Grafting Of Polyelectrolytes Research Articles

Layer-by-Layer Self-Assembly of Polyelectrolytes on Superparamagnetic Nanoparticle Surfaces.

Designing and manufacturing multifunctional nanoparticles (NPs) are of considerable interest for both academic and industrial research. Among NPs used in this field, iron oxide NPs show low toxicity compared to metallic ones and are thus of high interest for biomedical applications. In this work, superparamagnetic Fe3−δO4-based core/shell NPs were successfully prepared and characterized by the combination of different techniques, and their physical properties were investigated. We demonstrate the efficiency of the layer-by-layer process to graft polyelectrolytes on the surface of iron oxide NPs. The influence of the polyelectrolyte chain configuration on the magnetic properties of the Fe3−δO4/polymer core/shell NPs was enlightened. The simple and fast process described in this work is efficient for the grafting of polyelectrolytes from surfaces, and thus, derived Fe3−δO4 NPs display both the physical properties of the core and of the macromolecular shell. Finally, the cytotoxicity toward the human THP-1 monocytic cell line of the core/shell NPs was assessed. The results showed that the polymer-capped Fe3−δO4 NPs exhibited almost no toxicity after 24 h of exposure at concentrations up to 25 μg mL–1. Our results show that these smart superparamagnetic nanocarriers with stealth properties are promising for applications in multimodal cancer therapy, including drug delivery.

Superhydrophilic and underwater superoleophobic coatings on the basis of grafted polyelectrolytes on a textured aluminum surface

Water-loving compounds are usually used to prepare superhydrophilic and underwater superoleophobic surfaces. Hydrophilic polymers especially polyelectrolytes which contain the charged units in their structure is one of the perspective classes for the creation of materials with superhydrophilic properties. In this work, grafted polyelectrolytes based on quaternized N,N-dimethylaminoethyl methacrylate and sodium methacrylate were synthesized on the textured aluminum surface with an attached anchor layer (polyglycidyl methacrylate) and the initiator (2-bromo-2-methylpropionyl bromide) using surface-initiated atom transfer radical polymerization. The texturing of aluminum surface was performed using sequential etching in alkali and acid solutions. The lyophilic properties of grafted polyelectrolytes were studied by contact angle measurements using the “sessile drop” and “captive bubble” methods. The resulting coatings exhibit superhydrophilic properties due to quaternized ammonium and carboxyl charged groups in the grafted polyelectrolytes. Specifically, the coatings show complete wetting with water, stable aerophobicity and oleophobicity in aqueous media, and the demonstrated contact angles are greater than 170° for long contact times. It has been shown that grafting of polyelectrolytes prevents the sorption of nonpolar organic pollutants on the modified surface.

Noncovalent grafting of polyelectrolytes onto hydrophobic polymer colloids with a swelling agent

Often it is not feasible to graft hydrophilic polymer stabilizers covalently to polymer colloids as reactive binding sites are either not available or would interfere with the functional properties. Here, we present facile, general and scalable physical protocols for permanent noncovalent grafting of polyelectrolytes to hydrophobic polymeric nanoparticles with chemically inert surfaces using polyurea and polyurethane polymer nanocapsules as examples. The polyelectrolytes are adsorbed and physically entangled within a partially liquefied polymer surface upon adding a small amount of organic solvent as a swelling agent. Hydrophilic polyelectrolyte homopolymers and random copolymers were grafted upon overcoming unfavorable adsorption by adding salts and/or applying strong shear with sonication, with toluene as swelling agent. This grafting is reported either in an aqueous solution or by phase transfer from an oil phase to an aqueous phase in an oil/water emulsion. The resulting poly(2-acrylamido-2-methylpropanesulfonate, AMPS)-grafted nanocapsules exhibit long term (>1 month) colloidal stability in high salinity American Petroleum Institute (API) brine (8 wt.% NaCl and 2 wt.% CaCl2) at ambient and elevated temperature (50℃). Moreover, the mobility of the poly(AMPS)-grafted capsules in brine-saturated quartz sand is improved markedly compared to bare hydrophobic nanocapsules, given the electrosteric repulsion of the poly(AMPS) with the anionic quartz surface (mass breakthrough increased from 2% to 80.7%). These approaches are simple and generalizable to a wide range of polymer colloids where covalent grafting is either undesirable or impractical.

Making of porous ionic surfaces by sequential polymerization: polyurethanes + grafting of polyelectrolytes.

Making of porous ionic surfaces by sequential polymerization: polyurethanes + grafting of polyelectrolytes.

Swollen structure and electrostatic interactions of polyelectrolyte brush in aqueous solution

Abstract Surface grafting of polyelectrolytes on materials brings about various significant changes in surface properties such as wettability, adhesion, and friction, because of their excellent hydrophilicity and unique intermolecular interactions that depend on the ionic strength of the solution. This review paper describes the characterization of the swollen structure and electrostatic interaction of polyelectrolyte brushes in aqueous solution by use of optical tweezers and neutron reflectivity, in order to discuss the dissociation of ionic groups and charge distribution in the polyelectrolyte brush. In addition, the spreading and structure of water on the polyelectrolyte brush surface were characterized by high spatial resolution IR spectroscopy.

How does the ethoxylated grafting of polyelectrolytes affect the self-assembly of polyanion-cationic surfactant complex salts?

A cationic surfactant and different anionic copolymers randomly grafted with side chains of ethylene oxide were used to prepare stoichiometric complex salts. Variations in the length or proportion of side chains were shown to be responsible for affecting the surfactant phase behavior in water, resulting in the observation of a number of structures characterized by small angle X-ray scattering measurements, including a hierarchical micellar system and different liquid-crystalline phases. Additionally, although aqueous mixtures of stoichiometric complex salts usually phase separate, the presence of a sufficiently high weight fraction of ethylene oxide side chains can enhance the solubility of the complex salt aggregates in water over a wide range of concentration. Moreover, a dispersion of an isotropic concentrated solution of complex salts is formed at higher temperatures in a reversible process. In summary, this study proves the importance of the polyion structure for tuning the properties of systems of complex salts.

Grafting of polyelectrolytes onto hydrocarbon surfaces by high-energy hydrogen induced cross-linking for making metallized polymer films

Polyelectrolytes were grafted onto hydrocarbon surfaces by a dry-process and chemical-free approach using hydrogen projectiles with high kinetic energy but properly controlled to selectively cleave C-H bonds, on which electroless plating was carried out after loading Pd moieties by ion exchange, resulting in high quality metalized polymer films with excellent conductivity and mechanical stability.

Synthesis of pH-responsive polysilane with polyelectrolyte side chains through γ-ray-induced graft polymerization

Polysilanes with polyelectrolyte side chains are synthesized by two methods utilizing γ-ray-induced grafting and the pH responsiveness for one of those polymers is revealed mainly by investigating interfacial behavior of its monolayer at the air/water interface. In the first synthetic method, poly(methyl acrylate) is grafted onto poly(methyl- n-propylsilane) (PMPrS) through γ-ray-induced grafting, and then the PMA chains are hydrolyzed to poly(acrylic acid) resulting in the yield of ca. 97%. Thus PMPrS with polyelectrolyte side chains is successfully synthesized by the graft chain hydrolysis. The other method is the direct grafting of electrolyte monomers. Poly(methacrylic acid)-grafted PMPrS (PMPrS- g-PMAA) can be obtained through γ-ray-induced grafting of methacrylic acid monomers onto PMPrS chains, which shows the effectiveness of radiation grafting for the synthesis of polyelectrolyte graft copolymers. PMPrS- g-PMAA exhibits pH responsive behavior. In addition to the pH-dependence of water solubility, interfacial behavior also depends on the pH. Langmuir monolayers of PMPrS- g-PMAA exhibit different surface pressure–area isotherms according to the grafting yield and the pH of the subphase water. This result suggests that radiation modification is useful for fabricating polysilane-based ordered materials responsive to outer stimuli.

The molecular surface conformation of surface-tethered polyelectrolytes on PDMS surfaces

Surface properties of polymer materials are important for many applications such as biomedical materials, marine antifouling coatings, polymer membranes for biological and chemical molecule separations, and polymer adhesives. Surface properties are highly dependent on molecular surface structures. Presently, surface polymerization is one of the most effective methods to tailor and optimize molecular surface structures of many polymers. Herein, the surface structure of polydimethylsiloxane (PDMS) is modified by tethering polyelectrolytes (PEs) through surface-initiated ultraviolet (UV) polymerization. Using dimethylacrylamide, acrylic acid, and [2-(methacryloyloxy)ethyl]dimethyl(3-sulfopropyl)ammonium as monomers, cationic, anionic, and zwitterionic PEs are grafted onto PDMS surfaces using the “graft-from” method. Successful grafting of PEs onto PDMS surfaces has been verified by several analytical techniques, including Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurement. In particular, sum-frequency generation (SFG) vibrational spectroscopy has been employed to probe the molecular structure of modified PDMS surfaces in both the dry and hydrated states. It was found that in air, the surface dominating –Si–CH3groups of unmodified PDMS segregate to the PDMS surface along with the grafted PEs. These methyl groups have similar orientations to those on the unmodified PDMS surface: they more or less stand up on the surface, along the surface normal. Upon exposure to water, only SFG signals from the surface-tethered PE chains on the modified PDMS surface are observed, showing a substantial surface restructuring behavior. More details regarding such surface restructuring behavior can be deduced through SFG data analysis. With numerous PDMS applications in aqueous environments, it is of particular importance to modify its surface structures and characterize such surface structures in aqueous environments in situ.

Grafting of polyelectrolytes onto polyacrylamide by reactive processing

Low-molecular-weight high-charge-density cationic poly diallydimethyl ammonium chloride (polyDADMAC) was grafted onto nonionic polyacrylamide (PAM) using organic peroxide initiators in the molten state carried out in a batch mixer. The graft copolymer can be used as a high performance flocculant. Glycerol was selected as a plasticizer. The grafting reaction was characterized in terms of composition, temperature, degree of grafting, and grafting efficiency. It was found that free radicals on polymer chains were induced by the decomposition of the initiator. Grafting was produced by free radical recombination termination. The degree of grafting increases with an increase of the polyDADMAC/PAM feed ratio. However, the grafting efficiency was lower than 10 wt % in this highly viscous polymer melt system. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1412–1416, 1999

Hydrolysis and Subsequent Quaternization of Poly[(Isobutene-co-(m,p)-chloromethylstyrene)-g-2-methyl-2-oxazoline] and Poly((m,p)-Chloromethylstyrene-g-2-methyl-2-oxazoline)

The graft copolymers poly[(isobutene-co-(m,p)-chloromethylstyrene)-g-ethyleneimine)] HPG1 and poly((m,p)-chloromethylstyrene-g-ethyleneimine) HPG2 were obtained through the alkaline hydrolysis of the amphiphilic graft copolymers poly[(isobutene-co-(m,p)-chloromethylstyrene)-g-2-methyl-2-oxazoline] and poly((m,p)chloromethylstyrene-g-2-methyl-2-oxazoline), respectively. The subsequent quaternization of HPG1 and HPG2 with methyl iodide resulted in new polyelectrolyte graft copolymers which are soluble in water despite of the hydrophobic backbone.

96/00042 Demineralization and kerogen maceral separation and chemistry

Surface grafting of polyelectrolytes on materials brings about various significant changes in surface properties such as wettability, adhesion, and friction, because of their excellent hydrophilicity and unique intermolecular interactions that depend on the ionic strength of the solution. This review paper describes the characterization of the swollen structure and electrostatic interaction of polyelectrolyte brushes in aqueous solution by use of optical tweezers and neutron reflectivity, in order to discuss the dissociation of ionic groups and charge distribution in the polyelectrolyte brush. In addition, the spreading and structure of water on the polyelectrolyte brush surface were characterized by high spatial resolution IR spectroscopy.