Polyacrylic Acid Addition Research Articles

In situ and post-synthesis polymer stabilization of ferromagnetic nanoparticles synthesized by a membrane or conventional reactor

Membrane reactors have been proven to be effective in producing nanoparticles with reduced polydispersity indices. Recently, our group has incorporated this technology into the synthesis of ferromagnetic nanoparticles. In the initial phase, we conducted post-synthesis stabilization experiments to assess the performance of various polymeric agents. Polyacrylic acid (PAA) was chosen because of its notable affinity for the functional groups on the nanoparticle surface. Subsequently, in situ stabilization experiments were conducted using a membrane reactor, with variations in PAA addition flow rates ranging from 0.33 to 1.5 mL/min and maturation times in an ultrasonic bath ranging from 0.5 to 2 h. The samples were characterized in terms of their hydrodynamic diameter, polydispersity, and Z-potential. Notably, the smallest particle size was achieved at the intermediate point with a PAA flow rate of 0.66 mL/min. However, the influence of maturation time did not follow a predictable pattern; the most favorable characteristics, based on the analyzed variables, were observed at 1.5 and 2 h.

Metal ion and ultrasonication assisted assembling chiral nematic coatings towards humidity-responsive and anti-counterfeiting

Humidity-responsive sensitive materials have garnered considerable interest in a wide range of humidity sensors and information encryption applications. However, developing an eco-friendly sensitive material with mechanical robustness and response efficiency remains a significant challenge. Herein, we report a facile and smart strategy for assembling humidity-responsive cellulose nanocrystal (CNC)/polyacrylic acid (PAA)-Na iridescent coatings, assisted by metal ion regulation and ultrasonication. Owing to the enhanced electrostatic attraction between the positive charge (Na+) and negative charge (OSO3− and COO−), as well as the abundant hydrogen bonding networks, PAA addition can be as high as 50 wt%, which enables the design of CNC/PAA-Na iridescent coatings with excellent toughness and strength. Moreover, CNC/PAA-Na iridescent coatings possess a precise chiral nematic arrangement with a tunable helical pitch and a high g-factor above 0.5. The chiral nematic characteristics and absorption capacities are related to the humidity-responsive performance. Conditioned under variable humidity stimuli, CNC/PAA-Na iridescent coatings exhibit sensitive humidity-responsive behavior. In particular, the CNC/PAA50-Na/S iridescent coating achieves a wider humidity-responsive wavelength of 144 nm with a relative humidity (RH) above 43%. Interestingly, the CNC/PAA-Na iridescent coatings could regulate the transmitted colors under cross-polarization. Based on chiral nematic triggered by humidity, an “RH-rotation angle-color” ternary colorimetric system is established, which highlights the potential of CNC/PAA-Na iridescent coatings regarding sensitive humidity-response and information encryption.

PVA-Based Hydrogels Loaded with Diclofenac for Cartilage Replacement.

Polyvinyl alcohol (PVA) hydrogels have been widely studied for cartilage replacement due to their biocompatibility, chemical stability, and ability to be modified such that they approximate natural tissue behavior. Additionally, they may also be used with advantages as local drug delivery systems. However, their properties are not yet the most adequate for such applications. This work aimed to develop new PVA-based hydrogels for this purpose, displaying improved tribomechanical properties with the ability to control the release of diclofenac (DFN). Four types of PVA-based hydrogels were prepared via freeze-thawing: PVA, PVA/PAA (by polyacrylic acid (PAA) addition), PVA/PAA+PEG (by polyethylene glycol (PEG) immersion), and PVA/PAA+PEG+A (by annealing). Their morphology, water uptake, mechanical and rheological properties, wettability, friction coefficient, and drug release behavior were accessed. The irritability of the best-performing material was investigated. The results showed that the PAA addition increased the swelling and drug release amount. PEG immersion led to a more compact structure and significantly improved the material’s tribomechanical performance. The annealing treatment led to the material with the most suitable properties: besides presenting a low friction coefficient, it further enhanced the mechanical properties and ensured a controlled DFN release for at least 3 days. Moreover, it did not reveal irritability potential for biological tissues.

Polymer-Colloid Complexes Based on Cationic Imidazolium Amphiphile, Polyacrylic Acid and DNA Decamer.

The solution behavior and physicochemical characteristics of polymer–colloid complexes based on cationic imidazolium amphiphile with a dodecyl tail (IA-12) and polyacrylic acid (PAA) or DNA decamer (oligonucleotide) were evaluated using tensiometry, conductometry, dynamic and electrophoretic light scattering and fluorescent spectroscopy and microscopy. It has been established that PAA addition to the surfactant system resulted in a ca. 200-fold decrease in the aggregation threshold of IA-12, with the hydrodynamic diameter of complexes ranging within 100–150 nm. Electrostatic forces are assumed to be the main driving force in the formation of IA-12/PAA complexes. Factors influencing the efficacy of the complexation of IA-12 with oligonucleotide were determined. The nonconventional mode of binding with the involvement of hydrophobic interactions and the intercalation mechanism is probably responsible for the IA-12/oligonucleotide complexation, and a minor contribution of electrostatic forces occurred. The latter was supported by zeta potential measurements and the gel electrophoresis technique, which demonstrated the low degree of charge neutralization of the complexes. Importantly, cellular uptake of the IA-12/oligonucleotide complex was confirmed by fluorescence microscopy and flow cytometry data on the example of M-HeLa cells. While single IA-12 samples exhibit roughly similar cytotoxicity, IA-12–oligonucleotide complexes show a selective effect toward M-HeLa cells (IC50 1.1 µM) compared to Chang liver cells (IC50 23.1 µM).

Fabrication of an Organo-Fluoride–Free Hydrophobic Film Using the Sol-Gel Method by Factors Screening and Poly-Acrylic Acid Addition

Improving silica film’s contact angle (CA) using tetraethoxysilane (TEOS) and iso-butyltrimethoxysilane (iso-BTMS) by the sol-gel method without adding organo-fluoride substances is of interest. Five factors, namely type of solvent, molar ratio and amounts of TEOS and iso-BTMS, mixing intensity, sol aging time, and presence and absence of poly-acrylic acid (PAA), were assessed to improve the static water CA of the film and its surface quality. Results revealed that when ethanol was used as the dissolving solvent and after adding initial iso-BTMS and TEOS concentrations of 0.0270 and 0.0194 mol/L (molar ratio = 1.39), respectively, without sonication and adding PAA/TEOS weight ratio of 0.029, then the maximum static CA of the film reached 147°, a nearly super-hydrophobic surface. Under given conditions, long-term film durability was observed, and the added PAA prevented the formation of nonhomogeneous film surfaces caused by the highly clustering aggregation of silanols under high pH conditions.

Effect of polyacrylic acid addition on structure, magnetic and adsorption properties of manganese ferrite nanoparticles

A facile hydrothermal method is used to synthesize manganese ferrite nanoparticles with the addition of polyacrylic acid (PAA). PAA addition does not largely decrease the magnetic performance of MnFe2O4 nanoparticles, but highly enhance the adsorption properties for methylene blue (MB) dye. It demonstrates that the concentration of negative –COO− groups in the solution determines the adsorption capacity of MnFe2O4 nanoparticles for MB. The maximum MB adsorption capacity was 44.9mg/g, and the adsorption kinetics of MB match well with the pseudo-second-order model. To reveal the influence mechanism of PAA addition on the properties of manganese ferrite nanoparticles, two different synthetic routes are designed by changing the adding method of PAA with the different mass ratio of PAA to MnFe2O4. Here, the second synthetic route is easier and simpler to operate than the first one. Moreover, with the PAA addition, the adsorption capacity for the samples synthesized by synthetic route 2 increases by 43.4%, which is much higher than that (28.6%) of the samples synthesized by synthetic route 1. Synthetic route 1 reveals that PAA acting as a reducing agent participates in the reaction on the formation of MnFe2O4 ferrites. Herein, the Fe3+ ions bound by PAA chains are reduced to Fe2+ ions. This work clearly points out that the PAA addition contributes to enhancing the adsorption properties of ferrite nanoparticles for organic dye, which provides guidance to the adsorption study on the similar adsorbents for the removal of organic contaminant from the wastewater.

Effect of Polyacrylic Acid Addition on Rheology of SiC‐Al2O3‐ZrO2(3Y) Mixed Suspensions

A suspension with good rheology and high stability is crucial for slip casting and gelcasting technology. However, a mixed suspension from two or more different powders usually has bad rheology because of the easy agglomeration of mixed powders caused by the attractive force between the powders with heterocharges. We studied the surface modification of the each single‐component powders (SiC, Al2O3, ZrO2(3Y) powders) and the SiC‐Al2O3‐ZrO2(3Y) mixed powders to increase the repulsive force by adjusting the pH value and adding polyacrylic acid (PAA) as dispersant. The PAA addition effects on the SiC‐Al2O3‐ZrO2(3Y) mixture were investigated in terms of zeta potential, pH range for heterocharge region, dispersion of the mixed powders and rheology of the mixed slurry based on the study of each unary suspensions. The results show that before surface modification the SiC‐Al2O3‐ZrO2(3Y) mixed powders were agglomerated severely because they were in the heterocharge region with a broad pH range from 3.5 to 8.25, while after surface modification (pH = 10.5, PAA = 0.8wt%) the heterocharge region was narrowed with a relatively narrower pH range from 2.6 to 3.7. The mixed powders with homocharges were dispersed well because of the great electrostatic repulsive force and steric hindrance offered by PAA and the mixed suspensions had favorable rheology.

Influence of polyacrylic acid on rheology of SiC suspension and mechanical properties of densified SiC

Abstract Addition of polyacrylic acid (PAA) to a 30 vol% SiC suspension with Al 2 O 3 (2.5 mass% to SiC) and Y 2 O 3 (2.5 mass% to SiC) decreased the viscosity of the suspension at pH 5.0. The prepared suspension was consolidated by filtration through a gypsum mold. The green compact was hot-pressed to 98.7–99.3% theoretical density at 1800 °C under a pressure of 39 MPa for 2 h in an Ar flow. The sintering mechanism was discussed based on the analysis of the shrinkage curve of SiC compacts during the hot-pressing. The grain size of hot-pressed SiC decreased by PAA addition in the suspension. PAA addition improved the Weibull modulus of flexural strength and fracture toughness of SiC at a small expense of average strength. The measured mechanical properties were as follows: average strength 647 MPa, Weibull modulus 6.6, fracture toughness 5.0 MPa m 1/2 and Vickers hardness 24.5 GPa for the SiC hot-pressed without PAA, and average strength 615 MPa, Weibull modulus 8.2, fracture toughness 5.8 MPa m 1/2 and Vickers hardness 24.8 GPa for the SiC hot-pressed with PAA.

Effects of PAA additive and temperature on morphology of calcium carbonate particles

Calcium carbonate particles with various shapes were prepared by the reaction of sodium carbonate with calcium chloride in the absence and presence of a polyacrylic acid (PAA) at 25°C and 80°C, respectively. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The effects of pH, temperatures, aging time and concentration of PAA and CaCO 3 on the crystal form and morphologies of the as-prepared CaCO 3 were investigated. The results show that pH, temperatures, concentration of PAA and CaCO 3 are important parameters for the control of morphologies of CaCO 3. Various crystal morphologies of calcite, such as, plates, rhombohedras, rectangles, ellipsoids, cubes, etc. can be obtained depending on the experimental conditions. Especially, the monodispersed cubic calcite particles can be produced by PAA addition at 80°C. Moreover, higher temperature is beneficial to the formation of monodispersed cubic or rectangular calcite particles. This research may provide new insight into the control of morphologies of calcium carbonate and the biomimetic synthesis of novel inorganic materials.