Recent Advances in the Study of Synthetic Polyampholytes in Solutions

RAFT copolymerization of oppositely charged monomers and its use to tailor the composition of nonfouling polyampholytes with an UCST behaviour

The RAFT copolymerization of oppositely-charged monomers is studied to optimize the composition of polyampholytes with an UCST behaviour and nonfouling properties.

Superior Bioinert Capability of Zwitterionic Poly(4-vinylpyridine propylsulfobetaine) Withstanding Clinical Sterilization for Extended Medical Applications

The field of bioinert materials is relatively mature, as unique molecular designs for antifouling have been regularly presented over the past 30 years. However, the effect of steam sterilization, a common procedure in hospitals for sterilizing biomedical devices in clinical uses, on the stability of antifouling and hemocompatible biomaterials remains unexplored. The only available set of data indicates that poly(sulfobetaine methacrylate) (SBMA) is unstable and loses its antifouling properties when exposed to hot humid air, depriving it of its attractiveness. Here, we present zwitterionic biomaterial gels of poly(4-vinylpyridine propylsulfobetaine) (4VPPS) and explore their propensity to biofouling before and after a 1 h steam sterilization at 121 °C. After incubation with erythrocytes, leukocytes, thrombocytes, whole blood, or various bacteria ( Escherichia coli, Stenotrophomonas maltophilia), the antifouling properties of unsterilized 4VPPS gels are comparable to those of SBMA gels. Importantly, they are maintained after steam sterilization, unlike those of SBMA gels, which shows that the structure of 4VPPS and the interactions with water remain unaffected by the humid heat treatment. The antifouling properties of gels coated on materials mimicking surfaces used in biomedical devices including stainless steel (surgical knife), silicon (biochips), or titanium (electrocautery pen) are also maintained after similar sterilization. In addition, repeated sterilizations do not affect the antifouling properties of 4VPPS. Therefore, these results provide a substantial advance over the current knowledge on antifouling materials for repeated usage in actual conditions that often involve, in a biomedical environment, steam sterilization.

Design and Study of a Novel Thermal-Resistant and Shear-Stable Amphoteric Polyacrylamide in High-Salinity Solution

Abstract: Water-soluble polymers are widely used in oilfields. The rheological behaviors of these polymers in high-salinity solution are very important for stimulation of high-salinity reservoirs. In this work, a novel thermal-resistant and shear-stable amphoteric polyacrylamide (PASD), prepared from acrylamide (AM), sodium styrene sulfonate (SSS), and acryloxyethyl trimethylammonium chloride (DAC) monomers, was prepared by free-radical polymerization in high-salinity solution. The amphoteric polyacrylamide was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance spectroscopy (¹H NMR), elemental analysis, thermogravimetric analysis (TG), and scanning electron microscopy (SEM). The amphoteric polyacrylamide exhibited excellent salinity tolerance. The slow increase in apparent viscosity of the polymer with increase in salinity was interesting. The amphoteric polyacrylamide showed perfect temperature resistance in high-salinity solution. The viscosity retention reached 38.9% at 120 °C and was restored to 87.8% of its initial viscosity when temperature was decreased to room temperature. The retention ratio of apparent viscosity reached 49.7% at 170 s^-1 and could still retain it at 25.8% at 1000 s^-1. All these results demonstrated that PASD had excellent thermal-resistance and shear-stability in high-salinity solution. We expect that this work could provide a new strategy to design polymers with excellent salinity-tolerance, thermal-resistance, and shear-stability performances.

Design of a C-b-(A-co-B)-b-C telechelic polyampholyte pH-responsive gelator

We report the synthesis and the pH dependent structural and rheological properties of a telechelic polyampholyte associative polymer, composed of a random polyampholyte central block, end-capped by shorter hydrophobic blocks [C-b-(A-co-B)-b-C block/random terpolymer type].

Highly repeatable kinetically-independent synthesis of one- and two-dimensional silver nanostructures by oriented attachment

A repeatable and fast synthesis of one- and two-dimensional silver nanostructures with thickness of 20–25 nm, constructed from highly stable hexagonal and triangular nanoplates has been achieved.

A zwitterionic polymer as a novel inhibitor of protein aggregation

A zwitterionic polymer was synthesized via RAFT polymerization. This polymer prevented heat induced protein aggregation, by preventing hydrophobic interactions between protein chains in solution, thus acting as a molecular shield.

Hybrid polymeric systems bearing bulky derivatives of tris(trimethylsilyl)methane

Versatile polymeric systems based on bulky tris(trimethylsilyl)methane derivatives exhibit interesting physiochemical properties (increased chain rigidity and thermostability) and broad applicability.

Physical hydrogels composed of polyampholytes demonstrate high toughness and viscoelasticity

Hydrogels attract great attention as biomaterials as a result of their soft and wet nature, similar to that of biological tissues. Recent inventions of several tough hydrogels show their potential as structural biomaterials, such as cartilage. Any given application, however, requires a combination of mechanical properties including stiffness, strength, toughness, damping, fatigue resistance and self-healing, along with biocompatibility. This combination is rarely realized. Here, we report that polyampholytes, polymers bearing randomly dispersed cationic and anionic repeat groups, form tough and viscoelastic hydrogels with multiple mechanical properties. The randomness makes ionic bonds of a wide distribution of strength. The strong bonds serve as permanent crosslinks, imparting elasticity, whereas the weak bonds reversibly break and re-form, dissipating energy. These physical hydrogels of supramolecular structure can be tuned to change multiple mechanical properties over wide ranges by using diverse ionic combinations. This polyampholyte approach is synthetically simple and dramatically increases the choice of tough hydrogels for applications.

Polyampholyte/surfactant complexes at the water-air interface: a surface tension study

The present paper is related to interactions between strongly alternating polyampholytes, i.e., copolymers of N,N'-diallyl-N,N'-dimethylammonium chloride and maleamic acid derivatives, varying in hydrophobicity and excess charges and the oppositely charged anionic surfactant sodium dodecyl sulfate (SDS). Surface tension measurements have revealed a complex behavior with the formation of polyampholyte-SDS complexes at water-air interfaces which depends on both the hydrophobic character of the polyampholyte and electrostatic attractive forces between the polyampholyte and the anionic surfactant in dependence on pH. Hereby, maleamic acid copolymers with additional carboxylic groups in the phenylic side chain show a significant lower surface tension at the critical association concentration (CAC) due to the formation of surface-active SDS complexes and multicomplexes. In the presence of only one carboxylic group in the p-position the CAC can be strongly shifted by varying the pH due to repulsive electrostatic interactions.

Electrochemical switching of conformation of random polyampholyte brushes grafted onto polypyrrole

We demonstrate the possibilities for subtle control over redox-driven surface switching that could be obtained by altering the balance between hydrophobic, ionic, and dipolar components of polymer brushes that are grafted onto electrochemically active conducting polymers (ECP). We extend our previous work on the conformation switching of polyzwitterionic brushes grafted onto ECP to the case of ABC random polyampholyte brushes: here, a statistical near-neutral copolymer of methyl methacrylate (MMA), methacryloxyethyltrimethylammonium chloride (METAC), and 3-sulfopropyl methacrylate potassium salt (SPMA). The statistical polyampholyte differs from the polyzwitterion in that it is not strictly neutral and the charges do not have a defined spatial relationship to one another. The consequence is a significant change in the switching behavior that is also dependent on the salt concentration in the electrolyte. The results can be understood by reference to the theory of polyampholyte conformation in solution given by Higgs and Joanny modified to apply to a surface-bound brush. Three states of the polyampholyte brush are deduced from electrochemical impedance spectroscopy (EIS): collapsed, partially collapsed, and expanded. At low salt concentration, the behavior was the opposite of that of the polyzwitterion: the brush switched between partially collapsed with the ECP reduced and expanded with the ECP oxidized. With increase of salt concentration, the switch changed, to collapsed with the ECP oxidized and partially collapsed with ECP reduced. At still higher salt concentration, the switch changed back again, to partially collapsed with the ECP reduced and expanded with the ECP oxidized. Measurements of surface wetting under electrochemical control supported the interpretation. The behavior can be contrasted with that of zwitterionic brushes, which show a switch between collapsed with ECP oxidized and expanded with ECP reduced, independent of salt concentration over the same range (10(-3)-2 M NaCl) as that studied here, and that of zwitterionic-hydrophobic block copolymers where the switch is suppressed at low salt concentration. The results illustrate the significant range of behavior that can be engineered into these electrochemically switchable systems.

Anion effects on anti-microbial activity of poly[1-vinyl-3-(2-sulfoethyl imidazolium betaine)]

Recent investigations in the anti-microbial properties of the functional polymers are predominantly focused on the structure of the cationic moieties. In the present study, we investigated that the nature of the anion present in polysulfobetaines affects activity against certain microorganisms and their anti-microbial properties have been rationalized in terms of the structure-activity relationship. Vinyl imidazolium-based polysulfobetaines were prepared by the quaternization of poly(N-vinyl imidazole) with sodium salt of 2-bromo ethanesulfonic acid. The bromide counter anion of the resulting polymer was exchanged with different anions to generate a series of polymers. These were characterized by FTIR, DSC, XRD, SEM, elemental analysis (C, H, N and S) and viscosity measurements. The anti-microbial activity studies were carried against three fungi (Aspergillus niger, Byssochlamys fulva and Mucor circenelliods) and two bacteria (Bacillus coagulans BTS-3 and Pseudomonas aeruginosa BTS-2). The nature of the anion affects the structure of polysulfobetaine by realignment of polymer chains. The anion-dependent anti-microbial properties of polysulfobetaines result from the interaction of the microbes at the polymer interface.

Synthesis, characterization, and DNA adsorption studies of ampholytic model conetworks based on cross-linked star copolymers

Five model conetworks based on cross-linked star ampholytic copolymers were synthesized by group transfer polymerization. The ampholytic copolymers were based on two hydrophilic monomers: the positively ionizable 2-(dimethylamino)ethyl methacrylate (DMAEMA) and the negatively ionizable methacrylic acid (MAA). Ethylene glycol dimethacrylate was used as the cross-linker. These five ampholytic model conetworks were isomers based on equimolar DMAEMA-MAA copolymer stars of different architectures: heteroarm (two), star block (two), and statistical. The two networks based on the homopolymer stars were also synthesized. The MAA units were introduced via the polymerization of tetrahydropyranyl methacrylate and the acid hydrolysis of the latter after network formation. All the precursors to the (co)networks were characterized in terms of their molecular weights using gel permeation chromatography (GPC). The mass of the extractables from the (co)networks was measured and characterized in terms of molecular weight and composition using GPC and proton nuclear magnetic resonance (1H NMR) spectroscopy, respectively. The degrees of swelling (DS) of all the ampholytic conetworks were measured as a function of pH and were found to present a minimum at a pH value which was taken as the isoelectric point, pI. The DS and the pI values did not present a dependence on conetwork architecture. Finally, DNA adsorption studies onto the ampholyte conetworks indicated that DNA binding was governed by electrostatics.