Abstract: Nanoporous polyelectrolyte membranes with hierarchical and unique pore architectures can be readily made via electrostatic complexation between imidazolium-based poly(ionic liquid)s and poly(acrylic acid) in a variety of morphologies. Coating the membrane onto the surface of an optical fiber resulted in a device with high pH-sensing performance in terms of the response rate and the sensitivity, due to the charge and porous nature of the membrane layer.

Abstract: Radioactive counterions were used to track the ratio of positive to negative polymer repeat units within a polyelectrolyte multilayer made from poly(diallyldimethylammonium chloride), PDADMAC, and poly(styrene sulfonate), PSS. For this widely employed pair of “linearly” assembled polyelectrolytes it was found that the accepted model of charge overcompensation for each layer is incorrect. In fact, overcompensation at the surface occurs only on the addition of the polycation, whereas PSS merely compensates the PDADMAC. After the assembly of about a dozen layers, excess positive sites begin to accrue in the multilayer. Treating the surface as a reaction–diffusion region for pairing of polymer charges, a model profile was constructed. It is shown that different reaction–diffusion ranges of positive and negative polyelectrolyte charge lead to a blanket of glassy, stoichiometric complex growing on top of a layer of rubbery, PDADMAC-rich complex. Though overcompensation and growth was highly asymmetric with resp...

Abstract: Two flexible, oppositely charged polymers can form liquid-like complex coacervate phases with rich but poorly understood viscoelastic properties. They serve as an experimental model system for many biological and man-made materials made from oppositely charged macromolecules. We use rheology to systematically study the viscoelastic properties as a function of salt concentration, chain length, chain length matching, and mixing stoichiometry of model complex coacervates of poly(N,N-dimethylaminoethyl methacrylate), PDMAEMA, and poly(acrylic acid), PAA. The dynamics of making and breaking ionic bonds between the oppositely charged chains underlie all linear viscoelastic properties of the complex coacervates. We treat (clusters of) ionic bonds as sticky points and find that there is a remarkable resemblance between the relaxation spectra of these complex coacervates and the classical sticky Rouse model for single polymer systems. Salt affects all relaxation processes in the same way, giving rise to a widely a...

Abstract: The early reported pseudo-first-order reaction kinetics of the polymer-supported metallic nanocatalysts for the model reaction of p-nitrophenol (p-NP)/NaBH4 were probably oversimplified. Here a detailed study of p-NP reduction by NaBH4 in the presence of the raspberry-like poly(allylamine hydrochloride)-modified polymer poly(glycidyl methacrylate) composite sub-microspheres with tunable gold nanoparticles (PGMA@PAH@AuNPs) was presented. Effects of polyelectrolyte concentration, the ratio of polymer spheres to gold nanoparticles, and the solution pH value for composite synthesis on the induction period, reaction time, average reaction rate and average turnover frequency were systematically investigated. Experimental results in all cases of our study revealed an nth order (n > 1) of the p-NP/NaBH4 catalytic reaction by the prepared polymer composite particles. The apparent order of reaction, n, is dependent on the total surface area of the coated gold nanoparticles on the polymer spheres, which can be closely correlated with the tunable gold nanoparticle surface coverage. The mechanism of the observed catalytic activity enhancement was proposed based on active epoxy groups of the polymer spheres and a large adsorption of p-nitrophenolate anions onto the positively-charged spheres.

Abstract: Functional organic thin films often demand precise control over the nanometer-level structure. Interlayer diffusion of materials may destroy this precise structure; therefore, a better understanding of when interlayer diffusion occurs and how to control it is needed. X-ray photoelectron spectroscopy paired with C60+ cluster ion sputtering enables high-resolution analysis of the atomic composition and chemical state of organic thin films with depth. Using this technique, we explore issues common to the polyelectrolyte multilayer field, such as the competition between hydrogen bonding and electrostatic interactions in multilayers, blocking interlayer diffusion of polymers, the exchange of film components with a surrounding solution, and the extent and kinetics of interlayer diffusion. The diffusion coefficient of chitosan (M = ∼100 kDa) in swollen hydrogen-bonded poly(ethylene oxide)/poly(acrylic acid) multilayer films was examined and determined to be 1.4*10−12 cm2/s. Using the high-resolution data, we show that upon chitosan diffusion into the hydrogen-bonded region, poly(ethylene oxide) is displaced from the film. Under the conditions tested, a single layer of poly(allylamine hydrochloride) completely stops chitosan diffusion. We expect our results to enhance the understanding of how to control polyelectrolyte multilayer structure, what chemical compositional changes occur with diffusion, and under what conditions polymers in the film exchange with the solution.

Abstract: We present a paradigm that dramatically tunes friction from superior lubrication (μ ∼ 10–3) to ultrahigh friction (μ > 1) using responsive polyelectrolyte brushes. The tunable friction is based on counterion-driven interactions in polyelectrolyte brushes that can be simply achieved by exchanging the counterions. We systematically investigated the effects of opposite counterions of different types on the friction properties of polyanionic, polycationic, and polyzwitterionic brushes. For cationic brushes with quaternary ammonium groups, the friction coefficient was progressively tuned from ∼10–3 to ∼100 according to the counterions series Cl– < ClO4– < PF6– < TFSI–. The friction of anionic brushes can be tuned by oppositely charged surfactants (tetraalkylammonium) with different length of hydrophobic tails, multivalent metal ions, and protons. The friction increase of cationic brushes is due to the dehydration and the collapse of polyelectrolyte chains induced by ion-pairing interactions. For anionic brushe...

Abstract: Phase separation of polyelectrolyte complexes (PECs) between the polyacid (sodium salt) and polybase (hydrochloride) of poly(acrylic acid) (PAA) and poly(allylamine) (PAH), respectively, has been investigated in aqueous solution. Chain length of the PAA was varied (25 < Pw < 700) holding Pw of the PAH constant at 765. The polyacid/polybase mixing ratio (10–90 wt %) and the ionic strength as salt concentration (0–3,000 mM) were systematically varied. Sample turbidity was utilized as an indicator of PEC formation, complemented by optical microscopy for discrimination between precipitate and coacervate. Salt-free systems always resulted in PEC precipitates; however, coacervates or polyelectrolyte solutions, respectively, were formed upon exceeding critical salt concentrations, the PEC formation also depending on the employed PAA/PAH ratio. The lower the PAA molecular weight, the lower were the critical salt concentrations required for both the precipitate/coacervate and coacervate/solution transitions. The e...

Abstract: To improve lipid membrane stability and prevent leakage of encapsulated food ingredients, a polyelectrolyte delivery system (PDS) based on sodium alginate (AL) and chitosan (CH) coated on the surface of nanoliposomes (NLs) has been prepared and optimized using a layer-by-layer self-assembly deposition technique. Morphology and FTIR observation confirmed PDS has been successfully coated by polymers. Physical stability studies (pH and heat treatment) indicated that the outer-layer polymers could protect the core (NLs) from damage, and PDS showed more intact structure than NLs. Further enzymic digestion stability studies (particle size, surface charge, free fatty acid, and model functional component release) demonstrated that PDS could better resist lipolytic degradation and facilitate a lower level of encapsulated component release in simulated gastrointestinal conditions. This work suggested that deposition of polyelectrolyte on the surface of NLs can stabilize liposomal structure, and PDS could be developed as a formulation for delivering functional food ingredients in the gastrointestinal tract.

Abstract: Alkaline polymer electrolytes (APEs) are a new class of polyelectrolytes enabling the use of nonprecious metal catalysts in electrochemical devices, such as fuel cells and water electrolyzers. However, the current development of APEs is facing a severe difficulty, the conductivity–stability dilemma. Specifically, to acquire high ionic conductivity, the polymer backbone has to be grafted with enough cationic functional groups, typically quaternary ammonium (–NR3+), but such a modification in structure has damaged the chemical inertness of the polymer backbone and induced degradation in an alkaline environment. Here we demonstrate a strategy for disentangling such a dilemma. To alleviate the damage to the polymer backbone, we reduce the grafting degree (GD) of functional groups, but design two cations on each grafted functional group so as to retain sufficient ion concentration. Such a seemingly simple change in structure has brought a notable effect in performance: not only can both high ionic conductivity and much improved chemical stability be achieved, but also the intermolecular interaction between polymer chains has thus been enhanced, rendering the resulting APE membrane much stronger in mechanical strength and highly anti-swelling in water even at 80 °C.

Abstract: Section I General Biomaterial Applications of Polymers -- Biomedical Polymers in Theory and Practice -- Selected Examples of Pathologic Processes Associated with Human Polymeric Implants -- The Status of Olefin-SO2 Copolymers as Biomaterials -- Temporary Skin Substitute from Non-Antigenic Dextran Hydrogel -- Biomedical Applications of Poly(Amido-Amines) -- Covalent Bonding of Collagen and Acrylic Polymers -- Glow Discharge Polymer Coated Oxygen Sensors -- Section II Cardiovascular Applications of Polymers -- Progress and Problems in Blood-Compatible Polymers -- Biolized Material for Cardiac Prosthesis -- Plastic Materials Used for Fabrication of Blood Pumps -- Tissue Cultured Cells: Potential Blood Compatible Linings for Cardiovascular Prostheses -- Elastomeric Vascular Prostheses -- Morphology of Block Copolyurethanes. II. FTIR and ESCA Techniques for Studying Surface Morphology -- Section III Applications of Polymers in Medication -- Polymeric Drugs Containing 5-Fluorouracil and/or 6-Methylthiopurine. Chemotherapeutic Polymers. XI -- Polymeric Drugs: Effects of Polyvinyl Analogs of Nucleic Acids on Cells, Animals and Their Viral Infections -- Organometallic Polymers as Drugs and Drug Delivery Systems -- Polythiosemicarbazides as Antimicrobial Polymers -- The Biochemical Properties of Carrier-Bound Methotrexate -- Esterolytic Action of Water-Soluble Imidazole Containing Polymers -- Hydrolytic Degradation of Poly DL-(Lactide) -- Applications of Polymers in Rate-Controlled Drug Delivery -- Section IV Dental Materials Applications of Polymers -- Dental Polymers -- Polymer Developments in Organic Dental Materials -- Limiting Hardness of Polymer/Ceramic Composites -- New Monomers for Use in Dentistry -- The Synthesis of Fluorinated Acrylics Via Fluoro Tertiary Alcohols -- The Nature of the Crosslinking Matrix Found in Dental Composite Filling Materials and Sealants -- The Dental Plastics in the Future of Fixed Prosthodontics -- Initiator-Accelerator Systems for Acrylic Resins and Composites -- The Application of Photochemistry to Dental Materials -- Ionic Polymer Gels in Dentistry -- Adsorption and Ionic Crosslinking of Polyelectrolytes -- Effects of Microstructure on Compressive Fatigue of Composite Restorative Materials -- Wear of Dental Restorative Resins -- Friction and Wear of Dental Polymeric Composite Restoratives -- List of Contributors.

Abstract: We review the work done on complexes between biopolyelectrolytes such as ionically modified cellulose or chitosan and oppositely charged surfactants. Around equimolarity of the charges one typically observes precipitation but for other mixing ratios one may form long-time stable complexes, where structure and rheology depend on the mixing ratio, total concentration and the molecular constitution of the components. In addition, it may be the case that the structures are formed under non-equilibrium situations and therefore depend on the preparation path. The binding is shown to occur cooperatively and the micelles present often retain their shape irrespective of the complexation. However, the rather stiff biopolyelectrolytes may lead to an interconnection between different aggregates thereby forming a network with the corresponding rheological properties. In general, the structure and the properties of the aggregates are rather versatile and correspondingly one can create a wide range of different surfactant–biopolyelectrolyte systems by appropriately choosing the composition. This is very interesting as it allows for formulations with a large range of tuneable properties with ecologically friendly polyelectrolytes for many relevant applications.

Abstract: In this study, we report the preparation of pH tunable, temperature sensitive magnetoresponsive graphene-based nano-bio carriers for cellulase immobilization. We discuss a simple route to overcome the geometric disadvantage imposed by most 2D immobilization supports and make them capable of closely mimicking free enzymes (FE) operating under similar reaction conditions. The supramolecular assembly of oppositely charged quenched polyelectrolytes and maghemite–magnetite nanoparticles on 2D graphene supports followed by covalent immobilization of cellulase shows a marked improvement in the bio-receptivity of graphene supports. The incorporation of magnetic nanoparticles opens up the possibility of recovery and reuse of the enzyme over multiple cycles. The immobilized enzymes retained about 55% of the original specific activity even after four cycles of reuse. Cellulase immobilization is achieved by a combination of annealed polyelectrolyte brushes and zero-length spacer molecules. The swelling behavior of annealed polyelectrolyte brushes is a strong function of the environmental conditions. The degree of polyelectrolyte swelling can be easily tweaked by manipulating the pH and temperature, providing us an effective tool to control the activity of immobilized enzymes. At a pH of 5.1 and a temperature of 50 °C, the immobilized enzymes with the annealed polyelectrolyte brushes displayed close to 1.5-fold improvement in the activity as compared to immobilized enzymes without the brushes. Activity of immobilized cellulase is evaluated using both soluble as well as insoluble substrates like 2% (w/v) CMC and avicel respectively.

Abstract: To overcome alkali-resistant and synthetic hurdles to alkaline anion-exchange membranes (AAEMs) for alkaline fuel cells, the polyacylation of pre-quaternized monomers as a straightforward and versatile approach has been proposed for the first time. Via this approach, novel aromatic anion-exchange polyelectrolytes featuring a long pendent spacer (i.e., –O–(CH2)4–) instead of a conventional benzyl-type spacer (i.e., –CH2–) are successfully synthesized, and exhibit not only high OH− and CO32− conductivity (91 mS cm−1 and 51 mS cm−1 at 60 °C, respectively) but also outstanding alkaline stability (e.g., no degradation of ammonium groups after aging in 6 mol dm−3 NaOH at 60 °C for 40 days). Using this kind of AAEM, a promising peak power density of 120 mW cm−2 is obtained on a preliminary H2/O2 single cell at 50 °C. This powerful synthetic approach together with exceptional membrane properties should pave the way to the practical application of this kind of AAEMs in alkaline fuel cells.

Abstract: Fluorescence recovery after photobleaching has been applied to determine, to our knowledge for the first time, the molecular weight (Mw) dependence of lateral diffusion of polymer chains within layer-by-layer (LbL) films. As shown by neutron reflectometry, polyelectrolyte multilayers containing polymethacrylic acid (PMAA, Mw/Mn < 1.05) of various molecular weights assembled from solutions of low ionic strengths at pH 4.5, where film growth was linear, showed similar diffusion of PMAA in the direction perpendicular to the film surface. At a salt concentration sufficient for unfreezing electrostatically bonded chains, layer intermixing remained almost unaffected (changes <1.0 nm), while the lateral diffusion coefficient (D) scaled with the PMAA molecular weight as D ∼ Mw–1±0.05.

Abstract: Recent studies have revealed that a variety of shaped particles can interact with cells in a different way. Elongated particles can be effectively and quickly internalized intercellularly compared with other configurations. Herein we present the potential of fabrication of anisotropic polyelectrolyte multilayer capsules formed by coating spherical, ellipsoid-like and square calcium carbonate (CaCO3) particles. By varying the intermixing speed, time, pH value and ratio of initial ingredients during precipitation such CaCO3 templates are produced. Particles loaded with FITC–dextran and coated with polyelectrolytes could maintain the templated shape after core removal. Quantitative data are derived from analysis of confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) measurements.

Abstract: Multilayer microcapsules with a biconcave discoidal shape mimicking red blood cells (RBCs) are fabricated. The structure of the RBC-like microcapsules is verified by scanning electron and confocal laser scanning microscopies. The capsules show elastic deformation after being forced through a microcapillary with a smaller diameter, exhibiting a high recovery ratio of ≈90%. When the capsules are coated with hemoglobin (Hb),they are able to reversibly bind and release oxygen.

Abstract: The surface roughness of polyelectrolyte multilayers made from poly(diallyldimethylammonium chloride), PDADMAC, and poly(styrene sulfonate), PSS, was measured as a function of film deposition conditions. For dry multilayers, the significant roughness which builds up for thicker films is much more apparent for multilayers terminated with PSS. Corresponding roughness for PDADMA-capped multilayers may be seen by imaging in situ under electrolyte. Roughness may be substantially reduced, but not eliminated, by annealing in salt. Annealing does not lead to loss of polyelectrolyte from the film, even under conditions where the salt concentration is high enough to place the film properties beyond the glass transition. Roughness does not correlate with the molecular weight of the polyelectrolyte and is thus not caused by solution or film polymer chain conformations. The wavelength of the roughness features is approximately proportional to film thickness, which supports a mechanism whereby roughness is generated by...

Abstract: The thermal conductivity and heat capacity of surfactant and polyelectrolyte coatings of gold nanorods (GNRs) in aqueous solution are investigated by transient absorption, following femtosecond pumping of the longitudinal localized surface plasmons. Surfactant and polyelectrolyte layer thicknesses are measured by dynamic light scattering (DLS). The GNRs are initially coated with a bilayer of the quaternary ammonium surfactant cetyltrimethylammonium bromide (CTAB). The rate of change of the absorption of gold nanorods in aqueous solution varies with the probe laser wavelength due to the shift in the plasmon resonance created by heating of media around the particles. The cooling dynamics of gold nanorods are best measured by tuning the pump–probe laser wavelength to the absorption peak of the sample. The heat capacity of the surfactant layer is 2.0 ± 0.3 J cm–3 K–1; the thermal conductivity of the surfactant layer drops from 0.24 to 0.18 W m–1 K–1 at solution concentrations above the CTAB critical micelle c...

Abstract: Cholinium-based ionic liquid methacrylic monomers having halide, lactate and acetate counter-anions were synthesized and polymerized by using conventional free radical polymerization. The polymer properties were characterized by NMR, SEC/GPC, TGA, and DSC and compared among eight different cationic polymethacrylic analogs. Polycations with different methacrylic alkylammonium backbones having lactate anion displayed comparatively better thermal stability than those having the acetate counter-anions and they also exhibited lower glass transition temperatures than their counterparts having acetate and halide counteranions. As an application, cholinium lactate methacrylate ionic liquid monomer was used to prepare ion gels by photopolymerization. Interestingly, these are the first examples of ion gels which are fully composed of low toxicity and biocompatible cholinium ionic liquids. Furthermore, the same ionic liquid monomer, cholinium lactate methacrylate, showed the ability to dissolve cellulose. This facil...

Abstract: Bipolar membranes are laminated anion and cation exchange membranes that split water at their interface very efficiently upon application of an electric field. This paper investigates the layer-by-layer (LbL) deposition of polyelectrolyte multilayers, as a tool to introduce molecularly thin catalyst groups at this interface of bipolar membranes. The bipolar membranes were prepared by first modifying an anion exchange membrane by consecutive dipping LbL assembly, then casting a thin highly charged intermediate layer followed by casting a cation exchange layer. The results reveal that polyelectrolytes of higher charge density coated on the anion exchange layer yield better performance. Several parameters of the LbL interface deposition were varied. Out of the investigated LbL assembly parameters, ionic strength and number of layers have shown the largest influence on catalytic activity as well as ionic selectivity. The membrane with two bilayers of poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PE...

Abstract: Microcapsules of the herbicide picloram (PLR) were formulated by a layer-by-layer (LbL) self-assembly method using the polyelectrolyte biopolymers of biocompatible chitosan (CS) and the UV-absorben...

Abstract: Scale formation, the deposition of certain minerals such as CaCO3, MgCO3, and CaSO4·2H2O in industrial facilities and household devices, leads to reduced efficiency or severe damage. Therefore, incrustation is a major problem in everyday life. In recent years, double hydrophilic block copolymers (DHBCs) have been the focus of interest in academia with regard to their antiscaling potential. In this work, we synthesized well-defined blocklike PAA-PAMPS copolymers consisting of acrylic acid (AA) and 2-acrylamido-2-methyl-propane sulfonate (AMPS) units in a one-step reaction by RAFT polymerization. The derived copolymers had dispersities of 1.3 and below. The copolymers have then been investigated in detail regarding their impact on the different stages of the crystallization process of CaCO3. Ca2+ complexation, the first step of a precipitation process, and polyelectrolyte stability in aqueous solution have been investigated by potentiometric measurements, isothermal titration calorimetry (ITC), and dynamic ...

Abstract: This review concentrates on the interactions between oppositely charged polyelectrolytes and on the formation of complexes, which can be used for different applications such as paper retention or water treatment. Three different possibilities for the appearance of polyelectrolyte complexes (PECs) in flocculation applications are described. Starting with the “classical” dual system (step-by-step addition of polycation and polyanion to a negatively charged suspension of fibers or particles), the interaction between a “soluble polyanion” (such as anionic trash) with polycation is described as well as the formation of well-defined pre-mixed PECs and their application as flocculants.