Rheology of concentrated sulfonated poly(ether ether ketone) solutions

Sulfonated polyether ether ketone (SPEEK), an ionic polymer, has been shown to be a potential candidate for fuel cell electrolyte as a proton exchange membrane. Rheological behavior of SPEEK solutions is of great interest to understand the molecular associations as well as due to implications in membrane processing. In this work, SPEEK of various degrees of sulfonation (58–80) was prepared and rheology of concentrated solutions of SPEEK was studied. The rheological properties were evaluated using steady and oscillatory shear. It was found that steady shear viscosity and storage modulus at any given concentration, is the highest for the lowest degree of sulfonation SPEEK solutions in N‐methyl‐2‐pyrrolidone. The low frequency plateau in storage modulus was observed at some combinations of degrees of sulfonation and concentrations, indicating gel‐like behavior in these SPEEK solutions. No significant change in rheological behavior was observed with different polar solvents. Increase of several orders of magnitude in viscosity, storage and loss moduli were observed with increasing concentrations. The role of hydrophobic aggregation and inter‐chain associations in determining rheology of SPEEK solutions is argued based on comparisons with other material systems. The rheological behavior of SPEEK solutions with 70 as the degree of sulfonation, suggests crossover from hydrophobic‐hydrophilic balance. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40044.     

Effects of monovalent and multivalent ions on the stability of a polyelectrolyte complex with entrapped surfactants

In this article, we report the effects of nine different monovalent and multivalent salts on the particle size and stability of refined, positively charged polyelectrolyte complexes (PECs) with entrapped surfactant. Dynamic light scattering and ζ potential measurements of these polymeric particles as a function of various salt concentrations showed that both counter ions and co‐ions induced a concentration‐dependent increase in the particle size and a decrease in the ζ potential. We found that the anion concentration where the particle size doubled and the maximum anion concentration beyond which particle precipitation occurred (C_a,max) demonstrated a power law dependence on the anion valence. Moreover, for anions of the same valence but different hydration radio, C_a,max decreased in the following order: NO₃ → Cl → HPO₄^2? > SO₄^2? > PO₄^3?. However, unlike the case of hard colloids where co‐ions have relatively little effect on particle interactions, the co‐ions also increased the hydrodynamic radii of our PECs in the following order: K⁺ ≈ Na⁺ > Ca²⁺ > Mg²⁺ > Al³⁺. Furthermore, we found that the entrapped surfactants were shielded from the adverse effect of multivalent ions; this established that the monovalent and multivalent ions interacted with the polyelectrolyte shells of the PEC. This behavior was in contrast with the effect of salts on mixtures containing the polyelectrolyte and surfactant components, where the addition of salts typically causes an interaction with the individual components. Because several biomedical and technological applications involving PECs require saline environments, our studies provide insight into how small ions influence the PEC stability in applications involving varying salinities. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42099.     

Studies on self‐assembly and characterization of polyelectrolytes and organic dyes

Four polyelectrolyte complexes were formed through self‐assembly of poly‐N‐ethyl‐N,N‐(dimethylamino)ethyl methacrylate (PEDEM) and poly‐N‐ethyl‐4‐vinylpyridinium (PEVP) cations with methyl orange (MO) and metanil yellow (MY) anions in water. The FTIR spectra showed that the assembly was formed chiefly through electrostatic force and hydrophobic interaction between polyelectrolytes and organic dyes without new bonds emerging. The fluorescence spectra revealed that the emission waves of the complexes of PEDEM–MY and PEDEM–MO in alcohol were blue‐shifted in comparison with that of dyes in alcohol, and the emission waves of the PEVP–MY and PEVP–MO_ complexes in alcohol were red‐shifted in comparison with that of dyes in alcohol. The structure of the complexes in the solid state were also investigated by DTA and X‐ray diffraction experiments. It could be proved that the complexes were new materials formed through weak interactions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 369–374, 2003     

Use of a CO2‐switchable hydrophobic associating polymer to enhance viscosity–response

A series of copolymers, poly(acrylamide)‐co‐poly(N,N‐dimethylaminoethyl methacrylate)‐co‐poly(N‐cetyl DMAEMA) (abbreviation PDAMCn), was synthesized with different monomer ratios. The resulting copolymer solution shows pronounced viscosity–response property which is CO₂‐triggered and N₂‐enabled. Electrical conductivity experiment shows that tertiary amine group on DMAEMA experiences a protonate and deprotonate transition upon CO₂ addition and its removal. In addition, different incorporation rates of DMAEMA leads to two kinds of morphological change in the presence of CO₂ and thus induces different rheological behaviors. PDAMCn incorporating longer hydrophobic monomer (C₁₈DM) show more pronounced initial viscosity and higher critical stress required to cause network deformation, which consequently enhances the viscosity–response property of the solution. The addition of NaCl could also tune the viscosity of PDAMCn solution. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41468.     

Studies on the electrostatic self‐assembly of polyelectrolytes and organic dyes with atomic force microscopy

An ultrathin film was formed by the electrostatic self‐assembly of polyelectrolyte poly‐N‐ethyl‐N,N‐dimethyaminoethyl methacrylate (PDMAEB) and the organic dye metanil yellow (MY) on a smooth glass sheet. An atomic force microscope was used to study the topography and the phase of the two samples and the ultrathin film (PDMAEB–MY). The dynamic course of the surface structure was researched by atomic force microscopy also. It is illustrated that the existence of electrostatic interactions between PDMAEB and MY made MY arrange in order on the polyelectrolyte surface. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1029–1033, 2003     

Electron spin resonance study and reactive extrusion of polyacrylamide and polydiallyldimethylammonium chloride

In this article we report results from an experimental investigation on reactive extrusion of water‐soluble polymers. A polymer system containing homopolymers of diallyldimethylammonium chloride (PolyDADMAC) and acrylamide (PAM) was chosen for this study. Reactive extrusion was performed in a counter‐rotating, tangential twin screw extruder using glycerol as a plasticizer and 2,5‐dimethyl‐2,5‐di‐(t‐butylperoxy) hexene‐3 (Lupersol 130) as an initiator. The effects of three processing parameters (polyDADMAC/PAM weight ratio, extrusion temperature, and residence time) on grafting efficiency and degree of grafting of polyDADMAC on PAM were examined. We found the grafting efficiency of polyDADMAC onto PAM decreased with increasing extrusion temperature, polyDADMAC/PAM weight ratio, and residence time. The degree of grafting of polyDADMAC increased with increasing polyDADMAC/PAM weight ratio, but decreased with increasing extrusion temperature and residence time. The insoluble gel fraction in the extruded copolymer increased with increasing extrusion temperature and residence time, but decreased with increasing polyDADMAC/PAM weight ratio. The chemistry and free radical mechanism of PAM‐peroxide and polyDADMAC‐peroxide systems were studied for three different peroxides using an electron spin resonance technique. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1154–1164, 2000     

Pervaporation separation of sodium alginate/chitosan polyelectrolyte complex composite membranes for the separation of water/alcohol mixtures: Characterization of the permeation behavior with molecular modeling techniques

Polyelectrolyte complex (PEC) membranes were prepared by the complexation of protonated chitosan with sodium alginate doped on a porous, polysulfone‐supporting membrane. The pervaporation characteristics of the membranes were investigated with various alcohol/water mixtures. The physicochemical properties of the permeant molecules and polyion complex membranes were determined with molecular modeling methods, and the data from these methods were used to explain the permeation of water and alcohol molecules through the PEC membranes. The experimental results showed that the prepared PEC membranes had an excellent pervaporation performance in most aqueous alcohol solutions and that the selectivity and permeability of the membranes depended on the molecular size, polarity, and hydrophilicity of the permeant alcohols. However, the aqueous methanol solutions showed a permeation behavior different from that of the other alcohol solutions. Methanol permeated the prepared PEC membranes more easily than water even though water molecules have stronger polarity and are smaller than methanol molecules. The experimental results are discussed from the point of view of the physical properties of the permeant molecules and the membranes in the permeation state. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2634–2641, 2007     

Synthesis,characterization, and self‐assembly of cationic coumarin side‐chain polymer

In this study, the synthesis of a novel cationic coumarin‐containing polymer (C‐CPA) was presented. C‐CPA was examined optically using photoluminescence (PL) spectroscopy. The optical data suggested that they were promising blue‐emitting materials mainly due to the coumarin chromophore on the side chain. Moreover, the synthesized cationic polymer was suitable for layer‐by‐layer electrostatic self‐assembly thin film deposition from dilute polymer solution and multilayers were fully characterized by UV–vis spectroscopy, PL spectroscopy and atomic force microscope. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Coating of polyelectrolyte multilayer thin films on nanofibrous scaffolds to improve cell adhesion

The adhesion of L929 cells to poly(?‐caprolactone) (PCL) nanofibers was successfully improved via coating with polyelectrolyte multilayer thin films (PEMs), which enhanced the potential of this material as a scaffold in tissue engineering applications. With the electrostatic self‐assembly technique, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4‐styrene sulfonate) (PSS) were formed as four‐bilayer PEMs on electrospun PCL nanofiber mats. Because PDADMAC and PSS are strong polyelectrolytes, they provided stable films with good adhesion on the fibers within a wide pH range suitable for the subsequent processes and conditions. PDADMAC and gelatin were also constructed as four‐bilayer PEMs on top of the PDADMAC‐ and PSS‐coated nanofibers with the expectation that the gelatin would improve the cell adhesion. L929 cells from mouse fibroblasts were then seeded on both uncoated and coated scaffolds to study the cytocompatibility and in vitro cell behavior. It was revealed by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay that both the uncoated and coated nanofiber mats were nontoxic as the cell viability was comparable to that of those cultured in the serum‐free medium that was used as a control. The MTT assay also demonstrated that cells proliferated more efficiently on the coated nanofibers than those on the uncoated ones during the 48‐h culture period. As observed by scanning electron microscopy, the cells spread well on the coated nanofibers, especially when gelatin was incorporated. The surface modification of PCL nanofiber mats described in this research is therefore an effective technique for improving cell adhesion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and monovalent selective properties of multilayer polyelectrolyte modified cation‐exchange membranes

This study reports the modification of commercial cation‐exchange membrane by layer‐by‐layer adsorption of polyethyleneimine and poly(acrylic acid) (PAA) to endow them with monovalent ion selectivity. The chemical and morphological changes of the modified membrane surface were examined by ATR‐FTIR and SEM, respectively. The permselectivity for monovalent cations of the membranes was investigated by electrodialysis experiments. The effects of deposited bilayer number, the salt concentration, and pH of the dipping polyelectrolyte solutions on selectivity were investigated. Meanwhile, the resistance of membranes was measured taking energy consumption into consideration. The polyelectrolyte multilayer was crosslinked using epichlorohydrin to improve stability, and the durability of the composite membrane was studied. Separation mechanism of the composite membrane was also investigated. It is demonstrated that the bivalent cations are mainly rejected by electrostatic repulsion from the positive charge on the surface of the composite membranes. The sieving effect of the dense structure of skin layer becomes more pronounced with the number of deposited layers increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41488.     

Synthesis and association properties in water solution of random copolymers of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid and isodecyl methacrylate—potential application as surfactants in micellar‐enhanced ultrafiltration processes

Hydrophobically modified water‐soluble polymers have been prepared by copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and isodecyl methacrylate (iDMA) in N,N‐dimethylformamide under nitrogen atmosphere, varying the composition feed. Fluorescence spectroscopy was used to further confirm the copolymers self‐aggregate in water. Critical concentration of the self‐aggregate formation (CAC) decreased by increasing the molar fraction of iDMA in the AMPS_co copolymers and varied between 1.20 and 0.04 g/L depending on the degree of hydrophobic modification. Hence, copolymer composition and charge density allowed tuning the pseudomicellar characteristics of these new amphiphilic copolymers. The addition of a salt or a low‐molecular‐weight surfactant was studied. Binding of CTAB to the AMPS_co copolymers leads to a high decrease of CAC, i.e., 0.006 g/L. Effect of the composition in the viscosimetric behavior of the hydrophobically modified copolymers AMPS_co was investigated. The removal of single metal ions, Cu²⁺, and m‐cresol from aqueous solutions by ultrafiltration with the help of the copolymers was investigated. Equilibrium dialysis experiments demonstrate that the formation of hydrophobic microdomains can be used to control the sequestration of foulants, and thus these novel copolymers have potential application as polymeric surfactants in micellar‐enhanced ultrafiltration processes for water purification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Modification of SPPESK proton exchange membranes through layer‐by‐layer self‐assembly

Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) composite membranes are fabricated through electrostatic layer‐by‐layer (LbL) self‐assembly method with chitosan (CS) and phosphotungstic acid (PWA) to enhance the proton conductivity and stability. The results demonstrate that LbL self‐assembly has different effects on the SPPESK membrane substrates with different sulfonation degrees (DSs). It elevates proton conductivity of the SPPESK membrane of lower DS and enhances swelling stability of the SPPESK membrane of higher DS. For instance, at 80°C, proton conductivity of the SPPESK0.74/(CS/PWA)₁ membrane (lower DS) increases by 16%–96.49 mS cm^?1, and swelling ratio of the SPPESK1.01/(CS/PWA)₃ membrane (higher DS) decreases from 58 to 29%. Attribute to the electrostatic interaction and ion cross‐linking networks, permeability of the SPPESK0.74/(CS/PWA)₃ membrane and the SPPESK1.01/(CS/PWA)₅ membrane are reduced by 45 and 30%, respectively. The results indicate that the LbL self‐assembly has broadened the available DS range for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42867.     

Self‐assembly of bovine serum albumin and poly(acrylic acid) induced by noncovalent bonds

Bovine serum albumin/poly(acrylic acid), BSA/PAA, nano‐scaled particles were produced by noncovalent bonds induced self‐assembly method at acid pH area. Proper conditions during preparation process, such as pH value, BSA/PAA weight ratio(WR), PAA molecular weight, were researched by studying the hydrodynamic diameter, polydispersity index, and ζ potential of the nanoparticles. Complex formation between BSA and PAA was studied by FT‐IR, AFM, and TEM. BSA chains are supposed to be partly trapped in the nanoparticles core after interaction with PAA because of the electrostatic attractions and hydrogen bonds interactions between BSA and PAA, while the rest of the BSA chains should form the shell of the nanoparticles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Interaction between iodine and ethyl cellulose

Interaction between iodine and ethyl cellulose was investigated by immersing ethyl cellulose membranes in aqueous iodine–iodide solution (iodine doping) and incorporating iodine in the solution from which the membrane was cast. Oxygen and nitrogen permeabilities in iodine‐doped ethyl cellulose decrease with an increase in the concentration of iodine in the dopant solution up to 0.003 mol L⁻¹ and increase sharply at higher iodine concentrations, and ultraviolet–visible and far‐infrared spectra indicate formation of a charge transfer complex. Differential scanning calorimetry of both types of membrane shows changes in the characteristic phase transitions of ethyl cellulose after iodine treatment, including the crystal–liquid crystal transition that has been reported to occur in ethyl cellulose. Further evidence for liquid crystal phases has been found from circular dichroism. X‐ray photoelectron spectroscopy of iodine‐doped ethyl cellulose films indicates that the iodine is present in two different chemical states, probably l and l₂. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1303–1314, 1999     

Polymer clay self‐assembly complexes on paper

Layer‐by‐layer (LBL) self‐assembly was used to form polymer/clay complexes on paper to enhance its wet strength properties. Initially, alternating layers of poly(allylamine hydrochloride) (PAH) and Kaolin clay were sequentially deposited on quartz substrate and characterized by UV/Vis/NIR spectroscopy as a model system. The same procedure was then applied to a paper test sheet to form multilayered coatings, which were examined with scanning electron microscopy. The wettability of the LBL coated paper test sheet was shown to change from hydrophilic to hydrophobic with increased number of multilayers and if the terminating layer was Kaolin clay. The wet strength of the coated test sheet was improved by more than 270% over the uncoated test sheet with 16 bilayers of PAH/kaolin complex on the surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

All‐trans retinoic acid release from polyion‐complex micelles of methoxy poly(ethylene glycol) grafted chitosan

We synthesized a methoxy poly(ethylene glycol) grafted chitosan (ChitoPEG) copolymer to prepare a retinoic acid (RA) encapsulated polymeric micelle. The RA‐encapsulated polymeric micelle of the ChitoPEG copolymer had a particle size of 100–500 nm and a spherical shape when observed by transmission electron microscopy. In a ¹H‐NMR study, the specific peaks of RA and chitosan as a drug‐carrying inner core disappeared in deuterium oxide, and only the specific peak of methoxy poly (ethylene glycol) (MPEG) was observed, whereas specific peaks of MPEG, RA, and chitosan appeared in dimethyl sulfoxide. This indicated that the RA/ChitoPEG ion complexes were composed of a polymeric micelle with a core–shell structure and that free drug did not exist in the polymeric micelle formulations. Other evidence of drug incorporation into the polymeric micelle was witnessed in a differential scanning calorimetry analysis. The melting peaks of RA and chitosan were 182 and 220°C, respectively. The melting peak of the polymeric micelle was 200°C, whereas the melting peaks of the physical mixtures were those of both RA and the ChitoPEG copolymer. The lyophilized polymeric micelle was successfully reconstituted into phosphate‐buffered saline without the aid of cryoprotectants. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Sorption/release of diclofenac sodium in/from free‐standing poly(acrylic acid)/poly(ethyleneimine) multilayer films

Polyelectrolyte multilayer films deposited onto various substrates have been used extensively as drug delivery systems. However, little attention has been paid to the release of drugs from free‐standing polymeric films. Herein, we report the construction of thermal crosslinked free‐standing poly(acrylic acid) (PAA)/branched poly(ethyleneimine) (PEI) multilayer films composed of 25 double layers [(PAA/PEI)₂₅] and their use in sorption/release of diclofenac sodium (DS). The (PAA/PEI)₂₅ multilayer films were characterized by scanning electron microscopy, potentiometric titrations and Fourier transform infrared spectroscopy, while the sorption/release of DS was monitored by UV – Vis spectroscopy. The DS sorption equilibrium data were fitted with five isotherm models (Langmuir, Freundlich, Sips, Dubinin–Radushkevich, and Temkin). The maximum equilibrium sorption capacity, q_m, given by the Langmuir model was 32.42 mg DS/g. The Korsmeyer–Peppas semiempirical equation showed that the release of DS from the free‐standing (PAA/PEI)₂₅ films proceeded by pseudo‐Fickian diffusion, irrespective of the releasing media. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43752.     

Self‐assembly of alginate/polyethyleneimine multilayer onto magnetic microspheres as an effective adsorbent for removal of anionic dyes

A novel magnetic adsorbent alginate/polyethyleneimine (ALG/PEI)_n/MN was developed for removal of anionic dyes from aqueous solution in this study. (ALG/PEI)_n/MN was prepared by depositing ALG/PEI multi‐layers onto amine‐modified Fe₃O₄ microspheres through layer‐by‐layer method. The morphologies and structures of the adsorbent were characterized by scanning electron microscopy, X‐ray diffractometer, and Fourier transform infrared spectrometer, respectively, and its performance in adsorption of anionic dye (acid orange 10, AO10) under varied experimental conditions were also investigated. The results revealed that the uptake capacity of AO10 by (ALG/PEI)_n/MN increased with the number of coated (ALG/PEI) bilayer on the adsorbents, and the maximum adsorption capacity for AO10 by (ALG/PEI)₄MN was 246.3 mg g^?1 at 25 °C. The adsorption process was exothermic and well described by the pseudo‐second order kinetic model and the Langmuir isothermal model. Moreover, (ALG/PEI)₄/MN showed good reusability and excellent magnetic separability. All the results demonstrate that (ALG/PEI)₄/MN is a potential recyclable adsorbent for removal of anionic dyes from wastewater. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45876.     

Layer‐by‐layer self‐assembly of a lignin–poly(vinyl alcohol) based polyelectrolyte with a conductivity method

In this study, we made a new attempt to examine the relationship between the conductivity and the concentration of a polyelectrolyte solution and to prepare multilayer films with cationic lignin and polyanions through layer‐by‐layer self‐assembly. The nitrogen content of trimethyl lignin quaternary amine salt (TLQA) was 3.56%, and the carboxyl content of carboxymethylated poly (vinyl alcohol) (CMPVA) was 0.62 mmol/g. Attenuated total reflectance spectra confirmed that TLQA and CMPVA were fabricated and assembled successfully. The concentration of TLQA had a polynomial correlation with the conductivity [correlation coefficient (R²) = 0.9953], and the concentration of CMPVA was linear with the conductivity (R² = 0.9819). The electrostatic sequential adsorption process was monitored with a UV–visible spectrophotometer, and the morphology of the (TLQA/CMPVA)_n (where n is the number of double membranes) multilayer film was observed by atomic force microscopy and scanning electron microscopy. When the absorbance of the (TLQA/CMPVA)_n multilayer film increased linearly, the linear equation was y = 0.0267x + 0.07453 and R² was 0.9735. When five layers of TLQA and CMPVA were assembled, the surface root mean square roughness of TLQA and CMPVA were 21.07 and 65.28 nm, respectively. When the number of layers increased, the film surface roughness increased. The stability of the multilayer films in aqueous solution was determined by a conductivity meter. The (TLQA/CMPVA)_n multilayer film was stable in water. The results of the research demonstrate for the first time that TLQA and CMPVA could be assembled and successfully driven by electrostatic forces. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44416.     

Self‐assembly properties of ultra‐long‐chain gemini surfactant with high performance in a fracturing fluid application

A new cationic gemini surfactant (C25‐6‐C25), which had a special structure consisting of ultra‐long hydrophobic chains and amide groups, was synthesized using a main feedstock source obtained from rapeseed for thickening purposes. The 12 mmol L^?1 C25‐6‐C25 fluid containing 0.19 mol L^?1 potassium chloride (KCl) exhibited highly elastic properties at the angular frequency of 0.04–10 rad s^?1. Its viscosity could be maintained at 55 mPa s for 1.5 h under a shear rate of 170 s^?1 at 110 °C and it also showed a good proppant‐suspending property. C25‐6‐C25/KCl fluid exhibited high viscoelasticity and good performance, which were attributed to intermolecular forces, hydrogen bonding, and the shielding effect of electrostatic repulsion by KCl. Thus, C25‐6‐C25 is a very promising candidate for fracturing. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44602.