Radical Polymerization Of Acrylamide Research Articles

Fully Polymeric Conductive Hydrogels with Low Hysteresis and High Toughness as Multi‐Responsive and Self‐Powered Wearable Sensors

AbstractHigh mechanical strength, excellent toughness, low hysteresis, and robust resilience are of great importance for stretchable conductive hydrogels (CHs) to heighten their reliabilities for self‐powered sensing applications. However, it still remains challenging to simultaneously obtain the mutually exclusive performances. Herein, an intrinsically conductive and adhesive hydrogel is fabricated by one‐step radical polymerization of acrylamide (AAm), three hydroxy groups together clustered‐N‐[tris(hydroxymethyl)methyl]acrylamide (THMA), and cationic 1‐Butyl‐3‐Vinylimidazolium Bromide (ILs) dissolved in core‐shell structurally dispersed PEDOT:PSS (PP) solution. Owing to abundant clustered hydrogen bonds, electrostatic interactions between PILs chains and anionic PSS shells, and polymer chain entanglements, the CHs feature superior mechanical properties with a high tensile strength (0.25 MPa), fracture strain (1015%), fracture toughness (1.22 MJ m‐3), fracture energy of 36.5 kJ m‐2 and extremely low hysteresis (5%), and display excellent resilience and fatigue resistance. As a result, the CHs indicate excellent sensing properties with a gauge factor up to 10.46, a broad sensing range of strain (1‐900%) and pressure (0.05‐100 kPa), and fast responsive rate, thus qualifying for monitoring reliably and accurately large and tiny human movements in daily life. Moreover, the hydrogel‐assembled triboelectric nanogenerators (TENGs) exhibit excellent and stable electrical output performances, which are greatly promising in self‐powered flexible wearable electronics.

THERMAL PROPERTIES OF CROSS-LINKED POLYMERS BASED ON CHITOSAN AND POLYACRYLAMIDE

The thermal properties of cross-linked polymers based on chitosan and polyacrylamide were studied. Samples of the resulting network polymers, which included chains of polyacrylamide and chitosan, were obtained as hydrogel materials by radical polymerization of acrylamide in the presence of chitosan using the redox system of cerium (IV) ammonium nitrate as an initiator and N,N’-methylene-bis-acrylamide as a crosslinker. The structure of the obtained polymers was confirmed by comparing their IR spectra with the spectra of chitosan and polyacrylamide. It was shown that in the IR spectrum of the chitosan-containing sample, the peak at 2932 cm -1 indicates the presence of CH2 groups in the polymer chains and the formation of cross-links. Deformation and valence vibrations of the amide group in polyacrylamide are observed at 1600–1660 cm -1, and the band at 1633 and 1411 cm -1, which appears when the amide bond of polyacrylamide is formed, corresponds to C-N vibrations in the graft copolymer. These characteristic bands confirm the possibility of graft copolymerization of acrylamide on chitosan. The influence of the mass ratio of chitosan and polyacrylamide on the thermal properties of polymer systems was investigated by the method of thermogravimetric and differential thermogravimetric analysis. Atmospheric gas (1 bar, 40 % relative humidity) was used in all thermoanalytical measurements. The samples were examined after vacuum drying at 4 × 10-7 bar and 60 °C using Concentrator Plus. TGA and DTG curves were obtained in the temperature range from 30 to 500 °C with a scanning speed of 5 °C/min using 40 μl aluminum oxide crucibles. It was established that increasing the concentration of chitosan during synthesis reduces the amount of bound water in the obtained samples. Analysis of thermal destruction at the final stages of heating indicates that the presence of chitosan in samples of cross-linked polymers increases their heat resistance by 10–15 °C. The obtained regularities can be used in the creation of composite materials for hydrogel wound dressings and covering medical agents for external use.

Kinetics of the Water Release of Hygroscopic Acrylamide Gel Embedded in Calcium Chloride by Thermogravimetric Analysis

Poly (acrylamide) gel was synthesized by radical polymerization of acrylamide and N, N'-methylene-bisacrylamide in the presence of benzoyl peroxide and carbon nanotubes. The dry product was saturated with calcium chloride and prepared for water absorption and desorption. The kinetics of water desorption of poly (acrylamide) gel embedded with hygroscopic calcium chloride (DHG), was studied from thermograms data of thermogravimetric analysis (TGA). DHG captures vapor from the environment and releases it as fresh water; it can be used as the condenser to build atmospheric water generators (AWGs) to alleviate the freshwater stress rusting from innovative activities such as industrial, agricultural, rural, and defense endeavors. The kinetics parameters of the synthesized DHG showed that it absorbed environmental vapor at room temperature and released water below its boiling point (40 to 90 °C), temperatures achievable under sunlight via the photothermal effect.

One-step coaxial spinning of core-sheath hydrogel fibers for stretchable ionic strain sensors

High-strength, highly conductive, and stretchable conductive fibers are essential for the development of flexible electronic devices. Here, we develop a continuous coaxial wet-spinning method to fabricate stretchable, conductive, and freeze-resistant hydrogel fibers with a core-sheath structure. The core is a supramolecular hydrogel, poly (APhe-co-AAm) (PAPAM), obtained by radical polymerization of acrylamide (AAm) and acryloyl-l-phenylalanine (APhe), and the sheath consists of PVDF-HFP and PU with hydrochloric acid as the coagulation bath. The hydrogel fibers exhibit excellent mechanical properties with a tensile strength of 3.1 MPa and elongation at a break of 750 %. Hydrochloric acid plays two roles in this system: one is to promote hydrophobic association and hydrogen bond formation and improves mechanical properties, and the other is to provide plentiful ions to confer excellent electrical conductivity (10.59 S m−1) and freezing resistance (-20 °C). The application of fiber strain sensors for detecting human motion and pressure sensing demonstrates great potential as wearable electronic devices.

Antimicrobial MXene-based conductive alginate hydrogels as flexible electronics

Flexible electronics have received considerable attention for their potential applications in wearable human health monitoring. Recently, conductive hydrogels have shown great potential in the application of flexible electronic devices. However, the restricted space of the 2D plane restricts the performance of MXene sensors, and conventional conductive hydrogels lack antibacterial properties, limiting their deep application in biomedical-related products. To overcome these limitations, we proposed an antibacterial and conductive MXene-SA-TSA-AM hydrogel through the radical polymerization of acrylamide in this work. Specifically, the coupling between sodium alginate (SA) and dimethyloctadecyl-(3-trimethoxysilylpropyl) ammonium chloride (TSA) brought about excellent antibacterial properties. MXene-SA-TSA-AM Hydrogels showed compelling swelling ratios (36–38 times), great mechanical properties (up to 1780 %), excellent self-healing ability (<10 min), and reproducible adhesion. During the pressure sensor applications, MXene-SA-TSA-AM hydrogels were demonstrated to accurately and rapidly monitor human physiological activities of finger bend and pulse with a rapid response (<0.2 s) and high stability (up to 5000 cycles). Furthermore, the MXene-SA-TSA-AM hydrogel exhibited excellent antibacterial properties, which can successfully inhibit Staphylococcus aureus and Escherichia coli with efficiency up to 99.6 % and 99.3 %, respectively. Finally, we anticipated that this novel antibacterial and conductive MXene-SA-TSA-AM hydrogel would further promote the deeper application of flexible electronics in biomedical-related products.

Simultaneous Cryogenic Radical and Oxidative Coupling Polymerizations to Polyaniline/Polyacrylamide Conductive Cryogels for Gas Sensing.

The macro-porous structure of polymer cryogels provides an appropriate channel for the adsorption and transport of substances, endowing its application in the field of electrochemical sensing. The combination mode of a polymer matrix and electro-active substance, particularly the distribution of an electro-active substance in the matrix, has an important effect on the overall performance of the sensor. In this work, through the simultaneous oxidation coupling polymerization of aniline (ANI) and radical polymerization of acrylamide (AAm) under cryogenic condition, conductive composite cryogels were prepared, aiming for the uniform distribution of PANI in the PAAm matrix. The possibility of simultaneous polymerizations was symmetrically investigated, and the obtained PANI/PAAm cryogels were characterized. Due to the acid-doping of PANI, the electrical conductivity of PANI/PAAm cryogels could be modulated with acidic and basic gases. Thus, the performance of the gas sensor was studied by making conductive PANI/PAAm cryogel sheets as resistive sensor electrodes. We found that the content of PANI, the sheet thickness and the dry/wet state of the cryogel influenced the response sensitivity and rate as well as the recovery properties. The response duration for HCl and NH3 gas was shorter than 70 and 120 s, respectively. The cyclic detection of HCl gas and the alternate detection of NH3/HCl were achieved. This gas sensor with advantages, including simple preparation, low cost and high sensitivity, would have great potential for the application to monitor the leakage of acidic and basic gases.

In situ growth of the ZIF‐8 on the polymer monolith via CO2‐in‐water HIPEs stabilized using metal oxide nanoparticles and its photocatalytic activity

AbstractHere, the ZnO/polyacrylamide (ZnO/PAM) macroporous composite monolith was first prepared through the radical polymerization of acrylamide in ZnO‐costabilized CO2‐in‐water Pickering high internal phase emulsions (HIPEs). An efficient and green synthesis method was used to prepare the ZnO/PAM porous precursor materials, and ZnO nanoparticles (NPs) were used as a metal ion source to grow the metal organic frameworks (MOF) phase through secondary recrystallization, thereby synthesizing the target MOF/PAM porous monolith. The effects of the contents of ZnO NPs on the formation of HIPEs and properties of the target MOF/PAM composites for the photocatalytic degradation of cationic dye were studied. As the content of ZnO NPs increased to 3.75 wt%, the composite monolith had high mechanical stress (0.24 MPa) at 80% strain and recovered their shape. The as‐synthesized ZIF‐8/PAM composites were characterized using X‐ray diffraction, scanning electron microscope (SEM), Brunauer Emmett Teller (BET), energy dispersive X‐ray spectrometer (EDS) mapping, and TG methods. SEM images showed that the hybrid materials were interconnected, and the sizes of the open macropore and interconnected pore throats were 30–125 and about 2–20 μm, respectively. In addition, the ZIF‐8/PAM material could be used as a high‐efficiency photocatalyst to remove the cationic dye at a fast rate (88.6%).

Correction: Tacticity, molecular weight, and temporal control by lanthanide triflate-catalyzed stereoselective radical polymerization of acrylamides with an organotellurium chain transfer agent

Correction for ‘Tacticity, molecular weight, and temporal control by lanthanide triflate-catalyzed stereoselective radical polymerization of acrylamides with an organotellurium chain transfer agent’ by Yuji Imamura et al., Polym. Chem., 2020, DOI: 10.1039/d0py01280g.

One-Shot Preparation of Polyacrylamide/Poly(sodium styrenesulfonate) Double-Network Hydrogels for Rapid Optical Tissue Clearing.

In this study, we propose a convenient method for the synthesis of double-network gels by the one-shot radical polymerization for their application to rapid optical tissue clearing. Double-network gels were produced during the radical polymerization of acrylamide (AAm) and sodium styrenesulfonate (SS) in the presence of N,N′-methylenebisacrylamide and sodium divinylbenzenesulfonate as the cross-linkers by simultaneous addition, that is, one-shot polymerization accompanying the delay of polymerization for a second network monomer. We analyzed the polymerization process based on the consumption rates of each monomer during the reactions in the absence of the cross-linkers in order to estimate the repeating unit structure of the resulting polymers. We then fabricated the AAm/SS gels by the polymerization of AAm and SS in the presence of the cross-linkers. We analyzed the swelling, viscoelastic, and mechanical properties of the produced gels to investigate their network structure. Finally, we demonstrated the validity of the double-network gels for the application to rapid optical tissue clearing.

Magnetostriction in ferrogels based on physical and chemical networking with embedded strontium hexaferrite particles

Magnetostriction of ferrogels based on physical and chemical networking with embedded strontium hexaferrite particles was studied in 420 mT uniform magnetic field. Ferrogel with physical networking was based on natural polysaccharide – guar gum, which gelates due to formation of H-bonds. Ferrogel with chemical networking was synthesized by radical polymerization of acrylamide. Magnetostriction of the physical ferrogel resulted in the increase of length of the gel specimen along the field lines and in the proportional decrease of its width in the direction across the field lines. In case of chemical ferrogel, both the length and the width increased in the uniform magnetic field leading to the increase of the ferrogel volume.

Synthesis, characterization and rheological properties of acrylamide/ acidic monomer/ N-(4-ethylphenyl) acrylamide Terpolymers as pH- responsive hydrogels and nanogels

ABSTRACTNovel pH-responsive superabsorbent hydrogels (HGs) and nanogels (NGs) with high water uptake and adjustable viscoelastic behavior were synthesized by free radical polymerization of acrylamide (AM) and a small amount of N-(4-ethylphenyl)acrylamide (EΦAM) hydrophobic comonomer in the presence of three different acidic monomers. Structure of the synthesized linear terpolymers was investigated by 1H-NMR spectroscopy. The solution viscosity of the linear terpolymers was measured at different pH and temperatures, where AM-EΦAM-AMPS terpolymer showed higher viscosity in different conditions. Equilibrium swelling ratio (ESR) of hydrogels was studied using response surface methodology and empirically modeled as a function of pH and temperature as stimuli.

Ferrogels Ultrasonography for Biomedical Applications.

Ferrogels (FG) are magnetic composites that are widely used in the area of biomedical engineering and biosensing. In this work, ferrogels with different concentrations of magnetic nanoparticles (MNPs) were synthesized by the radical polymerization of acrylamide in stabilized aqueous ferrofluid. FG samples were prepared in various shapes that are suitable for different characterization techniques. Thin cylindrical samples were used to simulate the case of targeted drug delivery test through blood vessels. Samples of larger size that were in the shape of cylindrical plates were used for the evaluation of the FG applicability as substitutes for damaged structures, such as bone or cartilage tissues. Regardless of the shape of the samples and the conditions of their location, the boundaries of FG were confidently visualized over the entire range of concentrations of MNPs while using medical ultrasound. The amplitude of the reflected echo signal was higher for the higher concentration of MNPs in the gel. This result was not related to the influence of the MNPs on the intensity of the reflected echo signal directly, since the wavelength of the ultrasonic effect used is much larger than the particle size. Qualitative theoretical model for the understanding of the experimental results was proposed while taking into account the concept that at the acoustic oscillations of the hydrogel, the macromolecular net, and water in the gel porous structure experience the viscous Stocks-like interaction.

Enhancement of thermal stability of drilling fluid using laponite nanoparticles under extreme temperature conditions

Aiming to overcome the problem of polymer degradation in water based drilling fluids under high temperature, this letter examined the influence of laponite nanoparticles on the thermal stability of drilling fluids. Firstly, a terpolymer (AAD) was synthesized through radical polymerization of acrylamide, 2-acrylamido-2-methylpropane sulfonic acid, and diallyldimethylammonium chloride monomers. The presence of laponite nanoparticles significantly improved the onset decomposition temperature and viscosities of AAD terpolymer at high temperatures, according to thermogravimetric analysis (TGA) and high temperature high pressure (HTHP) rheology results, respectively. Thereafter, water based drilling fluids containing AAD and laponite were formulated and aged under different temperatures. The drilling fluids containing laponite had a substantially higher viscosity than that without laponite ascribing to strong interactions between laponite and functional groups of the ADD terpolymer. This letter provided us a novel strategy to develop high temperature resistant drilling fluids for deep reservoir excavation.

Synthesis of interpenetrating polymer networks using silicone polymer with silanol residue

Silicone polymers containing the silanol residue were prepared from a silica gel and were successively used for the synthesis of interpenetrating polymer networks (IPNs) with acrylamides, such as N-isopropylacrylamide (NIPAM) and N,N-dimethylacrylamide. During gelation, the condensation of silanols to form a siloxane linkage and the radical polymerization of acrylamides with a cross-linker simultaneously proceeded to afford IPNs composed of both the silicone polymer and polyacrylamide gels. The swelling properties of the obtained IPNs were then investigated. For example, the IPNs synthesized with NIPAM showed a much lower percentage of equilibrium mass swelling (PES) values at 3 °C in water, 378–545%, than the NIPAM polymer gel (>1500%), and in addition, these IPNs barely showed an apparent volume phase transition temperature (VPTT) in contrast to the NIPAM polymer gel.

Synthesis, evaluation and aqueous solution behavior of the cationic fluorinated hydrophobically associating polyacrylamide

Hydroxypropyl acrylate-N-diethyl-perfluorooctane sulfonamide (HAF), a novel surface active cationic fluorinated monomer, is designed and synthesized in this study. The structure of HAF and its intermediate product are characterized by FT-IR and 1H-NMR. Then the hydrophobically associating polyacrylamide (PMHAF) is prepared by free radical polymerization of acrylamide, 2-Acrylamido-2- methylpropane sulfonic acid and HAF in an aqueous solution. The structure and composition of PMHAF are characterized by FT-IR, 1H-NMR, XPS and Tg. Macroscopic and microscopic self-assembly associative properties in solutions of PMHAF are studied via viscosimetry, SEM and AFM. The result show that with the polymer concentration increase, the viscosity increased and the critical association concentration (CAC) is about 1.09 g.L−1. Moreover, the active of PMHAF solution are examined with surface tension, interfacial tension (IFT) and contact angle. The CAC values of PMHAF in water and in salt from surface tension are 1.39 g.L−1 and 1.22 g.L−1 respectively. Copolymers can reduce the interfacial tension between crude oil from Xinjiang Oilfield /water, and the final values of IFT is around 0.0243 mN.m−1 and PMHAF solution has good potential on change of wettability. All of these properties indicate that the fluorinated hydrophobically associating polyacrylamide is an excellent chemical for chemical enhanced oil recovery.

EFFECT OF THE POLYACRYLAMIDE FERROGEL ELASTICITY ON THE CELL ADHESIVENESS TO MAGNETIC COMPOSITE

Biocompatible polyacrylamide gels are widely required for the development of mechanically “soft” magnetic material for the purposes of different biomedical applications. In this work, ferrogels were synthesized by radical polymerization of acrylamide in a stable aqueous suspension of magnetic maghemite [Formula: see text]-Fe[Formula: see text]O[Formula: see text] nanoparticles (MNPs) with the median value in diameter of 11.4[Formula: see text]nm fabricated by laser target evaporation. Gel network density was set to 1:100, the concentrations of embedded MNPs were fixed at 0.00%, 0.25%, 0.50%, 0.75% or 1.0% by weight. Ferrogels’ Young’s modulus and affinity to the human dermal fibroblasts adhesiveness were tested. To estimate the cells adhesive activity to gels, the adhesion index was calculated as the number of adhered cells divided by the number of cells sown and multiplied by 100%. The gradual increase of MNPs concentration in the gel network resulted in the significant increase of ferrogel’s Young’s modulus and cells adhesion activity. In particular, at the MNPs concentration of 0.25%, the modulus and the adhesion index were equal to [Formula: see text]30[Formula: see text]kPa and [Formula: see text]90%, correspondingly. The adhesion index at highest MNPs concentration of 1.0% was close to 100% and modulus to [Formula: see text]40[Formula: see text]kPa. The increase of cells adhesiveness rise with MNPs concentration closely correlated with the direct impact of MNPs on the gel stiffness.

Synthesis and characterization of acrylamide/(3-acrylamidopropyl) trimethyl ammonium chloride solution and acrylamide/Na-montmorillonite hydrogels via controlled radical polymerization for use as high-temperature and high-salinity oil reservoirs

Water-soluble copolymers of acrylamide (AM) and (3-Acrylamidopropyl) trimethyl ammonium chloride (APTAC) and Na-montmorillonite (Na-MMT) were prepared by controlled radical polymerization of AM, APTAC, and Na-MMT clay using potassium persulfate (KPS) and sodium metabisulfite (MBA) as redox initiator and cobalt acetyl acetone (Co(acac)2) as a catalyst in an aqueous solution. The synthesized PAAM copolymers were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). XRD and FTIR indicated the formation of APTAC/PAAM/Co(acac)2 and PAAM/Na-MMT Co(acac)2 copolymers and also showed that the interplanar spacing increased due to intercalation formation between the clay layers. DSC indicated an increase in the thermal stability of the mentioned hydrogels, and some increases the glass transition temperature of the PAAM hydrogel in the presence of the nanoclay. The Co(acac)2 controlled the chain polymerization via a reversible activation–deactivation of the chains, so the storage modulus of the hydrogel increases significantly. Hydrogels with acceptable gel strength, gelation time, and gel stability were prepared by cross-linking of the aqueous solutions of the synthesized nanocomposite copolymer with Chromium (III) acetate for use in water shutoff operations in oil reservoirs. The effects of pH, salinity, Co(acac)2, temperature, and the presence of clay minerals on the gelation time were investigated, and the activation energies were measured. With increasing temperature, gelation occurred more rapidly. Addition of Co(acac)2 increased the loss and storage modulus, because of reversible activation–deactivation radical polymerization and decreased the gel swelling. The polymer chains diffused between the clay layers so the elastic modulus (G′) of the prepared hydrogels increased, and a reversible interaction between clay and acrylamide chains led to increase in loss modulus (G′′).

Biomimetic gels with chemical and physical interpenetrating networks

AbstractThis study aimed to create and to characterize the functional properties of gels with semi‐interpenetrating network (semi‐IPN) with focus on possible use of these composites in biomedical engineering. Polyacrylamide as a synthetic biocompatible polymer was chosen for the chemical network. The physical network comprised the gel‐forming polysaccharides xanthan gum or gellan gum. Gels were synthesized by radical polymerization of acrylamide in aqueous solutions of polysaccharides. Mechanical and electrical properties of gels with 0.2, 0.4, 0.6, 0.8 and 1.0 wt% content of polysaccharide were investigated. It was found that the inclusion of a small amount of xanthan or gellan into the polymeric network of a polyacrylamide gel significantly shifts the gel electrical potential towards the rest potential of living cells and Young's modulus towards the elasticity limits of biological soft tissues like non‐activated muscles. From the viewpoint of biomedical applications, the main advantage of the proposed composites is that the semi‐IPN structure provides a nonlinear dependence of gel tension on gel deformation, which mimics the elasticity of natural tissues. This feature opens the possibility for the promising use of the proposed gels for musculoskeletal minibioimplants or scaffolds for tissue engineering. © 2018 Society of Chemical Industry

Plastic antibodies tailored on quantum dots for an optical detection of myoglobin down to the femtomolar range

A highly sensitive fluorescence detection probe was developed by tailoring plastic antibodies on the external surface of aqueous soluble quantum dots (QDs). The target was Myoglobin (Myo), a cardiac biomarker that quenched the intrinsic fluorescent emission of cadmium telluride (CdTe) QDs capped with mercaptopropionic acid (CdTe-MPA-QDs). The QDs were incubated with the target protein and further modified with a molecularly-imprinted polymer (MIP) produced by radical polymerization of acrylamide and bisacrylamide. The main physical features of the materials were assessed by electron microscopy, dynamic light scattering (DLS), UV/Vis spectrophotometry and spectrofluorimetry. The plastic antibodies enabled Myo rebinding into the QDs with subsequent fluorescence quenching. This QD-probe could detect Myo concentrations from 0.304 to 571 pg/ml (50.6 fM to 95 pM), with a limit of detection of 0.045 pg/ml (7.6 fM). The proposed method was applied to the determination of Myo concentrations in synthetic human serum. The results obtained demonstrated the ability of the modified-QDs to determine Myo below the cut-off values of myocardial infarction. Overall, the nanostructured MIP-QDs reported herein displayed quick responses, good stability and sensitivity, and high selectivity for Myo, offering the potential to be explored as new emerging sensors for protein detection in human samples.

Magnetoimpedance biosensor prototype for ferrogel detection

Ferrogels are composite materials widely introduced in the area of biomedical engineering as magnetic field sensitive transformers. These biomimetic materials can be prepared by incorporating monodomain magnetic nanoparticles into chemically crosslinked hydrogels. The properties of a biomimetic ferrogels taken for the study unlike that of the biological prototype might be set up by the synthesis and can be thoroughly controlled in a physical experiment. In this work we developed a giant magnetoimpedance sensor with a multilayered FeNi/Ti-based sensitive element adapted for ferrogel studies. Ferrogels were synthesized by radical polymerization of acrylamide in a stable aqueous suspension of γ-Fe2O3 MNPs fabricated by laser target evaporation. The magnetoimpedance measurements in initial state and in the presence of ferrogels with concentrations of nanoparticles from 0 to 2.4wt% in a frequency range of 1–300MHz allowed a precise characterization of the stray fields of the nanoparticles present in the ferrogel.