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https://www.readbyqxmd.com/read/28440385/temporal-viscosity-modulations-driven-by-a-ph-sensitive-polymer-coupled-to-a-ph-changing-chemical-reaction
#1
D M Escala, A P Muñuzuri, A De Wit, J Carballido-Landeira
The Formaldehyde-Sulfite (FS) and the Formaldehyde-Sulfite-Gluconolactone (FSG) systems are examples of complex chemical reactions accompanied by well-controlled variations in pH. While the FS system exhibits a clock behavior, in the FSG reaction, this mechanism is coupled with the hydrolysis of the gluconolactone which gives the possibility to show large temporal oscillations of pH in an open reactor. In this work, we show how these reactive systems, due to their organic nature, can be coupled with pH sensitive polymers, particularly with polyacrylic acid (PAA) to trigger temporal changes of viscosity...
April 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28432970/insights-into-key-factors-controlling-go-stability-in-natural-surface-waters
#2
Yang Gao, Xuemei Ren, Xiaoli Tan, Tasawar Hayat, Ahmed Alsaedi, Changlun Chen
The effects of pH, cations (Na(+), K(+), Mg(2+), Ca(2+) and Al(3+)), and anions (Cl(-), HCO3(-), HPO4(2-) and SO4(2-)) on graphene oxide (GO) stability were investigated to address the current limitations in the knowledge regarding the stability of GO in natural surface water and its underlying mechanism. The threshold values of cations that destabilize GO were obtained and affected by both pH and anions. By employing elemental mapping and studying the effects of polyacrylic acid (PAA) on GO sedimentation and the re-dispersion of GO aggregates, we find that the GO aggregates induced by Na(+) and K(+) via electric double layer suppression and by Ca(2+) and Al(3+) via strong complxing are difficult to re-disperse completely...
April 11, 2017: Journal of Hazardous Materials
https://www.readbyqxmd.com/read/28427665/combined-ultrasonic-and-gamma-irradiation-to-prepare-tio2-pet-g-paac-fabric-composite-for-self-cleaning-application
#3
Mohamed Mohamady Ghobashy
The grafting of polyacrylic acid (PAAc) onto the fabric of Poly(ethyleneterephthalate) (PET) was loaded with TiO2 by a mixture sonication of TiO2 dispersed in AAc dissolved in acetone solvent. Ultrasonic irradiation was utilized as a tool for a good dispersion of TiO2 onto the PET fabric. The grafted PET fabrics with acrylic acid AAc monomer were successfully obtained using gamma-ray induced graft polymerization, the degree of grafting PET-g-PAAc fiber was 105%. The chemical compositions and crystal structure of grafted TiO2@PET-g-PAAc fabrics were characterized by ATR-FTIR and XRD...
July 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28419800/ph-reversible-encapsulation-of-oppositely-charged-colloids-mediated-by-polyelectrolytes
#4
Yong Guo, Bas G P van Ravensteijn, Chris H J Evers, Willem K Kegel
We report the first example of reversible encapsulation of micron-sized particles by oppositely charged submicron smaller colloids. The reversibility of this encapsulation process is regulated by pH-responsive poly(acrylic acid) (PAA) present in solution. The competitive adsorption between the small colloids and the poly(acrylic acid) on the surface of the large colloids plays a key role in the encapsulation behavior of the system. pH offers an experimental knob to tune the electrostatic interactions between the two oppositely charged particle species via regulation of the charge density of the poly(acrylic acid)...
April 24, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28411637/armored-enzyme-nanohybrids-and-their-catalytic-function-under-challenging-conditions
#5
Omkar V Zore, Rajeswari M Kasi, Challa V Kumar
Synthesis and characterization of highly stable and functional bienzyme-polymer triads assembled on layered graphene oxide (GO) are described here. Glucose oxidase (GOx) and horseradish peroxidase (HRP) were used as model enzymes and polyacrylic acid (PAA) as model polymer to armor the enzymes. PAA-armored GOx and HRP covalent conjugates were further protected from denaturation by adsorption onto GO nanosheets. Structure and morphology of this enzyme-polymer-nanosheet hybrid biocatalyst (GOx-HRP-PAA/GO) were confirmed by agarose gel electrophoresis, zeta potential, circular dichroism, and transmission electron microscopy...
2017: Methods in Enzymology
https://www.readbyqxmd.com/read/28371515/spherical-polyelectrolyte-brushes-as-a-novel-platform-for-paramagnetic-relaxation-enhancement-and-passive-tumor-targeting
#6
Qin Zhu, Zhenyu Yuan, Weiqiao Qian, Yuanyuan Li, Zhiqiang Qiu, Weijun Tang, Jie Wang, Yun Ding, Aiguo Hu
A novel platform for the development of highly efficient magnetic resonance imaging (MRI) contrast agents has been demonstrated. New contrast agents are designed and produced through electrostatic self-assembly of cationic gadolinium(III) complexes onto anionic spherical polyelectrolyte brushes (SPB). The structurally well-defined SPB are composed of polystyrene core and polyacrylic acid brush layer, where numerous binding sites and confined microenvironments are available for the embedment of the gadolinium(III) contrast agents...
April 3, 2017: Advanced Healthcare Materials
https://www.readbyqxmd.com/read/28368667/one-step-formation-of-lipid-polyacrylic-acid-calcium-carbonate-nanoparticles-for-co-delivery-of-doxorubicin-and-curcumin
#7
Jianqing Peng, Shintaro Fumoto, Hirotaka Miyamoto, Yi Chen, Naotaka Kuroda, Koyo Nishida
A doxorubicin (Dox) and curcumin (Cur) combination treatment regimen has been widely studied in pre-clinical research. However, the nanoparticles developed for this combination therapy require a consecutive drug loading process because of the different water-solubility of these drugs. The present study provides a strategy for the 'one-step' formation of nanoparticles encapsulating both Dox and Cur. We took advantage of polyacrylic acid (PAA) and calcium carbonate (CaCO3) to realise a high drug entrapment efficiency and pH-sensitive drug release using a simplified preparation method...
April 3, 2017: Journal of Drug Targeting
https://www.readbyqxmd.com/read/28358160/highly-stiff-yet-elastic-microcapsules-incorporating-cellulose-nanofibrils
#8
Gilad Kaufman, Shomeek Mukhopadhyay, Yekaterina Rokhlenko, Siamak Nejati, Rostislav Boltyanskiy, Youngwoo Choo, Michael Loewenberg, Chinedum O Osuji
Microcapsules with high mechanical stability and elasticity are desirable in a variety of contexts. We report a single-step method to fabricate such microcapsules by microfluidic interfacial complexation between high stiffness cellulose nanofibrils (CNF) and an oil-soluble cationic random copolymer. Single-capsule compression measurements reveal an elastic modulus of 53 MPa for the CNF-based capsule shell with complete recovery of deformation from strains as large as 19%. We demonstrate the ability to manipulate the shell modulus by the use of polyacrylic acid (PAA) as a binder material, and observe a direct relationship between the shell modulus and the PAA concentration, with moduli as large as 0...
April 12, 2017: Soft Matter
https://www.readbyqxmd.com/read/28350963/gd-dots-with-strong-ligand-water-interaction-for-ultrasensitive-magnetic-resonance-renography
#9
Xiao-Yu Zheng, Kai Zhao, Jinglong Tang, Xin-Yu Wang, Lin-Dong Li, Nai-Xiu Chen, Yan-Jie Wang, Shuo Shi, Xiaodong Zhang, Sivakumar Malaisamy, Ling-Dong Sun, Xiaoying Wang, Chunying Chen, Chun-Hua Yan
Magnetic resonance imaging contrast agents with both significantly enhanced relaxivity and minimal safety risk are of great importance for sensitive clinical diagnosis, but have rarely been reported. Herein, we present a simple strategy to improve relaxivity by introducing surface ligands with strong interaction to water molecules. As a proof of concept, NaGdF4 nanoparticles (NPs) capped by poly(acrylic acid) (PAA) show superior relaxivity to those capped by polyethylenimine and polyethylene glycol, which is attributed to the strong hydrogen-bond capacity of PAA to water molecules as revealed by theoretical calculation...
April 25, 2017: ACS Nano
https://www.readbyqxmd.com/read/28345148/fast-self-healing-of-polyelectrolyte-multilayer-nanocoating-and-restoration-of-super-oxygen-barrier
#10
Yixuan Song, Kevin P Meyers, Joseph Gerringer, Ramesh K Ramakrishnan, Mohammad Humood, Shuang Qin, Andreas A Polycarpou, Sergei Nazarenko, Jaime C Grunlan
A self-healable gas barrier nanocoating, which is fabricated by alternate deposition of polyethyleneimine (PEI) and polyacrylic acid (PAA) polyelectrolytes, is demonstrated in this study. This multilayer film, with high elastic modulus, high glass transition temperature, and small free volume, has been shown to be a super oxygen gas barrier. An 8-bilayer PEI/PAA multilayer assembly (≈700 nm thick) exhibits an oxygen transmission rate (OTR) undetectable to commercial instrumentation (<0.005 cc (m(-2) d(-1) atm(-1) ))...
March 27, 2017: Macromolecular Rapid Communications
https://www.readbyqxmd.com/read/28327587/in-situ-characterization-of-the-initial-effect-of-water-on-molecular-interactions-at-the-interface-of-organic-inorganic-hybrid-systems
#11
Sven Pletincx, Lena Trotochaud, Laura-Lynn Fockaert, Johannes M C Mol, Ashley R Head, Osman Karslıoğlu, Hendrik Bluhm, Herman Terryn, Tom Hauffman
Probing initial interactions at the interface of hybrid systems under humid conditions has the potential to reveal the local chemical environment at solid/solid interfaces under real-world, technologically relevant conditions. Here, we show that ambient pressure X-ray photoelectron spectroscopy (APXPS) with a conventional X-ray source can be used to study the effects of water exposure on the interaction of a nanometer-thin polyacrylic acid (PAA) layer with a native aluminum oxide surface. The formation of a carboxylate ionic bond at the interface is characterized both with APXPS and in situ attenuated total reflectance Fourier transform infrared spectroscopy in the Kretschmann geometry (ATR-FTIR Kretschmann)...
March 22, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28322540/rapid-recovery-double-cross-linking-hydrogel-with-stable-mechanical-properties-and-high-resilience-triggered-by-visible-light
#12
Longxiang Zhu, Jianhui Qiu, Eiichi Sakai, Kazushi Ito
The designed tough hydrogels, depending on energy dissipation mechanism, possess excellent biocompatibility, stimuli-responsiveness, and outstanding mechanical properties. However, the application of hydrogels is greatly limited in actuators and sensors for the lack of instantaneous recovery and resilience. In this work, we synthesized a double cross-linking poly(acrylic acid) hydrogel via a simple, one-pot, visible-light-trigger polymerization, with carboxymethyl cellulose as initiator and the first cross-linker, N,N'-methylene bis(acrylamide) (MBA) as the second cross-linker...
April 5, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28320261/rheological-and-sensory-properties-of-hydrophilic-skin-protection-gels-based-on-polyacrylates
#13
Agnieszka Kulawik-Pióro, Joanna Kurpiewska, Agnieszka Kułaszka
INTRODUCTION: With the current increases in occupational skin diseases, literature data attesting the decreasing efficiency of barrier creams with respect to the manufacturer's declarations and legal regulations granting skin protection gels for employees, research is required to analyse and evaluate the recipes used for hydrophilic skin protection gels based on polyacrylates. METHODS: This study investigated the rheological properties, pH and sensory perception of hydrophilic barrier gels based on polyacrylates...
April 10, 2017: International Journal of Occupational Safety and Ergonomics: JOSE
https://www.readbyqxmd.com/read/28316987/selective-removal-of-hemoglobin-from-blood-using-hierarchical-copper-shells-anchored-to-magnetic-nanoparticles
#14
Youxun Liu, Yaokun Wang, Mingyang Yan, Juan Huang
Hierarchical copper shells anchored on magnetic nanoparticles were designed and fabricated to selectively deplete hemoglobin from human blood by immobilized metal affinity chromatography. Briefly, CoFe2O4 nanoparticles coated with polyacrylic acid were first synthesized by a one-pot solvothermal method. Hierarchical copper shells were then deposited by immobilizing Cu(2+) on nanoparticles and subsequently by reducing between the solid CoFe2O4@COOH and copper solution with NaBH4. The resulting nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy, and vibrating sample magnetometry...
2017: BioMed Research International
https://www.readbyqxmd.com/read/28274489/re-mineralizing-dentin-using-an-experimental-tricalcium-silicate-cement-with-biomimetic-analogs
#15
Xin Li, Jan De Munck, Kumiko Yoshihara, Mariano Pedano, Kirsten Van Landuyt, Zhi Chen, Bart Van Meerbeek
OBJECTIVES: To characterize the re-mineralization potential of an experimental zirconium oxide (ZrO2) containing tricalcium silicate (TCS) cement, TCS 50, with the incorporation of biomimetic analogs at demineralized dentin. METHODS: Class-I cavities were prepared in non- carious human third molars. The dentin cavities were demineralized using a pH-cycling protocol, involving 50 cyclic immersions in pH-4.8 and pH-7 baths for 0.5h and 2.5h, successively. The cavities were filled with TCS 50 with/without biomimetic analogs (3% polyacrylic acid, 8% sodium trimetaphosphate) being added to the mixed TCS 50 cement prior to application...
March 5, 2017: Dental Materials: Official Publication of the Academy of Dental Materials
https://www.readbyqxmd.com/read/28263023/gold-nanoparticles-based-solid-phase-microextraction-coatings-for-determining-organochlorine-pesticides-in-aqueous-environmental-samples
#16
Adrián Gutiérrez-Serpa, Priscilla Rocío-Bautista, Verónica Pino, Francisco Jiménez-Moreno, Ana I Jiménez-Abizanda
The use of solid-phase microextraction coatings based on gold nanoparticles was investigated, focusing the attention on the preparation of nanoparticles with nonclassical reduction agents of HAuCl4 such as gallic acid and H2 O2 , rather than the conventional sodium citrate. All nanoparticles were characterized by diode array spectroscopy, whereas novel nanoparticles prepared with gallic acid and H2 O2 were also characterized by microscopic techniques. Solid-phase microextraction coatings were prepared with a layer-by-layer approach...
March 6, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28256055/solvent-free-method-for-the-determination-of-lignin-derived-phenols-in-sediments
#17
Mayara Pinto, Morgana Frena, Luiz Augusto Dos Santos Madureira
A solvent-free method that uses headspace solid-phase microextraction and gas chromatography with flame ionization detection is proposed for the determination of lignin-derived phenols in sediments. The extraction and derivatization conditions for the simultaneous analysis of acetosyringone, acetovanillone, syringaldehyde, vanillin, ferulic acid, syringic acid, vanillic acid, p-hydroxybenzoic acid and p-coumaric acid were optimized using a central composite design. After optimization, the best results were obtained with the following conditions: exposure of the polyacrylate fiber to the headspace with 60 μL of N,O-bis(trimethylsilyl)trifluoroacetamide as a derivatizing agent for 15 min and then extraction in the headspace of 100 mg of sediment (previously spiked with lignin-derived phenols) for 35 min...
March 3, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/28252022/simultaneous-removal-of-atrazine-and-copper-using-polyacrylic-acid-functionalized-magnetic-ordered-mesoporous-carbon-from-water-adsorption-mechanism
#18
Yaoyu Zhou, Fengfeng Zhang, Lin Tang, Jiachao Zhang, Guangming Zeng, Lin Luo, Yuanyuan Liu, Pei Wang, Bo Peng, Xiaocheng Liu
Highly efficient simultaneous removal of atrazine and Cu(II) was accomplished using synthesized polyacrylic acid-functionalized magnetic ordered mesoporous carbon (P-MMC) as compared to magnetic ordered mesoporous carbon (MMC) and ordered mesoporous carbon (OMC). The mutual effects and interactive mechanism of their adsorption onto P-MMC were investigated systematically by binary, preloading and thermodynamic adsorption procedures. In both binary and preloading systems, the adsorption of atrazine was inhibited to some extent by the presence of Cu(II) because of selective recognition and direct competition, but the presence of atrazine had negligible effect on Cu(II) desorption...
March 2, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28248076/multifunctional-theranostic-agent-of-cu2-oh-po4-quantum-dots-for-photoacoustic-image-guided-photothermal-photodynamic-combination-cancer-therapy
#19
Wei Guo, Zhenyu Qiu, Chongshen Guo, Dandan Ding, Tianchan Li, Fei Wang, Jianzhe Sun, Nannan Zheng, Shaoqin Liu
Image-guided phototherapy is considered to be a prospective technique for cancer treatment because it can provide both oncotherapy and bioimaging, thus achieving an optimized therapeutic efficacy and higher treatment accuracy. Compared to complicated systems with multiple components, using a single material for this multifunctional purpose is preferable. In this work, we strategically fabricated poly(acrylic acid)- (PAA-) coated Cu2(OH)PO4 quantum dots [denoted as Cu2(OH)PO4@PAA QDs], which exhibit a strong near-infrared photoabsorption ability...
March 22, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28230077/cartilage-like-electrostatic-stiffening-of-responsive-cryogel-scaffolds
#20
G S Offeddu, I Mela, P Jeggle, R M Henderson, S K Smoukov, M L Oyen
Cartilage is a structural tissue with unique mechanical properties deriving from its electrically-charged porous structure. Traditional three-dimensional environments for the culture of cells fail to display the complex physical response displayed by the natural tissue. In this work, the reproduction of the charged environment found in cartilage is achieved using polyelectrolyte hydrogels based on polyvinyl alcohol and polyacrylic acid. The mechanical response and morphology of microporous physically-crosslinked cryogels are compared to those of heat-treated chemical gels made from the same polymers, as a result of pH-dependent swelling...
February 23, 2017: Scientific Reports
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