Monomer In Aqueous Solution Research Articles

Mechanical Enhancement of Bioinspired Polydopamine Nanocoatings.

Inspired by the catechol and amine-rich adhesive proteins of mussels, polydopamine (pDA) has become one of the most widely employed methods for functionalizing material surfaces, powered in part by the versatility and simplicity of pDA film deposition that takes place spontaneously on objects immersed in an alkaline aqueous solution of dopamine monomer. Despite the widespread adoption of pDA as a multifunctional coating for surface modification, it exhibits poor mechanical performance. Attempts to modify the physical properties of pDA by incorporation of oxidizing agents, cross-linkers, or carbonization of the films at ultrahigh temperatures have been reported; however, improving mechanical properties with mild post-treatments without sacrificing the functionality and versatility of pDA remains a challenge. Here, we demonstrate thermal annealing at a moderate temperature (130 °C) as a facile route to enhance mechanical robustness of pDA coatings. Chemical spectroscopy, X-ray scattering, molecular force spectroscopy, and bulk mechanical analyses indicate that monomeric and oligomeric species undergo further polymerization during thermal annealing, leading to fundamental changes in molecular and bulk mechanical behavior of pDA. Considerable improvements in scratch resistance were noted in terms of both penetration depth (32% decrease) and residual depth (74% decrease) for the annealed pDA coating, indicating the enhanced ability of the annealed coating to resist mechanical deformations. Thermal annealing resulted in significant enhancement in the intermolecular and cohesive interactions between the chains in the pDA structure, attributed to cross-linking and increased entanglements, preventing desorption and detachment of the chains from the coating. Importantly, improvements in pDA mechanical performance through thermal annealing did not compromise the ability of pDA to support secondary coating reactions as evidenced by electroless deposition of a metal film adlayer on annealed pDA.

In situ Bi2O3-loaded polypyrrole nanocomposites for carbon dioxide gas sensing

In the present work, an attempt has been made to detect carbon dioxide (CO2) using an in situ-loaded Bi2O3–polypyrrole nanocomposite sensor. The polypyrrole (PPy) was prepared by oxidative polymerization method from precursor’s monomer pyrrole and aqueous solution of ammonium persulphate. The prepared nanocomposites were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), ultraviolet–visible spectroscopy (UV–Vis), thermogravimetric–differential thermal analysis (TG–DTA) and Raman spectroscopy. Thick films of the synthesized PPy nanocomposites were deposited on glass substrate by screen printing technique. Resistive type gas sensors are extensively used in a number of modern applications such as emission control and energy efficiency. By considering this view, PPy nanocomposite films were prepared for gas sensing application. The XRD analysis revealed amorphous nature. The SEM micrograph showed that nanocomposite particles have irregular morphology and size. The nanocomposites showed a good sensing performance toward CO2 gas. The highest value of CO2 gas sensing response was shown by 25 wt% Bi2O3-loaded PPy nanocomposite sample (S5), which was found to be 0.065 for 50 ppm. Operating temperature for the optimized sample S5 toward CO2 gas was found to be 363 K. Similarly, the optimized sample S5 showed an excellent stability response against CO2 gas and atmospheric change for 30 days.

Study of Synthesis and Flocculation Properties of New Modified Hydrophobic Organic Polymer P(AM-DM-DMC12)

A new modified hydrophobic organic polymer P(AM-DM-DMC12) is synthesized by free radical polymerization of three monomers in aqueous solution using a REDOX initiator system. Its structure is characterized by FT-IR and 1H-NMR, the effect of reaction conditions on the product is studied, and the flocculation performance and mechanism are discussed with the aim of wastewater turbidity and COD removal rate. The results showed that the synthesized compounds accorded with the target structure, and the optimum synthetic conditions are as follows: the molar ratio of AM, DM, and DMC12 is 4 : 1 : 1, total mass fraction of monomer is 35%, the mass fraction of redox initiator is 0.06%, and the molecular weight of P(AM-DM-DMC12) is 1.02×107. Moreover, the flocculation effect of P(AM-DM-DMC12) is obviously better than that of PAM, and it has the advantages of short flocculation time, low dosage, and wide application range of pH and has a good industrial application value and prospect.

Photocatalysis of ZnTPyP fibers fabricated by surfactant-assisted method: Effect of surfactant and kinetic studies

We fabricated 5,10,15,20-tetra(4-pyridyl)porphyrinatozinc(II) (ZnTPyP) fibers by utilizing surfactant-assisted method with cetyltrimethylammonium bromide (CTAB). The ZnTPyP fibers became longer as molar ratio of CTAB to ZnTPyP (γ) increased. In the case of γ ≥ 50, the Soret band of ZnTPyP monomer was observed after stirring for 1 h and was split into two peaks after the aging at 40 °C for more than 5 days. On the other hand, such split peaks were observed without the aging when the γ value was 10 or 20. These findings suggest that CTAB interacts with the ZnTPyP monomer in aqueous solution to form micelles, and the fibers are gradually constructed by self-assembling the stabilized ZnTPyP monomer. Photocatalytic activity of the ZnTPyP fibers was evaluated for the degradation of rhodamine B (RhB) in water under visible light (VL) irradiation. The highest photocatalytic activity was obtained at γ = 150–300, indicating that the fibers with 1.3–2.0 μm were the most suitable as photocatalyst. When air was bubbled in the reaction solution, the photocatalytic activity was higher than that under N2 bubbling. However, absorption peak attributed to the ZnTPyP fibers decreased under air bubbling although it remained almost constant under N2 bubbling. These results suggest that the ZnTPyP fibers can act as photocatalyst and active oxygen species such as O2•− radical might decompose the ZnTPyP fibers. Kinetic studies were performed to clarify the degradation mechanism of RhB under the experimental condition where the decomposition of the ZnTPyP fibers was negligible.

Investigation of molecular and mesoscale clusters in undersaturated glycine aqueous solutions

In this work DLS, NTA, SAXS and NMR were used to investigate populations, size distributions and structure of clusters in undersaturated aqueous solutions of glycine. Molecular and colloidal scale (mesoscale) clusters with radii around 0.3-0.5 nm and 100–150 nm, respectively, were observed using complementary experimental techniques. Molecular clusters are consistent with hydrated glycine dimers present in equilibrium with glycine monomers in aqueous solutions. Mesoscale clusters previously observed in supersaturated glycine solutions appear to be indefinitely stable, in mutual equilibrium within mesostructured undersaturated solutions across all glycine concentrations investigated here, down to as low as 1 mg/g of water.

Water vapor transport properties of interfacially polymerized thin film nanocomposite membranes modified with graphene oxide and GO-TiO2 nanofillers

Graphene oxide (GO) and its composite with TiO2 (GT) were utilized as nano-filler materials to prepare highly permeable and water vapor selective nanocomposite membranes. The nano-fillers were characterized using different analytical tools to determine their physicochemical properties. Nanocomposite membranes were prepared by dispersing the nano-fillers in aqueous phase monomer solution for interfacial polymerization reaction on the inner surface of Polysulfone hollow fiber membrane. Surface morphology and bonding chemistry of the nanocomposite membrane was analyzed using various analytical tools. The two types of nano-fillers were compared for their compatibility with the polyamide matrix, and consequently, the water vapor separation performance of the resulting membrane. Results revealed that both the nano-fillers are firmly attached to the polyamide layer via hydrogen and covalent bonds. GT based membranes have higher surface roughness and better hydrophilicity as compared to GO. In addition, GT membranes have more carboxyl groups and lesser degree of cross-linking due to the interference with interfacial polymerization reaction. This leads to a higher permeance (2820 GPU) and a water vapor/nitrogen selectivity when compared to other TFN membranes reported in literature. The nano-fillers act as active sites for preferential transport of water vapor molecules through the membrane thereby, significantly improving water vapor permeance.

Tuning roughness features of thin film composite polyamide membranes for simultaneously enhanced permeability, selectivity and anti-fouling performance

Thin film composite (TFC) polyamide membranes set the golden standard for reverse osmosis technology, but tuning their permeability and selectivity remains a major challenge because of the inherent permeability-selectivity trade-off. Creating nano-sized voids within the polyamide rejection layer can tune the membrane roughness and increase its effective filtration area to improve the water permeability. Here we prepare nano-foamed polyamide rejection layers by adding sodium bicarbonate into the aqueous solution of amine monomers. We show a systematic evolution of the roughness structure of polyamide membranes, with increasingly leaf-like and belt-like features appearing under enhanced nano-foaming conditions. These nano-foamed features can result in remarkable improvements in both water permeability and salt rejection and reduce membrane fouling propensity at the same time. Our study paves a new research direction for designing future generation of desalination membranes, which holds vast potential to reduce the cost and energy consumption of desalination while achieving improved product water quality.

SYSTEMIC HEMOSTATIC AND PROTHROMBOTIC EFFECTS OF FIBRIN-MONOMER IN EXPERIMENT WITH DOSED LIVER THERAPY

Objective of the study is to experimentally evaluate system hemostatic and prothrombotic effects of intravenous fibrin monomer (FM). Materials and methods. Eighty two Chinchilla rabbits weighing 3–4 kg were used in the study. In addition to the placebo, animals were administered an aqueous solution of fibrin monomer (FM) intravenously at doses of 0.1, 0.25, 0.5, 1.0, 2.5 and 5.0 mg/kg. After 1 hour, a standard liver injury was performed and the blood loss (% of the circulating blood volume) resulting from parenchymal hemorrhage was estimated. Hemostatic system examination included platelet number in venous blood and fibrinogen and D-dimer levels in blood plasma. Results and discussion. Blood loss after dosed injury with placebo was 10.0 [4.0; 15.7] % blood volume (median [25th percentile; 75th percentile]). FM preparation doses of 0.25, 2.5 and 5.0 mg/kg resulted in a decrease of blood loss by 6.3 (p < 0.001), 7.8 (p < 0.001) and 2.7 times (p = 0.04) (1.6 [1.0; 3.0], 1.3 [0.6; 1,6] and 3.7 [2.8; 5.3] % blood volume, respectively).High doses of FM preparation (2.5 and 5.0 mg/kg) minimized blood loss due to activation of coagulation and thrombus formation, which was illustrated by a 7.0–8.0-fold increase in D-dimer level (compared to placebo). 0.25 mg/kg of FM preparation did not lead to an increase of D-dimer content, although the blood loss was greatly reduced. Conclusion. The data obtained show the presence of unique hemostatic properties in low-dose FM preparation (0.25 mg/kg), which allows creating system hemostatic agents of a new generation.

Novel Electro Polymerization Method to Synthesized Anti-corrosion Coated Layer on Stainless Steel Surface from (N-Benzothiazolyl Maleamic Acid) and Study its Biological Activity

Electro polymerization of N-benzothiazolyl maleamic acid (NBM) was carried out on stainless steel plate electrode in a protic medium of monomer aqueous solution using electrochemical oxidation procedure in electrochemical cell.Spectroscopic characterization techniques were investigated to obtain information about the chemical structure of polymer. The anti-corrosion action of polymer was investigated on stainless steel by electrochemical polarization method. In addition, the effect of adding nanomaterial (TiO2, ZnO (bulk-nano)) to monomer solution on the corrosion behavior of stainless steel was investigated. The results obtained showed that the corrosion rate of S-steel increased with temperature increase from 293K to 323K and the values of inhibition efficiency by coating polymer increase with nanomaterial addition. Apparent energies of activation have been calculated for the corrosion process of S-steel in acidic medium before and after polymeric coating. Furthermore were studied the effect of the preparing polymer on some strain of bacteria.

Sodium humate modified superabsorbent resin with higher salt‐tolerating and moisture‐resisting capacities

ABSTRACTThe superabsorbent resin (SAR) containing sodium humate (SH) has been synthesized by free‐radical graft copolymerization with acrylic acid, 2‐acrylamido‐2‐methylpropane sulfonic acid, and SH as monomers in aqueous solution, using N,N′‐methylenebisacrylamide as crosslinking reagent and potassium persulfate as initiator. The structure and morphology of the as‐prepared SARs were fully characterized by Fourier transform infrared , scanning electron microscopy and thermogravimetric analysis, respectively. Meanwhile, the effects of crosslinking reagent, initiator, SH, and neutralization degree on the water absorbency of SAR were studied. The results showed that the adding of SH in the SAR enhanced the salt‐tolerating and moisture‐resisting capacities obviously. The SAR without SH [poly(acrylic acid) (PAA)/2‐acrylamido‐2‐methyl‐1‐propanesulfonic (AMPS)] showed a maximum water absorbency of 600 g g−1 in distilled water and 60 g g−1 in 0.9 wt % NaCl solution, while SAR modified by SH (PAA/AMPS/SH) exhibited the maximum water absorbency of 1380 g g−1 in distilled water and 117 g g−1 in 0.9 wt % NaCl solution. Furthermore, the moisture‐resisting capacity of PAA/AMPS/SH decreases to 8 wt % compared with PAA/AMPS. PAA/AMPS/SH also has better water absorbency in different cation solutions. The results indicated that the introduction of SH could enhance the performance of SAR obviously. The possible reasons with this enhancement were also investigated. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46892.

Phenolphthalein-Conjugated Hydrogel Formation under Visible-Light Irradiation for Reducing Variability of Colorimetric Biodetection.

Polymerization-based signal amplification (PBA) is a colorimetric biodetection method for use in resource-limited settings. It uses phenolphthalein as a colorimetric reagent, but leaching of the dye from a resultant hydrogel can lead to variability in PBA results. In this work, we use polymerizable phenolphthalein in PBA to produce a phenolphthalein-conjugated hydrogel. Considering the photoinitiation mechanism of eosin Y and triethanolamine in air with an aqueous monomer solution, we determine reaction conditions for modified PBA that maintain a rapid polymerization response. Using the optimized conditions, we demonstrate that modified PBA can detect malaria antigen, PfHRP2, with reduced variability.

Effects of Chemical Composition on the Electromechanical Properties of Microfluidically Synthesized Hydrogel Beads

This investigation demonstrates microfluidic synthesis of monodisperse hydrogel beads with controllable electromechanical properties. Hydrogel beads were synthesized using aqueous monomer solutions containing difunctional macromer, ionic liquid monomer, and photoinitiator. Electromechanical properties of these beads were measured at compression ratios up to 20% to examine their potential use in vibrational energy harvesters. Bead stiffness decreased dramatically as water content increased from 19% to 60%. As water content and compression ratio increased, electrical permittivity of beads increased, while resistivity decreased. As ionic liquid monomer concentration increased from 0% to 4%, relative permittivity increased by 30–45% and resistivity decreased by 70–80%.

Two-dimensional tungstate nanosheets for constructing novel photochromic hydrogel with ultrahigh flexibility

A hydrogel possessing interesting photochromic behaviors was developed by in situ ultraviolet (UV) irradiation–assisted polymerization of an aqueous solution of N-isopropylacrylamide monomer in the presence of cesium tungstate nanosheets. By this process, a hierarchical porous network structure was finely constructed while showing ultrahigh flexibility. More importantly, the newly prepared hydrogel retained the photochromic properties of the cesium tungstate nanosheets. The color transitions could be readily controlled by UV laser irradiation and were completely reversible via laser exposure or dark treatment. The nanocomposite hydrogel with its excellent photochromic properties and ultrahigh flexibility will have great applications in flexible photochromic devices. The synthetic procedure is simple and has promises to be extended to developing other hydrogels with various new functionalities.

Electrochemically Generated Recognition Sites in Self‐doped Polyaniline Modified Electrodes for Voltammetric and Potentiometric Determination of Copper(II) Ion

AbstractChemical recognition elements for copper(II) ion have been generated in electrodes modified with poly(aniline‐co‐metanilic acid), P(An‐co‐MA), membrane and the resulting electrodes were used as selective sensors for voltammetric and potentiometric determination of this ion in an extended pH range. The P(An‐co‐MA) membrane was electrodeposited from aqueous mixed monomer solutions of An and MA, without the presence of a supporting electrolyte. For generating the recognition elements, P(An‐co‐MA) modified electrodes were subjected to several consecutive reduction/oxidation potential steps in copper(II) ion solution. It seems that during these potential steps, the receptor sites of the membrane are adjusted to the size, complexing property and hard/soft nature of copper(II) ion. This electrochemically mediated templating process, provided a selective sensor for determination of copper(II) ion. The results of preconcentration/differential pulse anodic stripping voltammetry, indicated analytical relation between the peak current and concentration of copper(II) from 1.0×10−9 to 1.0×10−4 M. The interference effect of various metal ions was explored and it was found that only mercury and silver ions show a considerable interference. The sensor exhibited selective potentiometric response for copper(II) over a wide concentration range (1.0×10−8 to 1.0×10−3 M) with a Nernstian slope of 27.9±0.3 mV per decade of copper(II) ion activity.

Synthesis of Anionic Hydrogels for Uranyl Ion Adsorption

In this study, the anionic hydrogels were prepared in existence of crosslinker (N, N’-methylenebisacrylamide) by free radical addition reaction in aqueous solutions of neutral acrylamide and 2-hydoxyethyl methacrylate monomers and anionic comonomers such as mesaconic acid with 2 carboxyl groups or aconitic acid with 3 carboxyl groups. Hydrogels were characterized by FT-IR and DSC analysis. The effects of temperature, pH, adsorbent mass and concentration on uranyl ion adsorption onto the anionic hydrogels were investigated. It was determined that adsorption of UO 2 2+ ions to prepared hydrogels did not change with temperature and increased with increasing pH. The adsorption of u ranyl ion from aqueous solutions onto the anionic hydrogels was evaluated by applying Giles, Langmuir and Temkin isotherms to experimental results. According to the Giles adsorption isotherms classification of hydrogels UO 2 2+ ions adsorption prepared from adsorption isotherms formed, L type was determined and Langmuir parameters were calculated. It was determined that adsorption of UO 2 2+ ions to hydrogels prepared from R L values calculated for 1000 mg L -1 UO 2 2+ ion concentration is favorable.

Removal of some cationic dyes from aqueous solution by acrylamide- or 2-hydroxyethyl methacrylate-based copolymeric hydrogels

In this study, anionic hydrogels were prepared using a crosslinker (N,N′-methylenebisacrylamide) through a free radical addition reaction in aqueous solutions of neutral acrylamide or 2-hydroxyethyl methacrylate monomer and anionic monomers, mesaconic acid or aconitic acid. Cationic dyes along with safranine (azine-), nile blue (oxazine-) and methylene blue (thiazine-) were selected as models of pollutants, and adsorption of these dyes onto the hydrogels was investigated. To examine the effect of concentration on adsorption, dye solutions prepared with a concentration range of 5–50 mg l−1 and 0.1 g hydrogel at 25 °C were exposed to the hydrogels until equilibrium was established. Dye adsorption onto the hydrogels was found to be an L type Giles adsorption isotherm. Monolayer sorption capacity and adsorption constant values were calculated from the Langmuir plots. To calculate RL values, a non-dimensional analysis was used and they were always found to be 0 azine > thiazine. Furthermore, the higher the number of carboxyl groups in the hydrogel composition, the higher the adsorbed amount of substance.

Supercritical continuous precipitation polymerization of acrylic acid in a droplet-based millifluidic device

In this work, a high pressure droplet-based millifluidic device was developed to achieve the continuous precipitation polymerization of acrylic acid in a green reaction medium: a supercritical mixture of 10 wt% ethanol in CO2 (15/19.5 MPa and 75 °C). To avoid clogging the tubular reactor of 762 µm ID, a segmented flow of an aqueous solution of monomer dispersed in the supercritical mixture (containing the initiator) was generated. During the reaction, the droplets were used as reservoirs which enable the continuous transfer of the monomer to the CO2-rich phase. This work shows that a large range of molar masses of poly(acrylic acid) (from 20,000 to 120,000 g.mol−1) with low polydispersity index (from 1.35 to 1.70) can be obtained. Due to the rapid transfer of the monomer compared to its conversion and the resulting low monomer concentration in the reactive medium, the molar mass distributions are not dependent on the residence time but rather on the initial monomer and initiator concentrations only. Hence in the investigated experimental conditions, the continuous reactive extraction process helps to achieve the precipitation polymerization without clogging the tubular reactor and in mastering the molar mass distribution. The effect of pressure influencing the molar mass distribution of poly(acrylic acid) as well as the competition between two possible loci of polymerization are also discussed.

Radical Copolymerization Kinetics of Bio-Renewable Butyrolactone Monomer in Aqueous Solution

The radical copolymerization kinetics of acrylamide (AM) and the water-soluble monomer sodium 4-hydroxy-4-methyl-2-methylene butanoate (SHMeMB), formed by saponification of the bio-sourced monomer γ-methyl-α-methylene-γ-butyrolactone (MeMBL), are investigated to explain the previously reported slow rates of reaction during synthesis of superabsorbent hydrogels. Limiting conversions were observed to decrease with increased temperature during SHMeMB homopolymerization, suggesting that polymerization rate is limited by depropagation. Comonomer composition drift also increased with temperature, with more AM incorporated into the copolymer due to SHMeMB depropagation. Using previous estimates for the SHMeMB propagation rate coefficient, the conversion profiles were used to estimate rate coefficients for depropagation and termination (kt). The estimate for kt,SHMeMB was found to be of the same order of magnitude as that recently reported for sodium methacrylate, with the averaged copolymerization termination rate coefficient dominated by the presence of SHMeMB in the system. In addition, it was found that depropagation still controlled the SHMeMB polymerization rate at elevated temperatures in the presence of added salt.

Aggregation Behavior and Electron‐Transfer Reaction of Dendritic Perylene Bisimide, Accompanied by the Formation of Highly Stable Anionic Radical Species

AbstractA polyethylene‐glycol‐functionalized perylene bisimide (PEPBI) was synthesized. Its concentration‐, solvent‐ and temperature‐dependent visible spectra were measured and its aggregation states were analyzed. PEPBI exists as an aggregate dimer in aqueous solution or predominantly as a monomer in organic solvents. The anionic surfactant sodium dodecylbenzenesulfonate (SDBS) can disperse PEPBI as a monomer in aqueous solution. The fluorescence of these solutions depends on the concentration of PEPBI and SDBS. The reduction of aggregated PEPBI with Na2S is slow and the monoanion radical as well as dianion species are the main forms of monomer. PEPBI exists predominantly as monomers in DMF and reacts with Na2S much faster. Interestingly, the anionic radical species exist in H‐aggregate form at low PEPBI concentrations and J‐aggregation occurs at high concentration. The dianion species is EPR‐silent and its color highly depends on its concentration in DMF.

Direct Electron Transfer to Cytochrome c Induced by a Conducting Polymer

The direct electron transfer (DET) to redox proteins has become a central topic in the development of biotechnological devices. The present work explores the mechanisms of the direct electrochemistry between cytochrome c (cyt c) and a conducting polymer, poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT–PSS). This polymer has been electrosynthesized from its monomers in aqueous solution on gold electrodes, and its capabilities for DET to cyt c have been examined by electrochemical and spectroelectrochemical methods. The polymer was electrodeposited with controlled thickness, and we determined that the electron transfer rate constant for cyt c oxidation was about 2 orders of magnitude higher than those obtained at conventional electrodes. Spectroelectrochemical measurements allowed us to evaluate the redox state of the polymer as a function of the potential and, in addition, the observation of intrinsic cyt c redox activity upon electron transfer from the conducting polymer. During ...