Pure Poly Acrylic Acid Research Articles

Synthesis of a novel clay/polyacrylic acid-tannic acid hydrogel composite for efficient removal of crystal violet dye with low swelling and high adsorption performance

Hydrogels are versatile materials with numerous applications; however, their potential in water treatment is hindered by their tendency to exhibit high swelling, degradation, and excessive water absorption. In this study, a hydrogel composed of natural clay, polyacrylic acid (PAA), and tannic acid (TA) was prepared with varying ratios of TA to control swelling ratio, reduce degradation and enhance adsorption efficiency for removal of cationic dye-contaminated wastewater. The effect of the TA ratio on the physical, chemical, and adsorption properties of prepared hydrogel (clay/PAA-TA) was studied by preparing a series of hydrogel composites and characterizing them using various techniques. The swelling ratio of pure PAA hydrogels was 7061%, but by incorporating TA into the polymer mixture, the swelling ratio decreased to less than 500%, with the lowest observed swelling of 250% occurring at a 5% tannic acid. In adsorption studies, the target pollutant was crystal violet dye (CV) and the pH effect, time effect, temperature and initial dye concentration for the adsorption CV dye were investigated using batch adsorption parameters. Adsorption studies showed that using 5% of TA is the optimal ratio to achieve the highest adsorption capacity of the prepared clay/PAA-TA to uptake CV dye. With an adsorption capacity of 444.5 mg/g, the Langmuir-Freundlich model suited the adsorption isotherm. The adsorption kinetics were best explained by the pseudo-first-order model. The results of thermodynamic studies indicated that the adsorption was spontaneous, favorable, and endothermic.

Boron nitride microfiber reinforced polyacrylic acid hydrogels with excellent self-adhesion, fast pH response, and strain sensitivity.

Hydrogels are widely utilized in the sensor field, but their inadequate adhesion presents a significant obstacle. Herein, a new multifunctional BNMFs/PAA composite hydrogel was prepared via the incorporation of one-dimensional porous boron nitride microfibers (BNMFs) and polyacrylic acid (PAA) hydrogels. BNMFs, as a reinforcing filler, play a very important role in enhancing the properties of the composite hydrogels. In particular, the porous micrometer structure plays a unique role in improving the adhesion properties of PAA hydrogels. The steric hindrance and the rich hydroxyl functional groups coming from BNMFs are key factors for the excellent adhesion of the composite hydrogels. The composite hydrogels show strong adhesion to various substrate materials. For iron plates and biological tissues, the adhesion energy can reach 1377 J m-2 and 317 J m-2, respectively. In addition, the developed BNMFs/PAA composite hydrogels exhibit excellent mechanical properties. The fracture strain of the composite hydrogels is increased by 2.4 times compared to pure PAA hydrogels. The hydrogen bonds formed between BNMFs and PAA are conducive to the mechanical properties of the BNMFs/PAA composite hydrogels. Meanwhile, BNMFs as fillers play a role in carrying and dissipating force. Furthermore, the BNMFs/PAA composite hydrogels have excellent strain and pH response characteristics. This is because the crosslinking network of the composite hydrogels becomes loose after the addition of BNMFs, resulting in rapid ion transport pathways. Therefore, the developed BNMFs/PAA composite hydrogels will have broad application prospects in the fields of motion monitoring, intelligent skin and biological adhesives.

Multi-chambered flame retardant microcapsules containing bisphenol A-bis (diphenyl phosphate) and zinc borate prepared by Pickering emulsions polymerization and their application in water-borne polyacrylic acid coatings

Multi-chambered flame retardant microcapsules (ZB-FRM) containing bisphenol A-bis(diphenyl phosphate) (BDP) and zinc borate (ZB) with calcium alginate (CA) shells were prepared by Pickering emulsions polymerization. The aim was to microencapsulate BDP to form a CA shell with many hydroxyl groups, improve its compatibility with aqueous polyacrylic acid (PAA), and reduce the flammability of PAA by using the flame suppression ability of BDP. Next, the high smoke generation caused by BDP was suppressed and the mechanical properties of the flame retardant coating were improved by introducing ZB in the shell layer. The thermal properties of the microcapsules, the mechanical and flame retardant properties in aqueous substrates, and smoke generation during cone calorimetry tests were tested. It was found that ZB-FRM had good compatibility with PAA. The introduction of ZB-FRM increased PAA's limiting oxygen index (LOI) to 25.5% and vertical combustion level to V-0. ZB improved the thermal stability of the microcapsules, the mechanical properties of the flame retardant coating, and the reduced smoke from BDP by 19.9%. However, ZB inhibited the initial flame retardant mechanism of BDP, resulting in a slight decrease in LOI, but still, a 6.9% improvement compared to pure PAA.

Microencapsulation of bisphenol A‐bis(diphenyl phosphate) by Pickering emulsions polymerization and its application in water‐borne polyacrylic acid coatings

AbstractFor improving the compatibility of oil‐based flame retardants and waterborne substrates, Bisphenol A‐bis(diphenyl phosphate) (BDP) is used as the dispersed phase, sodium alginate (SA) solution as the continuous phase, and hydrophilic silica as the emulsifier in the preparation of stable oil‐in‐water (O/W) Pickering emulsions. Then, the emulsions are added into CaCl2 solution in the atomized form to polymerize the aqueous phase to calcium alginate (CA) and to obtain BDP/SiO2/CA microcapsules. BDP/SiO2/CA microcapsules are used as a flame retardant to improve the fire safety of waterborne polyacrylic acid (PAA) coatings. To verify that BDP/SiO2/CA is successfully prepared, Fourier‐transform infrared spectra (FTIR) and scanning electron microscopy (SEM) are used after microencapsulation. The results show that the physical barrier formed by the SiO2 particle layer has successfully stabilized the BDP in the CA gel network. Subsequently, the flame retardance of PAA with BDP/SiO2/CA is tested using limiting oxygen index (LOI) test and cone calorimeter(CONE) test. Compared with pure PAA, when BDP/SiO2/CA (4:6) microcapsules are added at 20 wt %, the LOI of the PAA coating is increased from 18.6% to 28.4%, the peak heat release rate (PHRR) value of that is reduced by 52.66%. The microcapsules endow oily BDP hydrophilicity and good compatibility with waterborne PAA coatings.

A multifunctional hydrogel fabricated via ultra-fast polymerization by graphene oxide-adsorbed liquid metal nanodroplets

Graphene structures have never been found to play a role in accelerating fabrication of functional hydrogels. In this work, it is initially discovered that multifunctional hydrogels are fabricated via ultra-fast polymerization (∼minutes) by graphene oxide-adsorbed liquid metal nanodroplets (LMNPs@GO) vs. by conventional approaches (∼hours/days). LMNPs@GO are used to rapidly initiate and further cross-link polyacrylic acid (PAA) chains into a three-dimensional (3D) network without any extra molecular initiators, cross-linkers, heat source, and/or protective gas. The polymerization process with LMNPs@GO is extremely faster than that without GO involved (20 s vs. 4 h of prepolymer formation, and then 10 min vs. 3 days of crosslinking) for free radical polymerization of PAA hydrogels. The resulting hydrogel with 2 wt% reduced graphene oxide (rGO) exhibits 600% increase in tensile strength and 950% enhancement in conductivity, as well as excellent self-healing capabilities, in comparison with that of the pure PAA. The sensitivity studies show its great potential for the application of flexible sensors. Furthermore, the hydrogel possesses good dissolving properties, which is greatly beneficial for recyclability of the LM. This creative study not only broadens a novel application of graphene for making advanced multifunctional polymer materials, but also provides a brand-new route to realization of ultra-fast manufacturing technology that is significantly promising for industrial production in wearable devices.

Fluorinate polyacrylic acid and its use as a potential adjuvant field

This study describes a polymer potentially used as a vaccine adjuvant. We first synthesized a novel polyacrylic acid modified by perfluorinated butanol—a bioactive compound that is biocompatible. The main aim was to functionalize the polyacrylic acid by fluorine. This functionalization could offer a permanent graft by an esterification reaction. The chemical structure of the polymer has been characterized by the hydrogen nuclear magnetic resonance spectrum (1H-NMR) and fourier transform infrared spectrum (FT-IR). Thermal analysis showed that the esterification reaction was successful on the polyacrylic acid. Viscosity testing showed that the viscosity of the sample aqueous solution increases along with esterification. The surface tension of the polymer was also tested. The results show that the surface tension of the polyacrylic acid markedly decreased when modified by fluorine. Finally, the interaction of these materials with macrophages was tested on cell test. Results showed that the modified polyacrylic acid performed better improve the activation effect than pure polyacrylic acid in 1L-1β.

Vacuum resistance treated ZIF-8 mixed matrix membrane for effective CH4/N2 separation

• Highly vacuum resistance treated ZIF-8@VR by surface-carbonization was used as filler of MMM. • ZIF-8@VR shows good membrane-forming property and high acidic stability. • PAA/ZIF-8@VR MMM showed unprecendent CH 4 permeance and good CH 4 /N 2 selectivity. CH 4 /N 2 separation, a viable way to purify energy gas and reduce the greenhouse effect, requires the use of highly gas permeable membrane, but acid environment affects the membrane stability. In this work, the ZIF-8@VR nanoparticle was synthesized via a high vacuum resistance sintering method (VRSM), which increased the acid resistance to pH 2.8 because of surface carbonization and stiffening. The structure of the ZIF-8@VR nanoparticle was investigated by XRD, SEM, FTIR, BET and Raman analysis, followed by blending it with polyacrylic acid (PAA) to fabricate PAA/ZIF-8@VR mixed matrix membranes (MMMs). The MMMs exhibited excellent CH 4 permeance and satisfactory CH 4 /N 2 selectivity, with the optimal CH 4 permeance (~1763 GPU) for the MMM with 66.8 wt% ZIF-8@VR filler. Furthermore, compared with pure PAA membrane, the MMMs with ZIF-8@VR filler could improve the CH 4 /N 2 selectivity from 1.3 to 3.1.

Mechanical Properties of a Supramolecular Nanocomposite Hydrogel Containing Hydroxyl Groups Enriched Hyper-Branched Polymers.

Owing to highly tunable topology and functional groups, hyper-branched polymers are a potential candidate for toughening agents, for achieving supramolecular interactions with hydrogel networks. However, their toughening effects and mechanisms are not well understood. Here, by means of tensile and pure shear testings, we characterise the mechanics of a nanoparticle–hydrogel hybrid system that incorporates a hyper-branched polymer (HBP) with abundant hydroxyl end groups into the matrix of the polyacrylic acid (PAA) hydrogel. We found that the third and fourth generations of HBP are more effective than the second one in terms of strengthening and toughening effects. At a HBP content of 14 wt%, compared to that of the pure PAA hydrogel, strengths of the hybrid hydrogels with the third and fourth HBPs are 2.3 and 2.5 times; toughnesses are increased by 525% and 820%. However, for the second generation, strength is little improved, and toughness is increased by 225%. It was found that the stiffness of the hybrid hydrogel is almost unchanged relative to that of the PAA hydrogel, evidencing the weak characteristic of hydrogen bonds in this system. In addition, an outstanding self-healing feature was observed, confirming the fast reforming nature of broken hydrogen bonds. For the hybrid hydrogel, the critical size of failure zone around the crack tip, where serious viscous dissipation occurs, is related to a fractocohesive length, being about 0.62 mm, one order of magnitude less than that of other tough double-network hydrogels. This study can promote the application of hyper-branched polymers in the rapid evolving field of hydrogels for improved performance.

Preparation and characterization of hydrogel nanocomposite based on nanocellulose and acrylic acid in the presence of urea

In this study, acrylic acid (AA) and cellulose nanofibers (CNFs) were used as main materials to synthesize an acrylic-nanocellulose hybrid hydrogel nanocomposite in the presence of urea. The interpenetrating polymer networks were obtained by radical polymerization in different urea: AA ratios (0:10, 1:10, 3:10, 5:10, 10:10). Fourier transform infrared spectroscopy (FTIR) combined with X-ray diffraction (XRD) and elemental analysis techniques confirmed the chemical interaction of urea in the network structure. Free absorption and water absorption under load (AUL) of the synthesized hydrogels varying in urea: acrylic acid weight ratios were measured in distilled water and saline (0.9 wt%) solution for hybrid (5 wt% CNFs) and pure polyacrylic acid (0 wt% CNFs) hydrogels. It was found that incorporation of urea and CNFs in the hybrid structure generating compact hydrogel networks with high crosslink density leading to lower absorption with and without pressure, whereas incorporation of urea in the structure resulted in a more extended network with higher absorption capacity (about 3×) than hybrid structure.

Enhanced mechanical property of polyacrylic acid composite hydrogel by the synergistic role of core-shell structured SiO2@PDMAEMA nano-objects

In this work, several polyacrylic acid (PAA) nanocomposite hydrogels containing different dimensional silica nanoparticles densely grafted with poly(2-(dimethylamino)ethyl methacrylate) (SiO2@PDMAEMA nano-objects) have been fabricated. Firstly, the spherical and sheetlike SiO2@PDMAEMA core/shell nano-objects were prepared based on self-assembly of poly(2-(dimethylamino)ethyl methacrylate)-block-poly(3-(triethoxysilyl)propyl methacrylate) (PDMAEMA-b-PTEPM) gelable block copolymers in bulk. Then, two different shaped SiO2@PDMAEMA nano-objects were introduced into the PAA hydrogel construction processes to obtain the corresponding PAA composite hydrogel, respectively. The results indicated that core/shell nano-objects were well dispersed in the PAA matrix, and the ionic bonds were formed between –N(CH3)2 groups in shell of nano-objects and –COOH units in matrix. The compressive strength of composite hydrogels containing 1–3 wt% of sheetlike or spherical nano-objects dramatically increased. For example, when the strain was 65%, it was increased to its maximum by 355.8% and 113.5% compared with that of pure PAA hydrogel (163.92 kPa), respectively. In addition, as induction of hybrid nanofillers, the swelling degree and water absorption behavior of composite hydrogels changed. Especially, the spherical nano-objects-doped composite hydrogel showed a lower swelling degree than others. The synergistic role from the shape of inorganic SiO2 core and alkaline component of shell was demonstrated to affect mechanical performance in PAA composite hydrogel.

Solution-Processed Bilayer Dielectrics for Flexible Low-Voltage Organic Field-Effect Transistors in Pressure-Sensing Applications.

Flexible pressure sensors based on organic field‐effect transistors (OFETs) have emerged as promising candidates for electronic‐skin applications. However, it remains a challenge to achieve low operating voltages of hysteresis‐free flexible pressure sensors. Interface engineering of polymer dielectrics is a feasible strategy toward sensitive pressure sensors based on low‐voltage OFETs. Here, a novel type of solution‐processed bilayer dielectrics is developed by combining a thick polyelectrolyte layer of polyacrylic acid (PAA) with a thin poly(methyl methacrylate) (PMMA) layer. This bilayer dielectric can provide a vertical phase separation structure from hydrophilic interface to hydrophobic interface which adjoins well to organic semiconductors, leading to improved stability and remarkably reduced leakage currents. Consequently, OFETs using the PMMA/PAA dielectrics reveal greatly suppressed hysteresis and improved mobility compared to those with a pure PAA dielectric. Using the optimized PMMA/PAA dielectric, flexible OFET‐based pressure sensors that show a record high sensitivity of 56.15 kPa−1 at a low operating voltage of −5 V, a fast response time of less than 20 ms, and good flexibility are further demonstrated. The salient features of high capacitance, good dielectric performance, and excellent reliability of the bilayer dielectrics promise a bright future of flexible sensors based on low‐voltage OFETs for wearable electronic applications.

Preparation, Characterization and Photostability of Nanocomposite Films Based on Poly(acrylic acid) and Montmorillonite

Polyacrylic acid (PAA)/clay mineral (SWy-1) nanocomposites were prepared by intercalation in solution and their photostability was evaluated. For the nanocomposite films containing 5, 10 and 20 wt % in SWy-1 mass occurred intercalation along with some clay exfoliation, while for PAA/30%SWy-1, the intercalation of PAA chains into the clay interlayers was observed. Scanning Electron Microscopy (SEM) images of the films suggested that nanocomposite films are homogeneous, indicating efficient dispersion of the polymer matrix into the SWy-1 clay. The thermal degradation temperatures of depolymerisation for the nanocomposite films were higher (362-370 °C) than pure PAA (361 °C), which means that the presence of SWy-1 clay promotes thermal stabilization.The photooxidative degradation of pure PAA and nanocomposite films was followed using Size Exclusion Chromatography (SEC). The degradation rate constant for pure PAA was higher than nanocomposite films; therefore, the increase of SWy-1concentration detained the degradation of PAA. The presence of SWy-1 clay contributes for the photostabilization of the material. SWy-1 has ability to disperse the incident light as well as also to absorb part of the UV light instead of PAA, hence minimizing the degradation rate.

Fabrication and mechanical properties of composite based on β-chitin and polyacrylic acid

Squid β-chitin has been exfoliated in aqueous acrylic acid (AA), after which a composite film of chitin microfibrils in polyacrylic acid (PAA) has been prepared by in situ polymerization of the AA. The segregated chitin fibrils in the composite are 4–6nm in diameter, with an aspect ratio >250. After drying cast films of the composites containing 1, 2 and 3% (w/w) chitin at 140°C for four hours, there was a dramatic resistance to swelling in water, in that the dried films showed only small changes in shape and properties after four hours immersed in water.The most profound impact of the reinforcement on the mechanical properties is observed at high relative humidity (RH), when the PAA is in the rubbery state. At 97.5% RH and room temperature, the elastic moduli of the composites with 1, 2 and 3% (w/w) chitin were 150, 230 and 2100MPa respectively, compared to 65MPa for pure PAA. The main contribution to the filler-reinforcing effect is the high aspect ratio of fibrils and non-covalent interactions, but the stability in water suggests the presence of chemical bonding between the PAA and chitin.

A quick responding quartz crystal microbalance sensor array based on molecular imprinted polyacrylic acids coating for selective identification of aldehydes in body odor

In present work, a novel quartz crystal microbalance (QCM) sensor array has been developed for prompt identification of primary aldehydes in human body odor. Molecularly imprinted polymers (MIP) are prepared using the polyacrylic acid (PAA) polymer matrix and three organic acids (propenoic acid, hexanoic acid and octanoic acid) as template molecules, and utilized as QCM surface coating layer. The performance of MIP films is characterized by 4-element QCM sensor array (three coated with MIP layers and one with pure PAA for reference) dynamic and static responses to target aldehydes: hexanal, heptanal, and nonanal in single, binary, and tertiary mixtures at distinct concentrations. The target aldehydes were selected subsequent to characterization of body odor samples with solid phase-micro extraction gas chromatography mass spectrometer (SPME-GC–MS). The hexanoic acid and octanoic acid imprinted PAA exhibit fast response, and better sensitivity, selectivity and reproducibility than the propenoic acid, and non-imprinted PAA in array. The response time and recovery time for hexanoic acid imprinted PAA are obtained as 5s and 12s respectively to typical concentrations of binary and tertiary mixtures of aldehydes using the static response. Dynamic sensor array response matrix has been processed with principal component analysis (PCA) for visual, and support vector machine (SVM) classifier for quantitative identification of target odors. Aldehyde odors were identified successfully in principal component (PC) space. SVM classifier results maximum recognition rate 79% for three classes of binary odors and 83% including single, binary, and tertiary odor classes in 3-fold cross validation.

UV-Vis and XRD investigation of graphite-doped poly(acrylic) acid membranes

Possible modification of the structure of poly(acrylic) acid (PAA) membranes doped with graphite was investigated by UV-Vis and XRD techniques. The pure PAA membranes were characterized by good transparency in the domain 250-700 nm, with maximum absorption at 207 nm. The absorbance of membranes increased significantly after doping with graphite. The XRD patterns of pure membranes showed a low degree of order of the polymeric matrix. Some modifications of the parameters of the ordered domains of the polymer and of the graphite appeared at high concentrations of the dopant.

Influence of Dispersing Agents on the Solubility of Perovskites in Water

In this study, solubility behavior of lead magnesium niobate (PMN) powders in water was investigated in the presence of pure polyacrylic acid and polyacrylic acid/polyethylene oxide comb polymers. Experiments were performed by measuring the solubility of PMN in terms of the concentration of Pb+2 and Mg+2 ions in supernatant as a function of pH and dispersing agent dosage. The concentrations of the metal ions in supernatant were found to be affected by the dispersant concentration, stirring time and the suspension pH. Results revealed that both dispersing agents enhance the cation dissolution from PMN surface at pH 9 due to weak (reversible) adsorption and complexation of Pb+2 and Mg+2 by carboxylate groups. On the other hand, under acidic conditions cation dissolution from PMN is inhibited and this was attributed to the strong adsorption of dispersing agents onto the powder surface and formation of a dense polymer layer.

Thermal stability and oil absorption of aluminum hydroxide treated by dry modification with different modifiers

The thermal stability, particle size and morphology and oil absorption of aluminum hydroxide(ATH) treated by dry modification with three different modifiers were investigated. The experimental results show that the thermal stability of ATH powder is markedly improved by dry modification technology with the following modifiers such as phosphoric acid, polyacrylic acid and the mixture of phosphoric acid and polyacrylic acid. The best effect comes from pure phosphoric acid, and the initial temperature for the loss of crystal water of ATH powder modified with pure polyacrylic acid can reach about 202 °C that is approximately 10 °C higher than that of ATH powder before modification. The phenomena of agglomeration and macro-aggregate badly exist in ATH powder modified with the modifiers containing phosphoric acid. The growth of particles and agglomerations of powders are not evident in ATH powder modified with pure polyacrylic acid. The oil absorption of ATH powder modified with the modifiers containing phosphoric acid is apparently larger than that of original ATH powder and ATH powder modified with pure polyacrylic acid. The oil absorption of the ATH powder modified with pure polyacrylic acid is slightly smaller than that of original ATH powder.

PH‐Sensitive Polyacrylic Acid (PAA) Hydrogels Trapped with Polysodium‐p‐Styrenesulfonate (PSS)

The preparation of a new type of semi‐interpenetration network system of polyacrylic acid (PAA) hydrogel trapped with polysodium‐p‐styrenesulfonate (PSS) is presented. The structure and response properties of PAA/PSS were investigated by Fourier transform infrared (FTIR) analysis and pH and ionic intensity stimuli‐responsive measurement. The FTIR analysis proved the successful intermingling of PSS into PAA. The swelling behavior of PAA hydrogel in an alkaline environment was improved due to the addition of PSS. As the ionic concentration in solution increased, the swelling rate of PAA decreased after adding PSS. However, the swelling velocity of the pure PAA is quicker than that of the PAA/PSS samples since the PSS will enhance the entanglement of this hydrogel network and slow down the swelling velocity. Multi‐interactions between the PAA hydrogel network and trapped PSS chains, including electrostatic repulsive interaction, entanglement interaction, ionic intensity interaction, and osmotic pressure, were proposed to explain the earlier‐mentioned experimental phenomena.

Modification of in Situ Gelling Behavior of Carbopol Solutions by Hydroxypropyl Methylcellulose

Aqueous solutions of Carbopol [polyacrylic acid (PAA)] are low viscosity acidic solutions that transform into gels upon an increase n the pH and, therefore, may be used as in situ gelling ophthalmic drug delivery systems. However, the amount of PAA required in the solution to form stiff gels upon instillation in the eye is not easily neutralized by the buffering action of tear fluid. A reduction in the PAA concentration without compromising the in situ gelling properties as well as the overall rheological behavior of the system can be achieved by adding a suitable viscosity‐enhancing polymer. The rheological properties of aqueous solutions containing PAA and hydroxypropyl methylcellulose (HPMC), a viscosity‐enhancing polymer, evaluated as a function of temperature and pH, were similar to those of pure PAA solutions; that is, both form low viscosity liquids at pH 4.0 and transform into stiff gels with plastic rheological behavior and comparable viscosities upon increasing the pH to 7.4. In addition, HPMC‐PAA gels show slow in vitro release of incorporated timolol maleate. Thus, the HPMC–PAA combination demonstrates properties suitable for formulation as a liquid ophthalmic delivery systems, which upon instillation into the cul‐de‐sac of the eye can undergo in situ phase transition to form gels capable of sustained drug release.