Showing papers on "Methacrylic acid published in 2016"

Atom Transfer Radical Polymerization of Methacrylic Acid: A Won Challenge.

Abstract: Polymerization of acidic monomers is one of the biggest challenges for atom transfer radical polymerization (ATRP). An intramolecular cyclization reaction leading to the loss of the C–X chain-end functionality was found to be the main reason for the partial termination of the growing polymer chains. Three approaches were used to overcome this problem: using Cl as the chain-end halogen, lowering the pH (to 0.9), and increasing polymerization rate. Methacrylic acid (MAA) was polymerized by both electrochemically mediated ATRP and supplemental activator and reducing agent ATRP up to high conversion (>90%), in t ≤ 4 h at 25 °C, using inexpensive and nontoxic reagents (NaCl, diluted HCl, water). Control over molecular weight (MW) dispersity was satisfactory, and MWs were in agreement with theoretical values. The “livingness” of the process was confirmed by an electrochemical switch, used to repeatedly and periodically deactivate/reactivate growing chains.

Synthesis of sensitive hybrid polymer microgels for catalytic reduction of organic pollutants

Abstract: Multiresponsive tercopolymer microgel poly( N -isopropyl acrylamide- co -methacrylic acid- co -2-hydroxyethyl methacrylate) was synthesized by free radical emulsion polymerization. The silver and gold nanoparticles were homogeneously dispersed in polymer network by in-situ chemical reduction method at 10 and 40 °C using sodium borohydride as reducing agent. FT-IR spectroscopy confirms the microgel synthesis and existing of metal nanoparticles inside the polymer network. Temperature and pH sensitivity on particle size of the microgel particles was investigated by dynamic light scattering. Transmission electron microscopy analysis showed that the size of Ag and Au nanoparticles is 13 and 7 nm, respectively. The catalytic activity of hybrid microgels was studied for the reduction of aqueous solutions of 4-nitrophenol, congo red and methylene blue as model reactions.

Alternating Sequence Control for Carboxylic Acid and Hydroxy Pendant Groups by Controlled Radical Cyclopolymerization of a Divinyl Monomer Carrying a Cleavable Spacer.

Abstract: By utilizing features of the hemiacetal ester (HAE) bond: easy formation from vinyl ether and carboxylic acid and easy cleavage into different functional groups (-COOH and -OH), we achieved control of the alternating sequence of two functional pendant groups of a vinyl copolymer. Methacrylate- and acrylate-based vinyl groups were connected through HAE bonds to prepare a cleavable divinyl monomer, which was cyclo-polymerized under optimized conditions in a ruthenium-catalyzed living radical polymerization. Subsequent cleavage of the HAE bonds in the resultant cyclo-pendant led to a copolymer consisting of alternating methacrylic acid and 2-hydroxyethyl acrylate units as analyzed by 13C NMR spectroscopy. The alternating sequence of -COOH and -OH pendants specifically provided a lower critical solution temperature (LCST) in an ether solvent, which was not observed with the random copolymer of same composition ratio.

An effective method for the synthesis of yolk–shell magnetic mesoporous carbon-surface molecularly imprinted microspheres

Abstract: This study aims to immobilise molecularly imprinted polymers (MIPs) on the surface of yolk–shell magnetic mesoporous carbon (Fe3O4@void@C) spheres for phthalate ester (PAE) recognition through an effective route. To link MIPs to Fe3O4@void@C spheres, carboxyl-modified yolk–shell magnetic mesoporous carbon (Fe3O4@void@C–COOH) was synthesised by first oxidising Fe3O4@void@C with H2O2, and MIPs were subsequently grafted on the surface of Fe3O4@void@C–COOH by a surface polymerisation method with diisononyl phthalate (DINP), methacrylic acid (MAA) and ethylene glycol dimethacrylate (EGDMA) as template molecule, functional monomer and cross-linker, respectively. The structure and morphology of the synthesised materials were characterised by XRD, TEM, SEM, FT-IR, N2 sorption and magnetic susceptibility measurements. The synthesis conditions for the formation of Fe3O4@void@C–COOH were systematically investigated. It was observed that the chemical modification of Fe3O4@void@C is highly influenced by the type of oxidant, the concentration of H2O2, oxidation temperature and time. The adsorption isotherm and kinetics of Fe3O4@void@C-MIPs showed that Fe3O4@void@C-MIPs possessed good recognition, fast adsorption rates (approximately 20 min to reach equilibrium) and high adsorption capacities (569.2 mg g−1) toward PAEs, which were ascribed to their uniformity and monodispersity. In addition, Fe3O4@void@C-MIPs exhibited excellent reusability for the adsorption of PAEs over six adsorption–desorption cycles.

High surface-area amidoxime-based polymer fibers co-grafted with various acid monomers yielding increased adsorption capacity for the extraction of uranium from seawater

Abstract: Uranium is dissolved in the ocean at a uniform concentration of 3.34 ppb, which translates to approximately 4-5 billion tons of uranium. The development of adsorbents that can extract uranium from seawater has been a long term goal, but the extremely dilute uranium concentration along with the competition of other metal salts (which are at higher concentrations) has hindered the development of an economical adsorption process. Several acid monomers were co-grafted with acrylonitrile (AN) to help increase the hydrophilicity of the adsorbent to improve access to the metal adsorption sites. Grafting various acid monomers on PE fibers was found to significantly affect the uranium adsorption in simulated seawater in the following order: acrylic acid (AA) < vinyl sulfonic acid (VSA) < methacrylic acid (MAA) < itaconic acid (ITA) < vinyl phosphonic acid (VPA). Interestingly, the uranium adsorption capacity significantly increased when Mohr's salt was added with acrylic acid, most likely due to the reduction of co-polymerization of the monomers. When testing under more realistic conditions, the acid-grafted PE fiber adsorbents were exposed to natural seawater (more dilute uranium), the uranium adsorption capacity increased in the following order: MAA < AA (Mohr's salt) < VSA < ITA (Mohr's salt) < ITA < VPA, which agreed well with the simulated seawater results. Characterization of the adsorbents indicated that the increase in uranium adsorption capacity with each acid monomer was related to higher grafting of AN and therefore a higher conversion to amidoxime (AO).

Study on the cross-linked molecularly imprinted poly(methacrylic acid) and poly(acrylic acid) towards selective adsorption of diuron

Abstract: In the present study new molecularly imprinted adsorbents based on poly(methacrylic acid) and poly(acrylic acid) have been synthesized, characterized and evaluated as selective materials for the adsorption of diuron. Morphological, textural data and the presence of functional groups in the polymer have been evaluated by means of SEM, nitrogen adsorption–desorption assays and FT-IR, respectively. Two functional monomers were evaluated for the MIP synthesis, methacrylic acid (MIP MAA ) and acrylic acid (MIP AA ), and the first one showed higher selectivity and better adsorption towards diuron in the presence of competitor molecules, carbofuran and 2,4-D. The experimental adsorption isotherm of diuron has been obtained at pH 7.0 in phosphate buffer (0.05 mol L − 1 ):acetonitrile (1:2, v / v ) medium and equilibrium time of 180 min. The respective maximum adsorption capacities (MAC) of MIP MAA and MIP AA were found to be 14.58 and 7.32 mg g − 1 . One should note that MAC of MIP AA and its respective blank polymer (NIP AA ) was very similar to each other, while for the MIP MAA its MAC was significantly higher (14.58 mg g − 1 ) than the MAC of NIP MAA (6.12 mg g − 1 ). Such result demonstrates the great influence of monomer on the adsorption and selectivity of MIP. Adsorption kinetic data were well fitted to pseudo-first-order and intraparticle diffusion models, while the adsorption isotherms showed good fit to the isotherm of Langmuir–Freundlich for two sites (LF-2) and one site (LF-1), but the former one allowed insight into the adsorption mechanism with more details.

Molecularly Imprinted Polymer Nanoparticles for Formaldehyde Sensing with QCM.

Abstract: Herein, we report on molecularly imprinted polymers (MIPs) for detecting formaldehyde vapors in air streams. A copolymer thin film consisting of styrene, methacrylic acid, and ethylene glycol dimethacrylate on quartz crystal microbalance (QCM) yielded a detection limit of 500 ppb formaldehyde in dry air. Surprisingly, these MIPs showed specific behavior when tested against a range of volatile organic compounds (VOCs), such as acetaldehyde, methanol, formic acid, and dichloromethane. Despite thus being a suitable receptor in principle, the MIPs were not useful for measurements at 50% humidity due to surface saturation by water. This was overcome by introducing primary amino groups into the polymer via allyl amine and by changing the coating morphology from thin film to nanoparticles. This led to the same limit of detection (500 ppb) and selectivity as before, but at the real-life conditions of 50% relative humidity.

High porosity, responsive hydrogel copolymers from emulsion templating

Abstract: Hydrogels, three-dimensional hydrophilic polymer network structures, can absorb many times their dry weight in water. PolyHIPEs are highly porous polymers synthesized within high internal phase emulsions (HIPEs). Here, the water uptakes in novel hydrogel polyHIPE copolymers of hydroxyethyl methacrylate (HEMA, a non-ionic monomer) and methacrylic acid (MAA, an ionic monomer) were investigated. The PHEMA-based polyHIPE had a density of 0.14 g cm−3, void diameters of 50–100 µm and a void-dominated Fickian water uptake of around 10.4 g g−1. The polyHIPE density increased, and the porous structure became less polyHIPE-like, with increasing MAA content, reflecting a reduction in the stability of the HIPE. The water uptake increased with increasing pH for all the copolymers and the water absorption mechanism changed from Fickian at pH 2 to anomalous, dominantly case II, at pH 10. The maximum uptake of 18.2 g g−1 at pH 10, for a HEMA to MAA mass ratio of 1/1, was ascribed to hydrogel-swelling-driven void expansion. The hydrogel's absorptive and responsive properties were amplified by the polyHIPE's porous structure. These results demonstrate that the compositions of hydrogel polyHIPE copolymers can be designed to enhance their water uptake. © 2015 Society of Chemical Industry

Chitosan-Based Lead Ion-Imprinted Interpenetrating Polymer Network by Simultaneous Polymerization for Selective Extraction of Lead(II)

Abstract: In this study, we report the synthesis of a Pb(II) ion-imprinted interpenetrating polymer network (II-IPN) by simultaneous polymerization for selective extraction of Pb(II) from printed-circuit-board (PCB) recycling unit wastewater. Initially, a polymer network was synthesized by polymerization of methacrylic acid (monomer) and ethylene glycol dimethacrylate (cross-linker) and a second polymer network by chitosan (complexing monomer) and tetraethyl orthosilicate (cross-linker). The chemical structure and morphology of the II-IPN were analyzed using Fourier transform infrared, field-emission scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The interaction of the functionality in the II-IPN with Pb(II) through chelation was studied by X-ray photoelectron spectroscopy analysis. The maximum adsorption capacities for II-IPN and nonimprinted interpenetrating polymer network were 37.5 and 10.3 mg g–1, respectively. The largest selectivity coefficient for Pb(II) in the ...

Simultaneous catalytic degradation/reduction of multiple organic compounds by modifiable p(methacrylic acid-co-acrylonitrile)–M (M: Cu, Co) microgel catalyst composites

Abstract: We prepared poly(methacrylic acid-co-acrylonitrile) (p(MAc-co-AN)) microgels by inverse suspension polymerization, and converted the nitrile groups into amidoxime groups to obtain more hydrophilic amidoximated poly(methacrylic acid-co-acrylonitrile) (amid-p(MAc-co-AN)) microgels. Amid-microgels were used as microreactors for in situ synthesis of copper and cobalt nanoparticles by loading Cu(II) and Co(II) ions into microgels from their aqueous metal salt solutions and then converted to their corresponding metal nanoparticles (MNPs) by treating the loaded metal ions with sodium borohydride (NaBH4). The characterization of the prepared microgels and microgel metal nanoparticle composites was carried out by SEM, TEM and TG analysis. The amounts of metal nanoparticles within microgels were estimated by AAS measurements by dissolving the MNP entrapped within microgels by concentrated HCl acid treatment. Catalytic performances of the prepared amid-p(MAc-co-AN)–M (M: Cu, Co) microgel composites were investigated by using them as catalysts for the degradation of cationic and anionic organic dyes such as eosin Y (EY), methylene blue (MB) and methyl orange (MO), and for the reduction of nitro aromatic pollutants like 2-nitrophenol (2-NP) and 4-nitrophenol (4-NP) to their corresponding amino phenols. Here, we also report for the first time, the simultaneous degradation/reduction of MB, EY and 4-NP by amid-p(MAc-co-AN)–Cu microgel composites. Different parameters affecting the reduction rates such as metal types, the amount of catalysts, temperature and the amount of reducing agent were investigated.

Bucky Papers of Poly(Methyl Methacrylate-co-Methacrylic acid)/Polyamide 6 and Graphene Oxide-Montmorillonite

Abstract: Novel poly(methyl methacrylate-co-methacrylic acid) (PMMAMA) and polyamide 6 (PA-6) blend was reinforced with graphene oxide (GO) and montmorillonite-modified GO (GO-MMT). In this way, two series of composites were prepared with varying GO and GO-MMT content. PA-6 was in situ polymerized and the effect of filler addition on molecular weight was studied using GPC. In the case of GO-MMT system, the lowering in molecular weight was more pronounced (Mn ∼ 15 × 103 gmol−1). The thermal stability of PMMAMA/PA-6/GO-MMT 0.5–5 system was found higher than PMMAMA/PA-6/GO 0.5–5. PHHR of PMMAMA/PA-6/GO-MMT was decreased from 317 to 214 kW/m2 with 0.5–5 wt% loading.

Antibacterial Activity of Silver Nanoparticle-Loaded Soft Contact Lens Materials: The Effect of Monomer Composition

Abstract: Purpose: In the present work, the effect of monomer composition on silver nanoparticles’ (SNPs) binding capacity of hydrogels was investigated and their antibacterial efficacy was evaluated.Materials and methods: Three series of poly-hydroxyethyl methacrylate (HEMA) hydrogels were prepared using methacrylic acid (MAA), methacrylamide (MAAM), and 4-vinylpyridine (4VP) as co-monomers, and ethylene glycol dimethacrylate (EGDMA) as cross-linker. SNPs binding capacity of hydrogels was evaluated in different concentrations (2, 10, and 20 ppm). In vitro antibacterial activity of SNP-loaded hydrogels was studied against Pseudomonas aeruginosa (P. aeruginosa) isolated from patients’ eyes. Then, inhibitory effect of hydrogels in biofilm formation was evaluated in the presence of Staphylococcus epidermidis (S. epidermidis) (DSMZ 3270).Results: Our data indicated that poly(HEMA-co-MAA-co-EGDMA) had superior binding affinity for SNPs in comparison with other hydrogels. All SNP-loaded hydrogels demonstrated exc...

Preparation of novel pH‐sensitive nanocomposites based on ionic‐liquid modified montmorillonite for colon specific drug delivery system

Abstract: An ionic liquid monomer, 3-methyl-1-[2-(2-methyl-acryloxy)-ethyl]-imidazolium chloride, was synthesized through the quaternization of N-methylimidazole and 2-chloroethyl methacrylate. This ionic liquid monomer intercalated into the montmorillonite layers and subsequently copolymerized with methacrylic acid. The organic–inorganic composite was characterized by FTIR, XRD, SEM, and EDX to study their structure and properties. Naproxen as a model drug was entrapped in these pH-sensitive positively charged nano carriers and the in vitro release profiles were established separately in both enzyme-free simulated gastric and intestinal fluids (SGF, pH 1) and (SIF, pH 7.4) respectively. It was observed that the drug release percentages in SIF were higher; hence the prepared nanocomposite could be considered as a suitable carrier for colon specific drug delivery. POLYM. COMPOS., 2014. © 2014 Society of Plastics Engineers

Polymer Encapsulation of an Amorphous Pharmaceutical by initiated Chemical Vapor Deposition for Enhanced Stability.

Abstract: The usage of amorphous solids in practical applications, such as in medication, is commonly limited by the poor long-term stability of this state, because unwanted crystalline transitions occur. In this study, three different polymeric coatings are investigated for their ability to stabilize amorphous films of the model drug clotrimazole and to protect against thermally induced transitions. For this, drop cast films of clotrimazole are encapsulated by initiated chemical vapor deposition (iCVD), using perfluorodecyl acrylate (PFDA), hydroxyethyl methacrylate (HEMA), and methacrylic acid (MAA). The iCVD technique operates under solvent-free conditions at low temperatures, thus leaving the solid state of the encapsulated layer unaffected. Optical microscopy and X-ray diffraction data reveal that at ambient conditions of about 22 °C, any of these iCVD layers extends the lifetime of the amorphous state significantly. At higher temperatures (50 or 70 °C), the p-PFDA coating is unable to provide protection, while the p-HEMA and p-MAA strongly reduce the crystallization rate. Furthermore, p-HEMA and p-MAA selectively facilitate a preferential alignment of clotrimazole and, interestingly, even suppress crystallization upon a temporary, rapid temperature increase (3 °C/min, up to 150 °C). The results of this study demonstrate how a polymeric coating, synthesized directly on top of an amorphous phase, can act as a stabilizing agent against crystalline transitions, which makes this approach interesting for a variety of applications.