PAA Solution Research Articles

Suppression of aerosol dispersion by highly viscoelastic poly(acrylic acid)- and poly(ethylene oxide)-based coolants during bone drilling

Bone drilling in neurosurgical, dental, and orthopedic procedures, combined with the use of coolants, generates a dispersion of bone particles, coolants, and blood aerosols in the air. This poses the threat of airborne transmission of infectious diseases between patients and medical practitioners. Highly viscoelastic polymeric poly(acrylic acid) (PAA) and poly(ethylene oxide) (PEO) solutions of various concentrations were used as coolants during bone drilling at different mass flow rates to suppress aerosol generation, thereby mitigating the threat of cross-infection. The results revealed that the PAA and PEO solutions provide less advection than water and a comparable cooling performance. However, excessive viscoelasticity of PEO causes the fluid to rise along the cutting burr (the Weissenberg effect), thereby reducing the cooling coverage area. In contrast, slightly lower viscoelasticity of PEO results in a high cooling coverage area. The cooling coverage area is smaller for the PAA at 20 ml/min because the corresponding PAA solution easily swirls or splashes away from the drilling location. However, at 80 ml/min, the supplied PAA solution sufficiently cools the drilling area, despite the loss through splashing. The numbers of atomized droplets of water and the PAA and PEO solutions were quantified and compared to investigate the degree of aerosol formation and dispersion. The solution with the strongest viscoelasticity most significantly suppressed aerosolization and produced the fewest dispersed aerosol droplets during bone drilling.

Crosslinking and Swelling Properties of pH-Responsive Poly(Ethylene Glycol)/Poly(Acrylic Acid) Interpenetrating Polymer Network Hydrogels.

This study investigates the crosslinking dynamics and swelling properties of pH-responsive poly(ethylene glycol) (PEG)/poly(acrylic acid) (PAA) interpenetrating polymer network (IPN) hydrogels. These hydrogels feature denser crosslinked networks compared to PEG single network (SN) hydrogels. Fabrication involved a two-step UV curing process: First, forming PEG-SN hydrogels using poly(ethylene glycol) diacrylate (PEGDA) through UV-induced free radical polymerization and crosslinking reactions, then immersing them in PAA solutions with two different molar ratios of acrylic acid (AA) monomer and poly(ethylene glycol) dimethacrylate (PEGDMA) crosslinker. A subsequent UV curing step created PAA networks within the pre-fabricated PEG hydrogels. The incorporation of AA with ionizable functional groups imparted pH sensitivity to the hydrogels, allowing the swelling ratio to respond to environmental pH changes. Rheological analysis showed that PEG/PAA IPN hydrogels had a higher storage modulus (G') than PEG-SN hydrogels, with PEG/PAA-IPN5 exhibiting the highest modulus. Thermal analysis via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated increased thermal stability for PEG/PAA-IPN5 compared to PEG/PAA-IPN1, due to higher crosslinking density from increased PEGDMA content. Consistent with the storage modulus trend, PEG/PAA-IPN hydrogels demonstrated superior mechanical properties compared to PEG-SN hydrogels. The tighter network structure led to reduced water uptake and a higher gel modulus in swollen IPN hydrogels, attributed to the increased density of active network strands. Below the pKa (4.3) of acrylic acid, hydrogen bonds between PEG and PAA chains caused the IPN hydrogels to contract. Above the pKa, ionization of PAA chains induced electrostatic repulsion and osmotic forces, increasing water absorption. Adjusting the crosslinking density of the PAA network enabled fine-tuning of the IPN hydrogels' properties, allowing comprehensive comparison of single network and IPN characteristics.

Charge transfer-driven enhanced lithium extraction using poly(acrylic) acid-modified layered double hydroxide

This study presents an advanced strategy for developing a novel poly(acrylic) acid-modified layered double hydroxide (PAA@LDH) for enhanced lithium adsorption. The optimal modification conditions include the use of a 2.5 % PAA solution in deionized water, an LDH powder dosage of 90 mL/g, and direct mixing at 333 K. Under these conditions, additional negatively charged functional groups were introduced into the material structure, thereby improving charge transfer, increasing electron cloud density, and lowering equipotential charge, as determined by DFT calculations. Consequently, the modified adsorbent exhibited a substantial rise in lithium adsorption capacity, increasing from 2.08 mg/g to 3.41 mg/g in produced water with low lithium concentration. Adsorption kinetics were rapid, reaching equilibrium within 40 min, and the adsorption behavior conformed to the Langmuir isotherm model. Besides, the adsorbent exhibited excellent selectivity for Li+ ions and maintained its performance at approximately 3.40 mg/g over seven cycles when regenerated under neutral conditions. The findings establish a robust framework for designing innovative adsorbent systems for lithium recovery from aqueous sources like produced water.

WATER-RESPONSIVE SELF-HEALING MEMBRANE MODIFIED WITH POLYETHYLENEIMINE (PEI)/POLY (ACRYLIC ACID) (PAA)

The self-healing membrane has received substantial research attention in recent years due to its ability to overcome the difficulty in detecting the exact damage location of the membrane at a microscopic level. The healing effect of a self-healable membrane often requires the help of an external stimulus. This study reported the fabrication of a water-responsive self-healing membrane using polyethyleneimine (PEI)/poly(acrylic acid) (PAA) coated on polyethersulfone (PES) membrane via layer-by-layer (LbL) method. Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray (EDX) were performed to observe the successful attachment of PEI and PAA onto the PES surface. The topographical analysis was performed using scanning electron microscopy (SEM) to visualize the healing performance. Apart from the instrumental analysis, pure water flux (PWF) was conducted to quantify the healing efficiency of the membrane. The best self-healing performance of the fabricated PEI/PAA self-healing membrane at 5.0 mg/mL concentration of PEI and PAA solutions displayed a healing efficiency of 70 % after being immersed into distilled water for 24 hours, compared to the concentrations of 1.0 mg/mL (19.8 %) and 3.0 mg/mL (34.3 %). This could be attributed to the higher amounts of PAA to form hydrogen bonds with surrounding water molecules, and subsequently promotes healing performance as hydrogen bonds are the basis for the self-healing process. This study proposes a newly develop water-stimulus PEI/PAA self-repairing membrane which contributes to the energy-efficient membrane filtration process.

Colorless and transparent polyimide nanocomposites using organically modified montmorillonite and mica

In this study, we introduce a method for replacing the glass used in existing display electronic materials, lighting, and solar cells by synthesizing a colorless and transparent polyimide (CPI) film with excellent mechanical properties and thermal stability using a combination of new monomers. Poly(amic acid) (PAA) was synthesized using dianhydride 4,4′-biphthalic anhydride (BPA) and diamine 2,2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (AHP). Various contents of organically modified montmorillonite (MMT) and mica were dispersed in PAA solution through solution intercalation, and then CPI hybrid films were prepared through multi-step thermal imidization. The organoclays synthesized to prepare CPI hybrid films were Cloisite 93A (CS-MMT) and hexadimethrine-mica (HM-Mica) based on MMT and mica, respectively. In particular, the diamine monomer AHP containing a –OH group was selected to increase the dispersibility and compatibility between the hydrophilic clays and the CPI matrix. To demonstrate the characteristics of CPI, the overall polymer structure was bent and a strong electron withdrawing –CF3 group was used as a substituent. The thermomechanical properties, morphology of clay dispersion, and optical transparency of the CPI hybrid films were investigated and compared according to the type and content of organoclays. Two types of organoclays, CS-MMT and HM-Mica, were dispersed in a CPI matrix at 1 to 7 wt%, respectively. In electron microscopy, most of the clays were uniformly dispersed in a plate-like shape of less than 20 nm at a certain critical content of the two types of organoclays, but agglomeration of the clays was observed when the content was higher than the critical content. Hybrids using HM-Mica had better thermomechanical properties and hybrids containing CS-MMT had better optical transparency.

Inactivation of Desiccation-Resistant Salmonella on Apple Slices Following Treatment with ε-Polylysine, Sodium Bisulfate, or Peracetic Acid and Subsequent Dehydration

Salmonella is capable of surviving dehydration within various foods, such as dried fruit. Dried fruit, including apple slices, have been the subject of product recalls due to contamination with Salmonella. A study was conducted to determine the fate of Salmonella on apple slices, following immersion in three antimicrobial solutions (viz., ε-polylysine [epsilon-polylysine or EP], sodium bisulfate [SBS], or peracetic acid [PAA]), and subsequent hot air dehydration. Gala apples were aseptically cored and sliced into 0.4 cm thick rings, bisected, and inoculated with a five-strain composite of desiccation-resistant Salmonella, to a population of 8.28 log CFU/slice. Slices were then immersed for 2 min in various concentrations of antimicrobial solutions, including EP (0.005, 0.02, 0.05, and 0.1%), SBS (0.05, 0.1, 0.2, and 0.3%), PAA (18 or 42 ppm), or varying concentrations of PAA + EP, and then dehydrated at 60°C for 5 h. Salmonella populations in positive control samples (inoculated apple slices washed in sterile water) declined by 2.64 log after drying. In the present study, the inactivation of Salmonella, following EP and SBS treatments, increased with increasing concentrations, with maximum reductions of 3.87 and 6.20 log (with 0.1 and 0.3% of the two compounds, respectively). Based on preliminary studies, EP concentrations greater than 0.1% did not result in lower populations of Salmonella. Pretreatment washes with either 18 or 42 ppm of PAA inactivated Salmonella populations by 4.62 and 5.63 log, respectively, following desiccation. Combining PAA with up to 0.1% EP induced no greater population reductions of Salmonella than washing with PAA alone. The addition of EP to PAA solutions appeared to destabilize PAA concentrations, reducing its biocidal efficacy. These results may provide antimicrobial predrying treatment alternatives to promote the reduction of Salmonella during commercial or consumer hot air drying of apple slices.

Enhancement of selective SiGe dissolution through facilitated surface oxidation by formation of hydroxyl radicals in peracetic acid solution

Herein, we investigate the selective oxidation and dissolution behavior of SiGe over Si using mixtures of HF, H2O2, CH3COOH, and CH3COOOH (peracetic acid, PAA). We observe a significantly higher dissolution rate for SiGe compared to Si in the PAA solution. This difference can be attributed to more rapid and vigorous oxidation of the SiGe surface compared to that of the Si surface. We introduce a novel method to further enhance the selective dissolution of SiGe by controlling the formation of hydroxyl radicals in the PAA solution. When the formation of hydroxyl radicals is enhanced, the SiGe dissolution rate and selectivity significantly increase from 212 nm/min and 111 to 793 nm/min and 225, respectively. The selective etching of the SiGe layers is also achieved on vertically stacked multilayer SiGe/Si trench structures at an etching factor of 95:1. The increase in the SiGe dissolution rate and selectivity over Si can be attributed to the effective oxidation of the SiGe surface by hydroxyl radicals without causing surface roughening in either SiGe or Si. Based on the results, we propose a mechanism for the selective oxidation and dissolution of SiGe in PAA solution, with and without the enhancement of hydroxyl radicals.

INVESTIGATION OF MODIFIED POLYACRYLAMIDE FOR OIL DISPLACEMENT

At present, the use of surfactants and water-soluble polyelectrolytes, which act as stabilizing and selective agents, is inextricably linked with the successful solution of the technological issues in the world of chemical, oil and other industries. The purpose of the work is to synthesize and study the physicochemical properties of modified polyacrylamide with gossypol resin and further crosslinking in the presence of potassium persulfate and sodium sulphate to displace oil. Methods. To establish the spectral characteristics of the modified PAA, IR spectra have been taken on an IR-Fourier spectrometer. For the structural-elemental composition (SEM), a Jeol JSM-6490l V electron microscope has been used. The viscosity of modified PAA solutions has been measured in a Ubellode capillary viscometer with a hanging level. Results and discussion. The studies, carried out by the authors of the study of the colloid-chemical properties of polymer composites, allow us to conclude that the reagents obtained during the hydrolysis of vat residues of fatty acids distillation with sodium hydroxide with further cross-linking in the presence of potassium persulfate and sodium sulphate have good surfaceactive and emulsifying properties, which is important when displacing oil from layers. The surface tension of polymer compositions has been studied. With an increase in the concentration of the solution, the surface tension decreases, i.e., the surface activity increases. Conclusion. The research results show that the injection of a polymer reagent solution can increase the oil displacement efficiency by 6-7%.

Suppression of cross-infection in actual dental office using viscoelastic polyacrylate solution as a handpiece coolant

In the present work, aqueous solutions of NaPAA [poly (sodium acrylate)] or PAA [polyacrylic acid] are used as the coolants for a dental handpiece to evaluate their suppressive effect on the aerosolization and bacteria (Staphylococcus epidermidis) transmission in an actual dental environment. Both polymer solutions significantly suppressed the formation of aerosols (<50 μm) and droplets (50–100 μm). The suppression effect was stronger at higher concentrations. The 10 and 20 wt. % of viscous Newtonian solutions of low-molecular weight NaPAA were much less effective in disintegration suppression than the viscoelastic 1 and 2 wt. % PAA solutions. The latter was capable of complete suppression of disintegration, forming instead long liquid threads attached to the rotating bur and settling down underneath. The suppression efficiency of the 2 wt. % PAA solution stems from significant elastic forces in it which prevent drop detachment. In the case of water used as a coolant, the bacterial spread was observed through aerosol, droplets, and splatter. The bacterial spread by large splatters was inversely proportional to the distance from the rotating bur. The spread of aerosols significantly occurred in the direction that the handpiece was facing, and multiple airborne aerosols settled on the wall rather than on the floor. On the other hand, the viscoelastic aqueous 2 wt. % PAA solution suppressed bacterial spread, regardless of the distance or direction.

Kök Kanal Tedavisinde Kullanılan Farklı İrrigasyon Solüsyonlarının Yüzey Gerilimlerinin Karşılaştırılması

Amaç: Bu çalışmanın amacı kök kanal tedavisinde kullanılan farklı irrigasyon solüsyonlarının yüzey gerilimi değerlerini karşılaştırmaktır. Gereç ve Yöntem: %5.25 NaOCl, %9 HEBP, %2 PAA, %17 EDTA, %5.25 NaOCl + %9 HEBP, %5.25 NaOCl + %2 PAA, %5.25 NaOCl + %17 EDTA solüsyonlarının yüzey gerilimi değerleri damla şekli analiz cihazı DSA30 (Kruss, Hamburg, Almanya) ile ölçüldü. Her irrigasyon solüsyonu için 10 ayrı ölçüm yapıldı. Veriler mj/m2 cinsinden kaydedildi. Grupların ortalama ve standart sapma değerleri, tek yönlü ANOVA ve Bonferroni ve Tukey Çoklu Karşılaştırma Testleri yapılarak istatistiksel olarak değerlendirildi. Bulgular: En yüksek yüzey gerilim değerini %5.25 NaOCl + %2 PAA solüsyonu, en düşük değeri %9 HEBP solüsyonu gösterdi. %5.25 NaOCl+ %2 PAA grubunun yüzey gerilimi, %5.25 NaOCl, %9 HEBP, %2 PAA, %5.25 NaOCl+ %9 HEBP gruplarından istatistiksel olarak daha yüksekti (p<0.05). %5.25 NaOCl, %9 HEBP, %2 PAA ve %5.25 NaOCl+ %9 HEBP grupları arasında istatistiksel açıdan herhangi bir fark bulunmadı (p>0.05). Sonuç: Test edilen irrigasyon solüsyonları arasında %9 HEBP solüsyonu en düşük yüzey gerilimine sahipti.

Water-Absorbing Bioadhesive Poly(Acrylic Acid)/Polyvinylpyrrolidone Complex Sponge for Hemostatic Agents.

Poly(acrylic acid) (PAA) is a water-soluble synthetic polymer with tissue-adhesive properties. When PAA is mixed with polyvinylpyrrolidone (PVP) in water, it forms a water-insoluble precipitate that neither swells nor adheres to tissues. We developed a novel solid/solution interface complexation method to obtain a water-swellable PAA/PVP complex. First, PAA solution was dried up in a vessel to form a film. The PAA film was then immersed in an aqueous PVP solution to obtain a highly swollen PAA/PVP hydrogel. Heat drying of the hydrogel yielded a transparent film, while freeze-drying the hydrogel provided a soft sponge. Both the PAA/PVP film and sponge could be re-swelled by water to obtain a bioadhesive gel. A relatively larger specific surface area of the sponge than that of the film led to a more rapid swelling and water absorption behavior and quick adhesion to tissues. The addition of hyaluronic acid (HA) improved the mechanical characteristics of the sponges. PAA/PVP/HA sponges had low cytotoxicity, and they exhibited high hemostatic efficiency in clinical studies after dialysis treatment or tooth extraction, even in patients on antithrombotic drugs. Such bioadhesive materials consisting of low-toxicity polymers have a high potential for use in medical hemostatic devices.

Preparation and characterization of photo‐decomposable ester‐containing semi‐alicyclic polyimide alignment layers for potential applications in in‐plane switching thin‐film transistor liquid crystal display devices

AbstractPoly(amic acid)s (PAAs) alignment agents have been prepared from the alicyclic dianhydrides, including 1,2,3,4‐cyclobutanetetracarboxylic dianhydride (CBDA, I), 1,3‐dimethyl‐1,2,3,4‐cyclobutanetetracarboxylic dianhydride (DMCBDA, II), and ester‐linked aromatic diamines, including 4‐aminophenyl‐4′‐aminobenzoate (APAB, a) and bis(4‐aminophenyl)terephthalate (BPTP, b), respectively. The derived PAAs, including PAA‐Ia (CBDA‐APAB), PAA‐Ib (CBDA‐BPTP), and PAA‐IIa (DMCBDA‐APAB) exhibited the preferable molecular weights, while the PAA‐IIb (DMCBDA‐BPTP) showed the low one due to the low polymerization reactivity both for the DMCBDA dianhydride and the BPTP diamine. All the PAA solutions except PAA‐IIb were adopted as the alignment components to fabricate liquid crystal (LC) minicells with a mode of in‐plane switching (IPS). The polyimides (PI) alignment layers derived from the thermal dehydration reaction of the PAA precursors at 230°C for 30 min showed good alignments effects to the LC molecules, which exhibited the pretilt angles (θp) from 0.09 to 0.15° after being exposed by the linear polarized ultraviolet light sources with the wavelength of 254 nm. In addition, the PI alignment layers afforded good optoelectronic features to the minicells, including the voltage holding ratio values over 97% at room temperature, and the residual direct circuit voltages lower than 1.0 V. The anchoring energy results indicated that the PI‐IIa (DMCBDA‐APAB) alignment layer showed the highest interaction with the LC molecules, and thus exhibited the highest threshold voltage (Vth) in the voltage‐transmittance (V‐T) measurements for the minicells.

The suspending appearance of poly(acrylic acid)‐based rheology modifier in high‐content surfactant: The effect of polymer structure and molecular weight on the rheological properties of the complex systems

AbstractThe “all in one” multifunctional and concentrated daily chemical products are required by the market, such as the long‐term release of anti‐bacterial, medical, or perfume agents. These functions mainly rely on the microcapsules, which could encapsulate these functional and unstable molecules, and then release them in the long term. To stabilize these functional solid particles in a high‐content surfactant, it is necessary to add a suspending rheological modifier. The poly(acrylic acid) (PAA)‐based rheology modifier is one of the most common additives in the industry of daily chemicals, for thickening or suspending. In this paper, linear PAA, and branched PAA polymers (Carbomer 941 and Carbomer 940) were selected to study the suspending ability of PAA‐based rheology modifier in high‐content surfactant and to investigate the effect of PAA polymer structure and Mw on the complex solution's rheological properties. The yield and viscosity test of the complex solutions of linear PAA and high‐content surfactant revealed that the addition of linear PAA could lead to lower yield stress and viscosity, and failed to suspend the polystyrene (PS) model microspheres due to its smaller mean square radius of gyration. The branched PAA polymer, Carbomer 940 and Carbomer 941 were more stable than the linear PAA in these two kinds of surfactant. More specifically, Carbomer 940 with a higher Mw, would exhibit higher yield stress and viscosity than Carbomer 941 with a lower Mw in nonionic surfactant alcohol polyoxyethylene ether (AEO) solvent with content less than 5 wt%. When the content was higher than 5 wt%, Carbomer 941 presented higher yield stress and viscosity than Carbomer 940, and successfully suspended PS microspheres in the 20 wt% AEO solution. This could depend on the polymer chain's elongation state of these two PAA‐based branched rheology modifiers. The same trend happened in the appearance of Carbomer 940 and Carbomer 941 in alcohol ether sulphate (AES) solution. However, the electrostatic repulsive force between the AES and PAA‐based rheology modifier could further make the polymer chain curl up and restrain the suspending ability in a lower content surfactant solution. Therefore, this fundamental research could guide the application of the anionic polyelectrolytes in the concentrated daily chemical product for stable suspending particles.

Development and characterization of ion-releasing fiber-reinforced flowable composite

ObjectiveThis study aimed to develop and characterize an ion-releasing experimental fiber-reinforced flowable composite (Bio-SFRC) and dentin treatment solution made of poly(acrylic acid) (PAA) with a high molecular weight. In addition we also evaluated the interface structure and mineralization potential between the Bio-SFRC and dentin. MethodsSome mechanical properties (flexural properties and fracture toughness) of Bio-SFRC in comparison with commercial inert (G-aenial Flo X) and ion-releasing materials (ACTIVA-BioActive Base/Liner and Fuji II LC) were assessed (n = 8/group). Calcium-release at different time-points was measured during the first six weeks by using a calcium-ion selective electrode. Surface analysis of composites after being stored in simulated body fluid (SBF) was investigated by using SEM/EDS. Dentin disks (n = 50) were prepared from extracted sound teeth and demineralization was simulated by acid etching. SEM/EDS was used to evaluate the microstructure of dentin on the top surface and at interface with composites after being stored in SBF. ResultsBio-SFRC showed higher fracture toughness (1.6 MPa m1/2) (p < 0.05) compared to Flo X (1.2 MPa m1/2), ACTIVA (1 MPa m1/2) and Fuji II LC (0.8 MPa m1/2). Accumulative calcium release after six weeks from Bio-SFRC (15 mg/l) was higher than other tested ion-releasing materials (≈ 6 mg/l). Mineralization was clearly seen at the interface between treated dentin and Bio-SFRC. None of the commercial tested materials showed signs of mineralization at the interface and dentinal tubules remained open.Significance.Developing such reinforced ion-releasing flowable composite and PAA solution might offer the potential for mineralization at the interface and inside the organic matrix of demineralized dentin.

Impact of gas ultrafine bubbles on the efficacy of commonly used antimicrobials for apple washing

AbstractUltrafine bubble (UFB) technology is a novel tool in food safety with potential to improve the efficacy of antimicrobials during produce washing. This research investigated the impact of incorporating gas (air and CO2) UFBs on the potency of chlorine (Cl2; 100 and 200 ppm) and peracetic acid (PAA; 40 and 80 ppm) antimicrobial solutions against Escherichia coli O157:H7 and Listeria monocytogenes on inoculated Gala apples. Apples were dip inoculated with either E. coli or L. monocytogenes, and dried at room temperature for 1 hr. Apples were then treated by dipping into Cl2 or PAA solutions with or without UFBs (CO2 or air) for 1 or 2 min. Apples were then transferred into bags containing Dey‐Engley neutralizing broth, and hand massaged for 90 s. Log reductions for respective antimicrobial treatments were calculated by subtracting post‐antimicrobial treatment bacterial populations from the initial bacterial populations on inoculated apples. Incorporation of CO2 UFBs in antimicrobial solutions resulted in significantly greater E. coli and L. monocytogenes reductions (2.1 and 2.4 Log CFU/apple, respectively) on apples compared to solutions without UFBs (1.4 and 1.9 Log CFU/apple, respectively). However, incorporation of air UFBs resulted in similar log reductions of E. coli and L. monocytogenes (1.9 and 2.2 Log CFU/apple, respectively) on apples compared to antimicrobials with CO2 UFBs and without UFBs. The 2 min treatment time for various antimicrobials resulted in significantly greater L. monocytogenes reductions (2.4 Log CFU/apple) compared to 1 min (2.0 Log CFU/apple), but no differences were observed for E. coli.

A facile method to fabricate high performance PVA/PAA-AS hydrogel via the synergy of multiple hydrogen bonding and Hofmeister effect

Hydrogels are widely used in biomedical engineering, which often require matched mechanical properties to meet specific demands. Recently, numerous research studies have contributed to tissue engineering hydrogels by soaking strategies to obtain designed properties. Herein, a strategy to fabricate poly(vinyl alcohol)/poly(acrylic acid)-ammonium sulfate (PVA/PAA-AS) hydrogel by successively soaking an aqueous PAA solution and (NH4)2SO4 solution based on the synergy of multiple hydrogen bonding and Hofmeister effect is reported, which exhibits remarkable comprehensive mechanical properties: rigidity (elastic modulus: 0.73.6 ), strength at break (tensile stress: 3.212.0 ; strain 320650%), and toughness (fracture energy: 4.530.0 ). Besides, PVA/PAA-AS hydrogel with unique spring-like microstructure exhibited super-resilience in 30% strain range by energy-transforming mechanism. Compared with pure PVA hydrogel, PVA/PAA-AS hydrogel has the equal excellent cytocompatibility. Therefore, PVA/PAA-AS hydrogel with high strength, modulus, toughness, super-resilience and excellent biocompatibility has potential applications in the soft tissue engineering field such as muscles, tendons, and ligaments.

Facile activation of flower-like polyimide-based carbon electrodes for high-performance supercapacitors

In this work, the flower-like polyimide (PI) particles were prepared via a solvothermal method using poly(amic acid) (PAA) solution derived from 4,4′-oxydianiline (ODA) and cyclobutane-1,2,3,4-tetracarboxylicdianhydride (CBDA). Then, the corresponding carbon materials were obtained by further pyrolysis. The effects of the concentration of PAA solution and carbonization temperature on the properties of carbon materials were investigated. Moreover, in order to increase the electrochemical performance, the flower-like carbon particles were further activated by KOH, and the amount of KOH was optimized. The structures and properties of the final flower-like carbon particles were characterized by FTIR, SEM, XPS, XRD, Raman, nitrogen adsorption-desorption and electrochemical tests. When the mass ratio of carbon materials to KOH was 1:3, the activated flower-like carbon particles A-PIODA-1/3 showed a high specific surface area of 1498 m2 g−1, a specific capacitance of 313.4 F g−1 at 0.5 A g−1 and a high-rate capability of 230.0 F g−1 at 10 A g−1. The assembled symmetrical supercapacitor (SC) showed a maximum energy density of 28.08 Wh kg−1, coupled with a power density of 500.0 W kg−1. After 20,000 cycles at a current density of 1 A g−1, the SC exhibited an excellent cycling stability with a 99.6 % capacitance retention rate. Therefore, the activated flower-like carbon particles can be simply prepared, which could be expected to be used as a preferable electrode material for energy storage applications.

Comparison of Properties of Colorless and Transparent Polyimide Nanocomposites Containing Chemically Modified Nanofillers: Functionalized-Graphene and Organoclay.

Poly(amic acid) (PAA) was synthesized from dianhydride 4,4-(4,4-isopropylidenediphenoxy)bis(phthalic anhydride) and diamine bis [4-(3-aminophenoxy) phenyl] sulfone. Colorless and transparent polyimide (CPI) hybrid films were synthesized through thermal imidization after dispersing nanofillers using an intercalation method in a PAA solution. C16-GS and C16-MMT, in which hexadecylamine (C16) was substituted on graphene sheet (GS) and montmorillonite (MMT), respectively, were used as nanofillers to reinforce the CPI hybrid films. These two nanofillers were admixed in varying loadings of 0.25 to 1.00 wt%, and the morphology, thermal properties, and optical transparency of the hybrid films were investigated and compared. The results suggest that the thermal properties of the CPI hybrid films can be improved by adding only a small amount of nanofiller. Transmission electron microscopy results of the CPI hybrid film containing two types of fillers suggested that the fillers were well dispersed in the nano-size in the matrix polymer; however, some of the fillers were observed as agglomerated particles above the critical concentration of 0.50 wt%.

γ-Irradiation crosslinking of graphene oxide/cellulose nanofiber/poly (acrylic acid) hydrogel as a urea sensing patch

Poly (acrylic acid) (PAA) nanocomposite hydrogel was fabricated as a sensing patch for non-invasive dual detection of urea in sweat. The hydrogel was prepared by γ-irradiation crosslinking of PAA solution incorporated with graphene oxide (GO) and cellulose nanofiber (CNF). With high water-sorption capacity and transparency, the hydrogel was suitable to accommodate coloring reagents and enzymes for colorimetric sensing of urea in sweat. The colorimetric sensor exhibited vivid color change towards the increase of urea concentration in a linear range of 40–80 mM covering a cut-off value (60 mM) for chronic kidney disease (CKD) indication. Furthermore, the hydrogel could be directly applied as a substrate for direct quantitation of urea in sweat by laser desorption ionization mass spectroscopy (LDI-MS). While CNF improved the mechanical properties of the hydrogel, GO played a key role in enhancing laser desorption ionization of urea in LDI-MS and increased the hydrogel functionalities. LDI-MS verified that GO/CNF/PAA hydrogel could act as a direct matrix for promoting urea ionization and these results corresponded well with the colorimetric sensor. Hence, this hydrogel patch might be a potential material to be applied in non-invasive and dual-detection of CKD in medical diagnosis.

Potential of hydrophobic paper-based sorptive phase prepared by in-situ thermal imidization for the extraction of methadone from oral fluid samples

Paper-based sorptive phases (PSPs) are functional planar materials with a demonstrated potential in analytical sample preparation. This article describes the synthesis of a polyimide coated paper by an in-situ imidization at a high temperature. Polyimides (PI) are synthesized in two subsequent steps where a hydrophilic polymer, in this case, poly(amic acid) (PAA), is formed as an intermediate product. PAA is finally transformed into hydrophobic PI by thermal curing at 180 °C. The synthesis of PI-paper takes advantage of this two-step procedure. In the first stage, a segment of filter paper is immersed into an aqueous PAA solution. After the solvent evaporation, the paper is heated at 180 °C for 1 h inducing the formation of the hydrophobic PI over the cellulose fibers. Infrared spectroscopy has been used to characterize the synthesized materials by defining a coverage factor F. The hydrophobicity of the materials has been studied using an aqueous methylene blue solution as a marker. To fully demonstrate the usefulness of the material in the sample preparation field, the extraction of methadone from oral fluid (OF) samples has been considered as a model analytical problem. The main variables affecting the synthesis (PAA concentration on the precursor solution and number of dips) and the extraction (elution and extraction times) have been fully evaluated. Working under the optimum conditions, a limit of quantification of 9 µg/L, intraday and interday precision better than 14.6%, and accuracy in the range of 87–108% were obtained.