Aqueous Acrylamide Research Articles

A flexible, autonomous self-healing and high ionic conductivity hydrogel electrolyte for all-in-one supercapacitor

Conventional polyvinyl alcohol-based gel electrolytes are generally limited in ionic conductivity and cannot well meet the requirements of the self-healing and flexible smart device. Herein, we design a highly conductive hydrogel electrolyte (ionic conductivity up to 84 mS cm−1), based on cross-linked aqueous acrylamide (AAm) solution in the presence of poly(N-vinylpyrrolidone) (PVP), with excellent self-healing capability by intermolecular hydrogen bonds between PVP and PAM. The self-healing all-in-one flexible supercapacitor fabrication with the gel electrolyte and in-situ polymerization polypyrrole (PPy) electrode can achieve repeated healable 5 cycles without extra addition, stretch up to 750 % compared with the original lengths and bend different angles with slight performance decay. This work provides new idea for the synthesis of highly conductive, self-healing and flexible hydrogel electrolyte to promote the development of all-in-one supercapacitor with high specific capacitance for practical applications in flexible and wearable electronics.

Textured and Hierarchically Constructed Polymer Micro- and Nanoparticles

Microfluidic techniques allow for the tailored construction of specific microparticles, which are becoming increasingly interesting and relevant. Here, using a microfluidic hole-plate-device and thermal-initiated free radical polymerization, submicrometer polymer particles with a highly textured surface were synthesized. Two types of monomers were applied: (1) methylmethacrylate (MMA) combined with crosslinkers and (2) divinylbenzene (DVB). Surface texture and morphology can be influenced by a series of parameters such as the monomer–crosslinker–solvent composition, surfactants, and additives. Generally, the most structured surfaces with the simultaneously most uniform particles were obtained in the DVB–toluene–nonionic-tensides system. In a second approach, poly-MMA (PMMA) particles were used to build aggregates with bigger polymer particles. For this purpose, tripropyleneglycolediacrylate (TPGDA) particles were synthesized in a microfluidic co-flow arrangement and polymerized by light- irradiation. Then, PMMA particles were assembled at their surface. In a third step, these composites were dispersed in an aqueous acrylamide–methylenebisacrylamide solution, which again was run through a co-flow-device and photopolymerized. As such, entities consisting of particles of three different size ranges—typically 0.7/30/600 µm—were obtained. The particles synthesized by both approaches are potentially suitable for loading with or incorporation of analytic probes or catalysts such as dyes or metals.

Transmittance enhancement of La0.4Gd1.6Zr2O7 transparent ceramic by aqueous AM gel-casting with pretreated powder

Via a powder pretreatment process, transparent La0.4Gd1.6Zr2O7 ceramics were successfully fabricated through the aqueous AM (acrylamide) gel-casting technique. Our research shows that the water absorption of La2O3 has significant influence on the viscosity of slurry, leading to low density of the green body and poor transparency of ceramic. By pretreating the mixed powder via a solid-state reaction, the viscosity and pH results have shown that the single-phase pretreated powder has a positive improvement on the gel-casting process. Compared with the mixed powder, the pretreating method has effectively improved the slurry with higher solid content and lower viscosity. Therefore, the pretreated powder combined with gel-casting method have a positive influence on the density of green body and the optical quality of obtained La0.4Gd1.6Zr2O7 ceramics. The polished ceramics with 40 mm in diameter (Ø = 40 mm) and 1.5 mm in thickness (δ = 1.5 mm) exhibited the in-line transmittance of 78% at 1100 nm and a maximum transmittance of about 80% in the infrared region, as well as a wide range of high stable transmittance among 0.6–6.0 µm wavelength. Our work opens a way for highly transparent ceramic preparation by aqueous AM gelling system with hygroscopic rare earth oxide as raw materials.

Additive manufacturing of silica ceramics from aqueous acrylamide based suspension

The UV curable acrylamide-based suspension is an environmental material used for digital light processing (DLP) which is currently one of the most accurate additive manufacturing methods. In this paper, a high loaded and low viscosity silica suspension was developed based on acrylamide system, moreover, the influence of dispersant, solid loading and ball milling time on the rheological properties of silica suspensions was investigated. Furthermore, in order to understand the polymerization reaction process, the effect of photoinitiator concentration and ratio between monomer (AM) and the cross-linking agent (MBAM) on curing properties of silica suspension was discussed. Finally, following the study of rheological properties and curing characteristics, the testing results of sintered silica ceramics showed a density and flexural strength of 1.42 g/cm3 and 13.31 MPa at 1200 °C respectively.

Static Light Scattering Monitoring and Kinetic Modeling of Polyacrylamide Hydrogel Synthesis

A kinetic model describing aqueous acrylamide homopolymerization and copolymerization of acrylamide with methylene bisacrylamide, leading to hydrogel formation, is presented and applied in the simulation of these reaction processes. This modeling approach is based on population balances of generating functions and, besides the crosslinking mechanisms inherent to network formation, other specific kinetic steps important in acrylamide polymerization (e.g., branching due to backbiting) are considered in the simulation tool developed. The synthesis of acrylamide polymers and hydrogels was performed at 26 °C and at 40 °C using two different initiation systems. The formation of such materials was monitored using in-line static light scattering (SLS), and the spatial inhomogeneity of the final hydrogels was also measured using this experimental technique. It is shown that the simulations are helpful in describing information provided by SLS in-line monitoring, namely in the early stages of polymerization with the transition from dilute to semi-dilute regime. Indeed, it finds a plausible match between the critical overlap polymer concentration and gelation, this later leading to the observed spatial heterogeneity of the hydrogels. Usefulness of the kinetic model for defining operation conditions (initial composition, semi-batch feed policies, chain transfer, etc.) in making the shift from gelation to the semi-dilute regime is discussed, and the extension of this approach to processes enabling a higher control of gelation (e.g., controlled radical polymerization) is also prospected.

CFD population balance modeling and dimensionless group analysis of a multiphase oscillatory baffled column (OBC) using moving overset meshes

This paper presents a CFD model and hydrodynamic study of a moving-baffle oscillatory baffled column (moving-baffle OBC). This work marks the first instance that moving overset meshing was used to simulate agitator motion in a fluid system. Population balance results are validated with experimental data for the inverse-suspension of non-reactive aqueous acrylamide in Isopar oil. A comparison of the droplet size distributions produced via various multiphase simulation methods was performed, resulting in a better overall agreement with the experimental literature for simulations applying the volume of fluid (VOF) multiphase method. Hydrodynamic studies reveal patterns of local flow circulations and centermost axial currents in relation to agitator position. Examination of the dimensionless groups traditionally used to describe flow conditions for moving-baffle OBCs reveal a considerable discrepancy between the previously-defined oscillatory Reynolds number and oscillatory Strouhal number with numbers derived from fluid flow within the column. A numerical correction has been presented to illustrate the nonlinear effect of oscillation amplitude on fluid flow through the system and to provide a more realistic estimation of the Reynolds number and Strouhal number for the modeled moving-baffle OBC.

Unprecedented Acid-Promoted Polymerization and Gelation of Acrylamide: A Serendipitous Discovery.

Dilute acid polymerizes degassed, aqueous acrylamide with concomitant gelation, without the need for added free radical initiator or cross-linking agent. This reaction is accelerated by sonication or UV irradiation, but inhibited by adventitious oxygen or the addition of a free radical inhibitor, suggesting an acid-accelerated free radical process. The resulting hydrogels are thixotropic in nature and partially disrupted by the addition of chaotropic agents, indicating the importance of hydrogen bonding to the 3D network. This discovery was made while trying to prepare pectin-polyacrylamide hydrogels. We observed that pectin initiated the gelation of acrylamide, but only if the aqueous pectin samples had a pH lower than ca. 5.

Frozen Acrylamide Gels as Dynamic Nuclear Polarization Matrices.

Aqueous acrylamide gels can be used to provide dynamic nuclear polarization (DNP) NMR signal enhancements of around 200 at 9.4 T and 100 K. The enhancements are shown to increase with crosslinker concentration and low concentrations of the AMUPol biradical. This DNP matrix can be used in situations where conventional incipient wetness methods fail, such as to obtain DNP surface enhanced NMR spectra from inorganic nanoparticles. In particular, we obtain 113 Cd spectra from CdTe-COOH NPs in minutes. The spectra clearly indicate a highly disordered cadmium-rich surface.

Facile synthesis of gold nanoparticles in aqueous acrylamide solution

A method is advanced for preparing gold nanoparticles (NPs) at 50°C in aqueous acrylamide (AAm), which has the dual function of a reducing agent for HAuCl4 and a protective ligand for NPs. Nanoparticles have gold cores with the average size d Au = 20.9 ± 3.6 nm. The growth kinetics of NPs has been studied. Films of NPs have been produced on glass, silica, silicon, and polyethylene terephthalate (PET) substrates. The NPs and films have been characterized by UV-Vis and IR spectroscopy, X-ray powder diffraction, transmission and scanning electron microscopy, and atomic-force microscopy.

High molecular weight polyacrylamide nanoparticles prepared by inverse emulsion polymerization: reaction conditions-properties relationships

High molecular weight polyacrylamide (PAM) nanoparticle dispersions are products with wide application possibilities, the most important of which is in petroleum industry such as drilling fluid and flooding agent in enhanced oil recovery. For that aim, it is necessary to achieve complete control of the final dispersion and polymer properties during the synthesis step. In this work, PAMs were synthesized by inverse emulsion polymerization of aqueous acrylamide solution in cyclohexane in the presence of emulsifier mixture of Span 20 and Span 80. We present a comprehensive study of the effects of variation of all important reaction conditions (agitation rate, reaction time and temperature, initiator type and concentration, emulsifier HLB ratio and its concentration, and water to oil ratio) on final monomer conversion, reaction kinetics, polymer intrinsic viscosity and molecular weight, particle size and distribution, and colloidal stability. Finally, the relationships between the reaction conditions and the polymer properties were developed, which allowed determination of the ranges of variation of reaction conditions for optimal PAM properties for the oil industry applications: high molecular weight and intrinsic viscosity, nanosized polymer particles with narrow particle size distribution, and improved colloidal stability of the final dispersions.

Can r-graphene oxide replace the noble metals in SERS studies: the detection of acrylamide

Environmental context The need for detecting and sensing hazardous materials that can contaminate our food and water is growing each and every year. Regulation of these contaminants to safeguard human health depends on the ability to detect them at ultra-low concentrations in the environment. This work proposes a simple and efficient substrate preparation for detecting acrylamide, a toxic and carcinogenic material usually found in drinking water. Abstract Polyacrylamide acts as a very common water purifier worldwide. Unfortunately, it leaves hazardous and toxic residues of its monomer, acrylamide (C3H5NO), in water sources. The World Health Organization (WHO), the Food and Agriculture Organisation of the United Nations (FAO) and the European Union (EU) set the maximum contaminant level of acrylamide in drinking water to 0.1–0.5µgL–1. This environmental risk encouraged our efforts to develop surface-enhanced Raman spectroscopy (SERS) probes that are easy and simple to fabricate, and also have superb detection ability. We report down to 0.071µgL–1 acrylamide detection with good reproducibility, which is even lower than the WHO, FAO and EU requirements, and may be used as a powerful analytical alternative for detection. In this manuscript, we present a practical route to fabricate these detection substrates for detection of ultra-low concentrations of aqueous acrylamide solutions. The facile method is based on deposition of graphene oxide on Si wafers by ultrasonication, followed by surface reduction. These substrates require no adhesion layer or pretreatment with O2 plasma or aminopropyl triethoxysilane for the coating process. Sonochemical deposition of silver nanoparticles on the substrates is also carried out and the product compared with the proposed Si–reduced graphene oxide wafers.

Preparation of poly(acrylamide)/nanoclay organic-inorganic hybrid nanoparticles with average size of ∼250 nm via inverse Pickering emulsion polymerization

In this study, the preparation of poly(acrylamide)/nanoclay organic-inorganic hybrid nanoparticles via surfactant-free inverse emulsion polymerization by using organically modified clay platelets as stabilizers was discussed. Colloidally stable inverse Pickering emulsions of aqueous acrylamide solution in cyclohexane (solvent) stabilized by hydrophobic Cloisite 20A (MMT20) were prepared. Polymerization was carried out via 2,2′-azobis(isobutyronitrile) and composite particles with an average size of ∼250 nm were obtained. The effect of initiator and solvent type on the stability, size, size distribution, and morphology of the produced composite particles was examined. It was observed that in the presence of xylene as solvent, particles with bigger sizes and broader size distribution were obtained. Furthermore, using an ionic initiator resulted in a slight coagulation during polymerization and smaller particles. Moreover, the effect of various polymerization conditions such as temperature, initiator, and crosslinking agent concentration and clay content on the polymerization rate was evaluated. The experimental results showed that polymerization rate increases with an increase in polymerization temperature, crosslinking agent concentration, and initiator content. However, increasing in clay content results in a lower polymerization rate.

Facile Fabrication of Tough Hydrogels Physically Cross-Linked by Strong Cooperative Hydrogen Bonding

Novel hydrogels with excellent mechanical properties have prompted applications in biomedical and other fields. The reported tough hydrogels are usually fabricated by complicated chemical and/or physical methods. To develop more facile fabrication methods is very important for the practical applications of tough hydrogels. We report a very simple yet novel method for fabricating tough hydrogels that are totally physically cross-linked by cooperative hydrogen bonding between a pre-existing polymer and an in situ polymerized polymer. In this work, tough hydrogels are prepared by heating aqueous acrylamide (AAm) solution in the presence of poly(N-vinylpyrrolidone) (PVP) but without any chemical initiators or covalent bonding cross-linking agents. Mechanical tests of the as-prepared and swollen PVP-in situ-PAAm hydrogels show that they exhibit very high tensile strengths, high tensile extensibility, high compressive strengths, and low moduli. Comparative synthesis experiments, DSC characterization, and molecular modeling indicate that the formation of strong cooperative hydrogen bonding between the pre-existing PVP and the in situ formed PAAm chains contributes to the gel formation and the toughening of the hydrogels. The unique microstructure of the gels with evenly distributed flexible cross-linking sites and long polymer chains attached to them endow the hydrogels with an excellent mechanism of distributing the applied load.

Synthesis and Characterization of Temperature-Sensitive Poly(N-isopropylacryamide-co-acrylamide)/Montmorillonite Nanocomposite Hydrogels

This paper reports a temperature-sensitive poly(N-isopropylacryamide-co-acrylamide)/montmorillonite (P(NIPAAm-co-Am)/MMT) nanocomposite hydrogel with enhanced mechanical properties and thermodynamic stability based on chitosan and nanoparticle MMT. With biodegradable N-maleyl chitosan crosslinker, the temperature-sensitive nanocomposite hydrogel was prepared by free radical polymerization in aqueous solution, using N-isopropylacryamide (NIPAAm), acrylamide (Am), and montmorillonite (MMT) as materials. The clay content varied from 0 to 7 wt% (based on the monomer). The temperature-sensitive behavior, mechanical property, thermodynamic stability, and enzymatic degradation of the nanocomposite hydrogels were investigated in detail.

Micro continuous flow-through synthesis of triangular silver nanoprisms and their incorporation in complexly composed polymer microparticles

The micro fluid segment technique is used for the continuous-flow synthesis for small silver nanoparticles by reduction of silver ions with sodium borohydride in aqueous solution and for the growth of triangular silver nanoprisms. In result, triangular nanoprisms are obtained in very high yield and high homogeneity. The tuning of the in-plane dipole plasmon resonance can easily be controlled by choosing suited flow rate ratios of silver salt solution and colloidal solution of seed nanoparticles or by different silver salt concentrations. The colloidal aqueous solutions of metal nanoparticles can be used for the preparation of mixtures with water-soluble monomers as acrylamide and for the formation of hydrogel-polymer composite particles in a droplet-based photopolymerization process. Beside spherical composite particles, Janus particles with a hydrophilic nanoparticle-containing composite part are prepared by a combined photopolymerization of the aqueous acrylamide reaction mixture together with embedded droplets of an acrylate-based monomer (Tripropylene Glycol Diacrylate, TPGDA) mixture in a micro co-flow twin arrangement. The components of the mushroom-like particles can easily be distinguished by optical microscopy due to their light-scattering and fluorescence behavior.

Fluorescent polyacrylamide nanoparticles for naproxen recognition

We present the synthesis of fluorescent acrylamide nanoparticles (FANs) capable of recognizing non-steroidal anti-inflammatory drugs (NSAIDs) in buffered aqueous solutions. Within this important group, we selected naproxen, one of the 2-arylpropionic acids (profens), due to its use for the treatment of moderate pain, fever, and inflammation. The nanosensors were prepared under mild conditions of inverse microemulsion polymerization using aqueous acrylamide as the monomer and N,N'-methylenebisacrylamide as the cross-linker, employing the surfactants polyoxyethylene-4-lauryl ether (Brij 30) and sodium bis(2-ethylhexyl)sulfosuccinate in hexane. Furthermore, a fluorescent monomer, (E)-4-[4-(dimethylamino)styryl]-1-[4-(methacryloyloxymethyl)benzyl]pyridinium chloride (mDMASP) has been synthesized and incorporated into the nanoparticles. The nanosensors exhibit a broad absorbance at around 460 nm and a structureless fluorescence band with maximum at 590 nm in 0.5 M phosphate buffer (pH = 7.2). The recognition process is performed on the basis of ionic interactions which are monitored by the fluorescence increase at 590 nm upon addition of different concentrations of naproxen. The FANs show a size distribution in the range of 20-80 nm, with a hydrodynamic diameter of 34 nm. In order to assess the selectivity of the FANs, a systematic study was conducted on the effect produced by drugs and biomolecules that could interfere with the analysis of naproxen.

Validation by collaborative trial of an isotope dilution liquid chromatographic tandem mass spectrometric method to determine the content of acrylamide in roasted coffee

A method for the determination of acrylamide in roasted coffee was subjected to method validation by collaborative trial. The aim was to extend the scope of a method already standardized for the determination of acrylamide in bakery and potato products to include roasted coffee. Modifications of the already standardized method were therefore kept to a minimum. The method was based on aqueous extraction of the roasted coffee matrix and solid-phase extraction (SPE) clean-up followed by isotope dilution high-performance liquid chromatography with tandem mass spectrometric detection (LC-MS/MS). The test portion of the sample was spiked with stable isotope-labelled acrylamide and extracted on a mechanical shaker with n-hexane and water for 1 h. The sample extract was centrifuged, the organic phase discarded, and a portion of the aqueous extract further cleaned-up by SPE on an Isolute Multimode cartridge followed by a second clean-up step on an Isolute ENV + cartridge. The volume of the acrylamide-containing fraction eluted from the second SPE column was reduced by evaporation and analysed by LC-MS/MS. Three coffee samples and one aqueous acrylamide standard solution were sent to eleven laboratories from eight European Union Member States. All samples were sent as blind duplicates. Based on the reported results, the relative standard deviations for reproducibility (RSDR) were 11.5% at a level of 160 µg kg−1, 10.1% at a level of 263 µg kg−1, and 9.6% at a level of 585 µg kg−1. The values for repeatability (RSDr) in those materials ranged from 1.0% to 3.5%. The method performance parameters satisfied internationally accepted criteria. Hence, the method would be suitable for the enforcement of regulatory limits.

Improvement on the mechanical properties of zinc oxide green sheets by aqueous acrylamide gel tape casting

Various organic constituents were used to improve the mechanical properties of green sheets prepared by a novel aqueous gel tape casting. Two deadly problems of green sheets: brittle and surface exfoliation were settled and mechanical properties were estimated. Compared with poly(ethylene glycol) (PEG400 (Mw ≈ 400)), poly(propylene glycol) (PPG400 (Mw ≈ 400)) and di-ethylic phthalate (DEP), glycerol was the most efficient plasticizer to improve the flexibility of the green sheet. The addition of PEG2000 eliminated the surface-exfoliation phenomenon of green sheets in air and had no distinct deterioration in mechanical properties. The flexible and lubricous green sheets were obtained. The solid loading of the suspension reached 73.5 wt.% and the relative green density was 58%.

Can Peptide-Lipid Interactions Predict Bactericidal and Hemolytic Activity in Antimicrobial Peptides?

It is relatively simple to design highly amphipathic linear cationic beta-sheet peptides containing 10-to-11 amino acids that possess potent antimicrobial activity. Often, however, these peptides also are quite hemolytic, so that there is insufficient selectivity between bacterial and human cells. Peptides with little or no hemolytic (or other toxic) activity toward human cells at 100 or more times the minimum inhibitory concentrations toward bacterial cells might be potential candidates for clinical use as antimicrobials. Since these peptides typically exert their bactericidal action through membrane disruption, we are interested in how they interact with model lipid vesicles. Here, we investigated how a group of peptides all containing a single tryptophan residue interact with large unilamellar vesicles (LUV) consisting of either anionic phosphatidylglycerol (PG), neutral phosphatidylcholine (PC), mimicking a mammalian plasma membrane surface, or a 2:1 mixture of phosphatidylethanolamine (PE) and PG, mimicking an E. coli plasma membrane surface. Lipid-peptide interactions are assessed by: (1) peptide conformation using circular dichroism; (2) proteolytic degradation; and (3) quenching of tryptophan fluorescence by aqueous acrylamide and membrane-bound 10-doxyl-nonadecane. By comparing results in the absence and presence of LUV, we assessed three sets of peptides with (a) high antimicrobial and high hemolytic activity, (b) low antimicrobial and low hemolytic activity, and (c) high antimicrobial and low hemolytic activity. Our results demonstrate that the ability of these peptides to interact with LUV of defined lipid composition in most cases correlates well with their activities in bacterial and human cells.

The Trimeric Periplasmic Chaperone Skp of Escherichia coli Forms 1:1 Complexes with Outer Membrane Proteins via Hydrophobic and Electrostatic Interactions

The interactions of outer membrane proteins (OMPs) with the periplasmic chaperone Skp from Escherichia coli are not well understood. We have examined the binding of Skp to various OMPs of different origin, size, and function. These were OmpA, OmpG, and YaeT (Omp85) from Escherichia coli, the translocator domain of the autotransporter NalP from Neisseria meningitides, FomA from Fusobacterium nucleatum, and the voltage-dependent anion-selective channel, human isoform 1 (hVDAC1) from mitochondria. Binding of Skp was observed for bacterial OMPs, but neither for hVDAC1 nor for soluble bovine serum albumin. The Skp trimer formed 1:1 complexes, OMP·Skp 3, with bacterial OMPs, independent of their size or origin. The dissociation constants of these OMP·Skp 3 complexes were all in the nanomolar range, indicating that they are stable. Complexes of Skp 3 with YaeT displayed the smallest dissociation constants, complexes with NalP the largest. OMP binding to Skp 3 was pH-dependent and not observed when either Skp or OMPs were neutralized at very basic or very acidic pH. When the ionic strength was increased, the free energies of binding of Skp to OmpA or OmpG were reduced. Electrostatic interactions were therefore necessary for formation and stability of OMP·Skp 3 complexes. Light-scattering and circular dichroism experiments demonstrated that Skp 3 remained a stable trimer from pH 3 to pH 11. In the OmpA·Skp 3 complex, Skp efficiently shielded tryptophan residues of the transmembrane strands of OmpA against fluorescence quenching by aqueous acrylamide. Lipopolysaccharide (LPS), a major component of the outer membrane of Gram-negative bacteria, bound to OmpA·Skp 3 complexes at low stoichiometries. Acrylamide quenching of fluorescence indicated that in this ternary complex, the tryptophan residues of the transmembrane domain of OmpA were located closer to the surface than in binary OmpA·Skp 3 complexes. This may explain previous observations that folding of Skp-bound OmpA into lipid bilayers is facilitated in presence of LPS.