) of polyelec- trolyte brushes was 4.3% investigated by Thermo-gravimetric analysis (TGA). Detailed characterizations on ASPB were performed by cleaving the grafts from the anchoring surface. The molecular weight (Mw) and polydispersity (Mw/Mn) of brushes were 1.788·10 3 g/mol and 1.6 respectively from Gel Permeation Chromatography (GPC) measurements. Moreover, Rh and !-potential of ASPB in the presence of aqueous NaCl solutions of different concentrations were discussed.

Synthesis and characterization of polypyrrole doped with anionic spherical polyelectrolyte brushes

Synthesis and characterization of polypyrrole doped with anionic spherical polyelectrolyte brushes