Polyampholyte Polymers Research Articles

Polyampholyte-grafted silica nanoparticles for shale plugging under high-temperature and extreme-salinity conditions

Nano-/submicron-scale plugging is critical for wellbore stability during shale gas exploitation but typically fails under high-temperature and extreme-salinity conditions due to colloidal instability. Herein, polyampholyte polymers (ZP) were grafted from the surface of silicon dioxide (SiO2) nanoparticles through surface-triggered free radical polymerization to generate nanoplugging additives (SiO2-g-ZP). SiO2-g-ZP exhibited excellent colloidal dispersion stability with a nano/submicron size distribution in 35 w/v% sodium chloride (NaCl) and 11 w/v% calcium chloride (CaCl2) brines at 160 °C for a long time and over a wide pH range, and efficiently plugged 220 nm and ∼20 μm pores and 5 μm fractures at 160 °C and 3.5–5.5 MPa. Three critical aspects of observation and analysis obtained through microstructure analysis and molecular dynamics (MD) simulations helped elucidate the mechanisms that control the SiO2-g-ZP's performances: an increase in SiO2-g-ZP's hydration capability with salinity due to the antipolyelectrolyte behaviours of ZP coatings with zwitterionic nature, an efficient mitigation of Na-bent agglomeration even at harsh conditons due to the preferential adsorption of SiO2-g-ZP rather than Na+, Ca2+ and Cl− on Na-bent, and the presence of a nanosilica core and rigid groups and massive hydratable groups. The first two aspects caused a perfect matching of particles in muds to pores and fractures in formation and the third aspect helped enhance the SiO2-g-ZP's thermal resistance and residence in the pores and fractures. This work provides a novel approach that can be broadly generalized to address the thermal- and salt-tolerance challenges of colloidal systems used in the exploration and development of deep and complex shale formations.

Delivery of Bioactive Albumin from Multi-Functional Polyampholyte Hydrogels.

Tissue engineered scaffolds are currently being explored to aid in healing and regeneration of non-union fractures in bone. Additionally, albumin has been demonstrated to provide benefits to healing when applied to injury sites. This paper focuses on delivery of calcium modified, bioactive bovine serum albumin (BSA) from a multi-functional polyampholyte polymer scaffold. First, the inherent nonfouling and conjugation properties of the polyampholyte hydrogel were verified to determine the impact of calcium exposure. The polyampholyte hydrogel delivery platform was then assessed with calcium titrations and osteoblast-like cell (MC3T3-E1) adhesion, proliferation, and viability evaluations. Finally, integrin inhibitors were used to identify the binding mechanisms that mediate cell adhesion to the calcium-modified BSA-conjugated hydrogels. An increase in cell adhesion was observed following calcium exposure up to 0.075 M, although this and higher calcium concentrations affected hydrogel stability and cell growth. BSA exposed to 0.05 M calcium and delivered from polyampholyte hydrogels promoted the most promising viable cell adhesion over 7 days. Cell adhesion to the calcium-modified BSA-conjugated hydrogels appeared to be regulated by arginine-glycine-aspartic acid (RGD) and collagen specific integrins. These results demonstrate that the delivery of calcium modified BSA from an implantable polymer scaffold is promising for bone tissue engineering applications.

Impacts of cross-linker chain length on the physical properties of polyampholyte hydrogels.

Polymeric tissue engineering scaffolds have shown promise to aid in regeneration and repair of damaged tissue. In particular, nonfouling polymers have been proposed for eliminating biomaterial-induced concerns such as infection, scarring, and rejection by the immune system. Polyampholyte polymers are one class of nonfouling polymers that are composed of an equimolar mixture of positively and negatively charged monomer subunits. They possess nonfouling properties, bioactive molecule conjugation capabilities, and tunable mechanical properties. In this study, the influence of the cross-linker species on the degradation behavior, mechanical strength, and nonfouling properties of polyampholytes composed of a 1:1 molar ratio of [2-(acryloyloxy)ethyl] trimethylammonium chloride (positively charged) and 2-carboxyethyl acrylate (negatively charged) monomers was investigated. Specifically, the impact of ethylene glycol repeat units on the overall material performance was evaluated by synthesizing and characterizing hydrogels containing di-, tri-, and tetra-ethylene glycol dimethacrylate cross-linker species. The degradation studies were conducted for over 100 days in Sorenson's buffer with pH values of 4.5, 7.4, and 9.0 by tracking the swelling behavior and weight change over time. The mechanical properties were assessed using compression and tensile testing to failure. The retention of the nonfouling and protein conjugation capabilities was demonstrated using fluorescently labeled bovine serum albumin. The results demonstrate the tunability of both degradation behavior and mechanical properties through the cross-linker selection, without impacting the underlying nonfouling and biomolecule delivery capabilities. Therefore, it is concluded that polyampholyte hydrogels represent a promising platform for tissue engineering.

New Polyampholyte Polymers Based on Polypropylene Glycol Fumarate with Acrylic Acid and Dimethylaminoethyl Methacrylate

The possibility of preparing new polyampholyte polymers based on polypropylene glycol fumarate–acrylic acid–dimethylaminoethyl methacrylate terpolymers was demonstrated. The main relationships of radical terpolymerization in dioxane, including binary systems participating in the terpolymerization, were studied. The block lengths, transition probabilities, and Harwood block structure parameter were calculated for the terpolymers from the copolymerization constants for the binary systems. These parameters reflect the arrangement of the macroradicals in the chain. The morphology of the polymer surface was studied by scanning electron microscopy, and the surface pore size was estimated. The influence of organic solvents and pH on the sample swelling was studied, and the isoelectric point (pH 6.00) of the terpolymer was determined.

Drilling mud with addition of new hydration inhibitor for clay rocks

While drilling through clay rocks using water-based mud, number of challenges need to be faced in view of hydration and swelling of this type of rock. Those phenomena consist in the fact, that clay mineral grows in volume due to water contact. In order to limit hydration phenomenon, for clay rocks drilling are used drilling muds with addition of chemical agents called hydration inhibitors. The article describes studies, which resulted in development of new formula of drilling mud with addition of a new short-chained amino polymer developed in Drilling, Oil and Gas Faculty AGH-UST Krakow. For the developed mud, tests of technological parameters were conducted according to API RP 13B-1 as well as specialist examinations: linear swelling of Miocene shale and clay rock disintegration. Studies also consists of syntheses of polyampholyte and short-chained cationic polymer. Based on performed studies, it was found that studied mud is characterized by good and easy to regulate technological parameters as well as effective inhibition of hydration, swelling and disintegration of clay rocks.

Polyampholyte Hydrogels in Biomedical Applications.

Polyampholytes are a class of polymers made up of positively and negatively charged monomer subunits. Polyampholytes offer a unique tunable set of properties driven by the interactions between the charged monomer subunits. Some tunable properties of polyampholytes include mechanical properties, nonfouling characteristics, swelling due to changes in pH or salt concentration, and drug delivery capability. These characteristics lend themselves to multiple biomedical applications, and this review paper will summarize applications of polyampholyte polymers demonstrated over the last five years in tissue engineering, cryopreservation and drug delivery.

Tunable multifunctional tissue engineering scaffolds composed of three‐component polyampholyte polymers

ABSTRACTResistance to nonspecific protein adsorption and the capability to provide targeted bioactive signals are essential qualities for implantable biomaterials. The development of materials that combine these multifunctional characteristics and tunable mechanical properties has been a target in the tissue engineering field over the last decade. This study is the first to demonstrate that polyampholyte hydrogels prepared with equimolar quantities of positively charged and negatively charged monomer subunits from multiple monomer compositions have great potential to address these needs. The hydrogels were synthesized with positively charged [2‐(acryloyloxy)ethyl] trimethylammonium chloride and different monomer ratios of the negatively charged 2‐carboxyethyl acrylate and 3‐sulfopropyl methacrylate monomers. The physical and chemical properties of the hydrogels were fully characterized, including swelling, hydration, mechanical strength, and chemical composition, and the fouling resistance of the hydrogels was demonstrated using enzyme‐linked immunosorbent assays. Additionally, the capability of the hydrogels to facilitate protein conjugation via EDC/NHS conjugation chemistry was assessed. The results clearly demonstrate that the polyampholyte hydrogels have a range of tunable mechanical strength based on the monomer subunits, while maintaining their excellent nonfouling properties. Additionally, high levels of conjugated protein were achieved for all of the monomer combinations investigated. Therefore, the broadly applicable multifunctional properties of polyampholyte hydrogels and their tunable mechanical properties clearly demonstrate the potential of these materials for tissue engineering. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43985.

Polyampholyte polymer as a stabiliser for subgrade soil

This study evaluates the potential of selected ionic polymers to act as pavement subgrade binders. Investigations were based on their relative performance with a Qatari soil which was selected as typical of a pavement subgrade to be found in the Middle East and North African region. The polymeric binders chosen were three synthetic ionic variations of polyacrylamide: cationic poly(acrylamidopropyl trimethyl ammonium chloride) (designated PAMTAC), anionic hydrolysed poly(acrylamide) (HPAM) and the ampholitic terpolymer poly(acrylamide-co-sodiumacrylate-co-(3-acrylamidopropyl) trimethylammonium chloride) (TPAM). The polymers were characterised by Fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic spectroscopy (1H-NMR and 13C-NMR). The comparative performance of the polymer-treated soil was judged on the basis of results obtained from selected standard mechanical test data: specifically, the unconfined compressed strength, the stiffness modulus and the toughness. It is concluded that a 50% w/w aqueous solution of the ampholitic terpolymer applied at a dosage of 2.0% by dry weight of the soil gives the best subgrade stabilisation. Of some significance, it is further noted that this ampholitic polymer was superior as a binding agent to the traditional standard, Portland cement, judged under equivalent but nonstandard conditions. Modifying the polymer to act as a binder for subgrade soils in general is also discussed.

PH responsive graft copolymers of chitosan

Grafting suitable polymers onto chitosan can produce cationic or polyampholyte polymers or hydrogels that are potential smart biomedical materials. Chitosan-graft-[poly(diethylamino)ethyl methacrylate] has been prepared in three different physical forms as linear free chains in solution, chemical gels crosslinked with glutaraldehyde, and poly(diethylamino)ethyl methacrylate] grafted onto chitosan tripolyphosphate gel beads. In addition to chemical structure, the graft copolymers were characterized with respect to their dissolution and swelling behavior in aqueous solution. It has been established that solubility of the products is controlled by the grafting yield. While pH sensitive polymers, which collapse at a given pH value are obtained at lower grafting yields, hydrogels form at higher grafting yields with pH responsive swelling behavior. Glutaraldehyde crosslinked chitosan-graft-[poly(diethylamino)ethyl methacrylate] gels and chitosan tripolyphosphate gel beads grafted with poly[(diethylamino)ethyl methacrylate] exhibit pH sensitive swelling with highest equilibrium swelling capacity at pH=1.2.

Preparation and study on the volume phase transition properties of novel carboxymethyl chitosan grafted polyampholyte superabsorbent polymers

A series of promising and novel polyampholyte superabsorbent polymers (CMCTS-g-P(AA-co-LCADMAAC)) were prepared using carboxymethyl chitosan (CMCTS) as skeleton accompanied with graft copolymerization of acrylic acid (AA) and long-chain alkyl dimethyl allyl quaternary ammonium salts (LCADMAAC). The structure of LCADMAAC and prepared superabsorbent polymers were characterized. The optimal conditions for synthesizing polyampholyte polymers with the highest swelling ratio was identified by examining the equilibrium swelling ratio of the polymer prepared under different conditions. Moreover, the unique volume phase transition properties of these polyampholyte superabsorbent polymers were studied. The effects of pH, ionic strength and the ratio of alcohol/water mixture solution on the water absorbency of the polymers were determined.

In situ quartz crystal microbalance monitoring of the adsorption of polyoxometalate on a polyampholyte polymer matrix

Hybridization of polyoxometalates (POMs) via an organic–inorganic association constitutes a new route to develop heterogeneous POM catalysts with tunable supramolecular architecture. As the structural stability of POMs is strongly influenced by the pH conditions, a quantitative understanding of the POMs-polymer association is important in practical applications. Herein, we use Quartz Crystal Microbalance (QCM) to systematically investigate the interactions of Keggin phosphotungstic acid POM with a polyampholyte polymer-coated QCM sensor as a function of pH. The mass of adsorbed POMs increases when pH decreases from 5.6 to 2, indicating that electrostatic forces play a major role in the formation of POM-polymer hybrids. This finding is complemented by AFM images that show an increase in the size of the hybrid entities from 5 to 12nm as the pH decreases from 5.6 to 2. The POM adsorbed amount at a particular pH value reaches an equilibrium level with time. The hybrids further gain in adsorbed mass only when lowering the pH value of the POM solution. The hybrid structure formed above pH 2 shows resistance to leaching as indicated by the steady level of the adsorbed mass during a rinsing step with water. However, at pH 2, the rinsing step causes desorption of some weakly adsorbed POMs. It is shown that leached POMs can be re-adsorbed back into the polymer matrix during a second contact with a POM solution at pH 2. This adsorption–desorption cycles of POMs were successfully repeated. Our experiments shed light into the coexistence of tightly as well as loosely bound POMs in hybrid catalyst formed at pH 2. The loosely bound POMs can potentially act as homogeneous catalysts when desorbed. However, these leached POMs can be re-adsorbed back into the matrix, preserving the heterogeneous state of the catalyst. Our results show that QCM is a powerful technique to study in situ the dynamics of the adsorption of POMs on a polymer matrix under different pH conditions.

010 The control of ice nucleation and growth in tissues and organs

Vitrification is a promising general approach to cryopreservation of clinically relevant tissues and organs that are sensitive to ice formation. However, the vitrification of larger samples requires cryoprotectant concentrations sufficiently high to avoid ice formation at relatively low cooling and warming rates. In an effort to avoid the toxicity that usually accompanies higher concentrations, certain extracellular additives have been identified that can improve vitrification tendency while minimizing toxicity, not just in solution but also in whole tissues and organs. Such additives act either through interaction with water in bulk solution (a class we call specialty cryoprotectants) or through apparently specific interactions with ice-like surfaces (a class we call ice blockers). Ice blockers act either through binding to ice nucleators (anti-nucleators) or by binding directly to ice (ice growth inhibitors, whose apparent generalized nucleation inhibition effect is a side effect of ice crystal binding). Unlike specialty cryoprotectants, ice blockers, presumably due to their specificity, tend to be active even at low concentrations (e.g., 0.1% w/v or less), and this property is strong evidence that a compound is an ice blocker rather than a specialty cryoprotectant. Antifreeze proteins are the prototypical and most well-known ice-active ice blockers, but their high cost and other potential disadvantages have stimulated interest in smaller non-protein alternatives. Certain flavonol glycosides and the polymer polyglycerol (PGL) are nucleation inhibitors that are active at low concentrations. More recently polyampholyte polymers with a 65% carboxylate mole fraction and polyglycidol block copolymers have been shown to have ice blocking activity. Polyvinyl alcohol (PVA), originally thought to be only a nucleation inhibitor, has since been shown in the literature to exhibit recrystallization inhibition, thermal hysteresis, and altered ice crystal morphology in its thermal hysteresis zone, all characteristics previously only observed for antifreeze proteins. PVA also raises the homogeneous nucleation temperature of water in emulsions, a behavior consistent with a structural match to ice at nanometer scales. Molecular dynamics simulations retrospectively showed that a minimum energy conformation of PVA can bind to the basal plane of ice, with hydrophobic methylene groups positioned to intercalate between water molecules in the basal plane. Zirconium acetate, which also alters ice crystal morphology and inhibits recrystallization, was also proposed to be active through bonding to the ice lattice. The diequatorial conformation of cis-1,3-cyclohexandiol (CHD) has also generated interest from the prospective observation that its hydroxyls are favorably positioned for binding to water molecules in the basal plane. One half molar (7.6% w/v) CHD was shown to almost double the thermal hysteresis activity of an antifreeze glycoprotein compared to no effect using 1,4-cyclohexanediol as a control, and 6% w/v CHD added to a vitrification solution also greatly slowed the growth of ice compared to 6% sucrose. However, some conventional solutes such as glycerol and propylene glycol can have similar effects, and the need for multi-percent concentrations is typical for a specialty cryoprotectant. In conclusion, ice blockers and specialty cryoprotectants are becoming increasingly indispensable and increasingly interesting additives for large-scale cryopreservation by vitrification. Source of funding: Supported by 21st Century Medicine, Inc. Conflict of interest: 21st Century Medicine is a supplier of PGL and PVA ice blockers. gfahy@21cm.com

Recent biomedical advances with polyampholyte polymers

ABSTRACTPolyampholyte polymer systems are composed of varying mixtures of charged monomer subunits. These polymeric systems have gained increasing attention because it is possible to design the final material properties through careful selection of the charged monomer subunits and controlling the polymer architecture. Characteristics that have been manipulated include the hydration, mechanical properties, pH responsive swelling, temperature responsive swelling, resistance to nonspecific protein adsorption, and protein conjugation capability. This had led researchers to propose the use of polyampholyte polymers as biosensor platforms, fouling release membranes, drug delivery vehicles, and tissue engineering scaffolds. This review is focused on advances that have been made over the last 5 years to develop polyampholyte polymers for these biomedical applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 40069.

Nonfouling polyampholyte polymer brushes with protein conjugation capacity

The elimination of nonspecific protein adsorption is an important challenge in many biomaterial applications. To address this issue, numerous nonfouling chemistries have been investigated. This work reports on the dual functional properties of a polyampholyte copolymer composed of positively charged [2-(acryloyloxy) ethyl] trimethyl ammonium chloride (TMA) and negatively charged 2-carboxy ethyl acrylate (CAA) monomers. TMA:CAA copolymers have previously been shown to have nonfouling properties, but the optimal conditions for nonfouling have not been determined. To accomplish this, the thickness of the polymer brush coating was varied by manipulating the surface-initiated atom transfer radical polymerization conditions. The nonspecific adsorption of fibrinogen and lysozyme was measured as a function of the copolymer brush thickness using a surface plasmon resonance biosensor. At the optimal thickness for nonfouling, nonspecific adsorption from 10% and 100% fetal bovine serum (FBS) was determined. The results indicate that at the optimal copolymer brush thickness, TMA:CAA polyampholyte materials have ultralow fouling characteristics even upon exposure to 100% FBS. The dual functional properties of TMA:CAA copolymers were demonstrated by conjugating fibrinogen to the copolymer brush over a range of brush thicknesses. The conjugation experiments clearly demonstrate that TMA:CAA copolymers have the capacity for protein conjugation at the optimal thickness for nonfouling. However, the conformational state of the copolymer brush chains impacts the overall conjugation capacity of the system. The results of this investigation indicate that TMA:CAA polyampholyte surfaces show promise for biosensor and biomaterial applications where their dual functional properties would be beneficial.

Stimuli-Responsive Surfaces Using Polyampholyte Polymer Brushes Prepared via Atom Transfer Radical Polymerization

The synthesis of AB diblock copolymer polyampholyte polymer brushes of the type Si/SiO2//poly(acrylic acid-b-vinyl pyridine) prepared using atom transfer radical polymerization is reported. Both 2- and 4-vinyl pyridine have been used. The diblock polyampholyte polymer brushes demonstrate stimuli-responsive behavior with respect to pH, showing both polyelectrolyte and polyampholyte effects. Furthermore, we have quaternized the 4-vinyl pyridine segments to form a mixed weak/strong, or annealed/quenched, polyelectrolyte system. The quaternized polymer brush exhibits different pH-responsive behavior, with decreasing film thickness being observed with increasing pH.

Stimuli-Responsive Polyelectrolyte Polymer Brushes Prepared via Atom-Transfer Radical Polymerization

We present an account of our research into polyelectrolyte polymer brushes that are capable of acting as stimuli-responsive films. We first detail the synthesis of poly(acrylic acid) polymer brushes using ATRP in a "grafting from" strategy. Significantly, we employed a chemical-free deprotection step that should leave the anchoring ester groups intact. We have demonstrated how these polymer assemblies respond to stimuli such as pH and electrolyte concentration. We have used poly(acrylic acid) polymer brushes for the synthesis of metallic nanoparticles and review this work. We have used XPS, ATR-FTIR, and AFM spectroscopy to show the presence of silver and palladium nanoparticles within polymer brushes. Finally, we report the synthesis of AB diblock polyampholyte polymer brushes that represent an extension of polyelectrolyte polymer brushes.

Theory of polyampholyte solutions

We consider polyampholyte polymers containing both positive and negative monomers randomly dispersed along the chain. Neutral chains collapse into a globule due to attractive electrostatic interactions. The behavior of the charges inside the globule is similar to that of charges in a small volume of simple electrolyte. A screening length κ−1p coming from the polymeric charge may be defined as in Debye–Hückel theory. The internal structure of the globule is that of close packed blobs of radius equal to the screening length. When salt is added this further screens the interactions and reduces the attractions. The globule begins to increase in size when the concentration of salt becomes larger than the concentration of charge on the polymer itself. Screened Coulomb interactions in a neutral chain behave like a negative contribution to excluded volume. For a chain in a good solvent there is a θ salt concentration at which the net excluded volume becomes zero. Chains are swollen above this concentration of salt, and collapsed below this concentration. For small sections of chain the Coulomb interactions are unscreened and cannot be treated as a modification to excluded volume. Chains with a strong net charge of one sign tend to behave as conventional polyelectrolyte with charges of only one sign. We determine the criterion for the value of the net charge at which the repulsions (polyelectrolyte effect) begin to dominate the attractions (polyampholyte effect). The predictions are found to be in good qualitative agreement with experiments.