Electrospinning of antibacterial poly(vinylidene fluoride) nanofibers containing silver nanoparticles

Poly(vinylidene fluoride) (PVDF) nanofibrous mats containing silver nanoparticles were prepared by electrospinning. The diameter of the nanofibers ranged between 100 and 300 nm, as revealed by scanning electron microscopy. The silver nanoparticles were dispersed, but some aggregation was observed with transmission electron microscopy. The content of silver nanoparticles incorporated into the PVDF nanofibrous mats was determined by inductively coupled plasma and X‐ray photoelectron spectroscopy. The antibacterial activities of the samples were evaluated with the colony‐counting method against Staphylococcus aureus (Gram‐positive) and Klebsiella pneumoniae (Gram‐negative) bacteria. The results indicate that the PVDF nanofibrous mats containing silver nanoparticles showed good antibacterial activity compared to the PVDF nanofiber control. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Performance assessment of poly (methacrylic acid)/silver nanoparticles composite as corrosion inhibitor for aluminium in acidic environment

This article reports the preparation of poly (methacrylic acid)/silver nanoparticles composite (PMAA/AgNPs) by in situ mixing of aqueous solutions of PMAA and 1 mM AgNO₃ with natural honey as reducing and stabilizing agent. The prepared PMAA/AgNPs composite was characterized by UV–vis spectroscopy, Fourier transformed infrared, X-ray diffraction and energy dispersive spectroscopy (EDS) while the morphology of the AgNPs in the composite was obtained by transmission electron microscopy (TEM). TEM results revealed that the AgNPs were spherical in shape. The performance of PMAA/AgNPs composite as anticorrosion material for Al in acidic environment was examined by electrochemical, weight loss methods, complemented by surface analysis characterization with scanning electron microscopy (SEM), EDS and water contact angle measurements. Results obtained indicate that PMAA/AgNPs composite is effective corrosion inhibitor for Al in an acid-induced corrosive environment. Inhibition efficiency increased with increase in composite concentration but decreased with rise in temperature. From potentiodynamic polarization results, PMAA/AgNPs composite is found to function as a mixed-type corrosion inhibitor. The adsorption of the composite onto Al surface was found to follow El-Awady et al. adsorption isotherm model. SEM, EDS and water contact angle results confirmed the adsorption of the composite on Al surface.     

聚甲基丙烯酸-苯乙烯-甲基丙烯酸的合成

以萘钠为引发剂双向引发活性阴离子聚合制备嵌段共聚物聚甲基丙烯酸叔丁酯-苯乙烯-甲基丙烯酸叔丁酯(PTBMA—PS—PTBMA)，并在碱性条件下水解合成了ABA型两亲嵌段共聚物聚甲基丙烯酸-苯乙烯-甲基丙烯酸(PMAA—PS—PMAA)。对产物进行了傅立叶红外光谱分析，热分析及凝胶色谱分析。当苯乙烯与α-甲基丙烯酸叔丁酯投料质量比为54：46时，所得共聚物相应嵌段质量比为79：2l左右。     

Structure formation in solutions of isotactic poly(methacrylic acid) in dimethyl formamide

Summary Structure formation in solutions of non-neutralised isotactic poly(methacrylic acid) in dimethyl formamide was studied. Fourier transformed infrared spectroscopic measurements, X-ray diffraction analysis and dynamic rheological observations revealed that two different processes of structure formation can take place. The first process can lead to the formation of very weak, thermoreversible gels. It is proposed to consist of an intramolecular coil-to-helix transition, followed by an intermolecular association. The second one shows the characteristics of a crystallisation into a supramolecular organisation different from what is obtained in the first process. These processes can compete with each other and this depends on the experimental conditions, the molar mass and the tacticity of the sample.     

NMR of the formation of cyclic imide on poly(methacrylic acid)

Summary The reaction of syndiotactic poly (methacrylic acid) and formamide above 100C yields a syndiotactic copolymer of methacrylic acid and dimethacryloylimide. The ₁₃C-NMR spectra of the copolymers show resolved -CH₃ and C=O resonances which are evaluated to yield the triad probabilities. The triad statistics prove a nearly random formation of the cyclic imide along the polymer chain.     

Poly(acrylic acid) hydrogel microparticles fabricated with silver nanoparticles: synthesis,characterization, and catalytic applications

This work narrates the synthesis of poly (acrylic acid) hydrogel microparticles (PAAHMPs), fabrication of silver nanoparticles (AgNPs) inside the structure of the prepared PAAHMPs and catalytic applications of PAAHMPs fabricated with AgNPs (PAAHMPs/AgNPs). The PAAHMPs were prepared by inverse suspension polymerization technique while fabrication of AgNPs was carried out by chemical reduction method using sodium borohydride (NaBH₄) as reducing agent. The identification of functional groups in bare PAAHMPs and in the PAAHMPs/AgNPs composite system was carried out by the Fourier transform infrared spectroscopy. The size and morphology of the prepared hydrogel and its composite was studied by scanning electron microscopy and transmission electron microscopy. X-ray diffraction and thermal gravimetric analyzer was also used to characterize the bare PAAHMPs and PAAHMPs/AgNPs composite. The prepared PAAHMPs/AgNPs composite was used as catalyst for the reduction of nitro aromatic pollutants and an industrial dye, that is, 4-Nitrophenol (4-NP), 2-Nitrophenol (2-NP) and methyl orange. No loss in catalytic activity was noted in seven consecutive cycles of recycling process while only 37.5% loss in catalytic activity was observed upon storing the catalyst for 90 days.     

Complexation between poly(methacrylic acid) and poly(vinylpyrrolidone)

The complexation between poly(methacrylic acid) (PMAA) and poly(vinylpyrrolidone) (PVP) in aqueous phase was studied by various fluorescence techniques, including fluorescence anisotropy measurements, fluorescence probe studies, and nonradiation energy transfer. It was demonstrated that the complexation of PMAA with PVP occurs within a pH range of 1 to 5 and along with complexation, the conformation of PMAA changed from a hypercoiled to a loosely coiled form. The complex ratio between the two polymers is 2:1 (PMAA/PVP, in monomer unit). Salt effect studies showed that the complexation occurred due to formation of hydrogen bonds between the two polymers. Based on these conclusions and the “connected cluster model” for PMAA at low pH, a “ladder with connected cluster” model was proposed for the structure of PMAA/PVP complex formed at low pH. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 620–627, 2001     

Complex formation in the template polymerization of methacrylic acid along poly(2-vinylpyridine)

Summary The polymerization of methacrylic acid in presence of poly/2-vinylpyridine/ of different molecular weight was investigated. The resulted complex has been separated and analysed by elemental analysis and UV spectrometry. The kinetics of complex formation was examined by means of nephelometric analysis and determination of acid groups. The results obtained show that the complex formation rate does not depend visibly on the degree of polymerization of the template due to the template polymerization.     

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Preparation and catalytic properties of composites with palladium nanoparticles and poly(methacrylic acid) microspheres

Palladium (Pd) nanoparticles with different sizes are in situ synthesized by reduction of PdCl₂ with NaBH₄ as reductant in the presence of poly(methacrylic acid) (PMAA)microspheres. The obtained PMAA/Pd composites are characterized by Fourier transform infrared spectra, X‐ray diffraction, and Transmission electron microscopy. The catalytic activity of the PMAA/Pd composites is investigated using a model reaction, that is, reduction of p‐nitrophenol to p‐aminophenol. The reaction shows first‐order kinetics, and the reaction rate increases with increasing reaction temperature, p‐nitrophenol concentration, and loadings of Pd nanoparticles on PMAA microspheres. The PMAA/Pd composites exhibit good stability, ascribing to the Pd nanoparticles stabilized by PMAA microspheres. POLYM. COMPOS., 35:2251–2260, 2014. © 2014 Society of Plastics Engineers     

Dispersion of nanoparticles in poly(vinyl chloride) grains during In situ polymerization

Inorganic nanoparticles such as calcium carbonate, silica, or hydrotalcite were dispersed in vinyl chloride prior to suspension polymerization. That led to the production of poly(vinyl chloride) (PVC) composite grains with higher porosity and different internal morphology from those of commercial PVC. The PVC/composite grain sizes and their distribution were also influenced by the presence of nanofillers. The distribution of filler nanoparticles (either calcium carbonate or silica) was not uniform throughout the PVC grains. Regions of high and low filler concentration were observed. Regions of pure polymer were also observed. Reasons for that are suggested. Hydrotalcite did not remain in the PVC grains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

In situ immobilization of alkaline protease during inverse suspension polymerization of polyacrylamide and poly(acrylamide-co-methacrylic acid) hydrogel beads

We report the in situ immobilization of alkaline protease in highly porous polyacrylamide and poly(acrylamide-co-methacrylic acid) hydrogel beads synthesized by inverse suspension polymerization using ammonium persulfate, N,N,N′,N′,-tetraethylmethylenediamine as the redox initiator. The influences of reaction variables on the polymerization, conversion, enzymatic activity, water absorption, and LCST properties were studied in detail. Evaluation of the enzymatic activities on various substrates was carried out for potential applications in the detergent industry. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2273–2291, 1999     

Solubility parameters of polymethacrylonitrile,poly(methacrylic acid) and methacrylonitrile/methacrylic acid copolymer

The solubility behaviors of polymethyacrylonitrile (PMAN), poly(methacrylic acid) (PMAA), and its random copolymer methacrylonitrile (MAN)/methacrylic acid (MAA) in various solvents were investigated. The results were used in a computer program to obtain a 3-dimensional representation of the polymer solubility region in the Hansen space. Thus, the values of dispersion (δ_d,p), polar (δ_p,p) and hydrogen bonding (δ_h,p) components of the total solubility parameter (δ_t,p) were obtained. Comparisons between the experimental results and the estimated values are discussed. Also, prediction for solubility parameter values for MAN/MAA copolymer via their homopolymers, PMAN, and PMAA has been evaluated.     

Complex system of poly(methacrylic acid) with poly(vinylpyrrolidone) in aqueous media

Two‐component polymer solutions [i.e., poly(methacrylic acid) (PMAA) and poly(vinylpyrrolidone) (PVP)] were prepared through solution polymerization. The complex system PMAA/PVP was obtained through the mixing of a PMAA solution and a PVP solution in different volume ratios at certain concentrations. The properties of the component solutions and the complex system were investigated with transmittance, surface tension, and viscosity measurements. The results showed that the properties of the complex system were related not only to the ratio of PMAA to PVP but also to the concentration of the PMAA and PVP solutions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2280–2286, 2005     

A sweet killer: mesoporous polysaccharide confined silver nanoparticles for antibacterial applications

Silver nanoparticles (AgNP) confined within porous starch have been prepared in a simple, green and efficient manner, utilising the nanoporous structure of predominantly mesoporous starch (MS) to act as nanoparticle stabiliser, support and reducing surface. MS/AgNP materials present high surface areas (S(BET) > 150 m(2) g(-1)) and mesopore volumes (V(meso) > 0.45 cm(3) g(-1)). The interaction of the AgNP precursor and forming nanoparticle nuclei with the mesoporous domains of the porous polysaccharide, direct porosity to increasingly narrower and more defined pore size distributions, indicative of a degree of cooperative assembly. Transmission electron microscopy images indicated the presence of spherical AgNP of a size reflective of the porous polysaccharide mesopore diameter (e.g., 5-25 nm), whilst XPS analysis confirmed the metallic Ag(0) state. Materials were prepared at relatively low Ag loadings (<0.18 mmol g(-1)), demonstrating excellent antimicrobial activity in solid and liquid phase testing against Gram negative (E. coli) and positive (S. aureus) model bacteria. The resulting materials are biocompatible and present a useful solid porous carbohydrate-based polymer vehicle to control the AgNP size regime and facilitate transference to a biological environment.     

Formation of polyvinylpyrrolidone-syndiotactic poly(methacrylic acid) complexes in dimethylformamide

Interpolymer complex formation between polyvinylpyrrolidone and syndiotactic poly(methacrylic acid) has been studied using dimethylformamide as solvent. Compact and globular complex particles are formed, with equimolar composition. The increase of compactness of the particles on raising the temperature as well as the volume expansion on mixing solutions of component polymers indicate that the complexation is predominantly determined by desolvation. In this connection, it may be assumed that besides the cooperative hydrogen bonding force between the polymers some kind of ‘solvophobic interaction’ between segments of the polymer complex determines the ultimate structure of the complex.     

Growth of silver nanoparticles on poly(acrylic acid) brushes and their properties

A simple procedure is employed for the growth of silver nanoparticles (Ag NPs) onto the silicon substrate modified by poly(acrylic acid) (PAA) brushes, via: (1) surface-initiated ATRP of tert-butyl acrylate on Si surface to the preparation of poly(tert-butyl acrylate) brushes, (2) acid hydrolysis of PBA to the formation of PAA, and (3) in situ synthesis of Ag NPs via chemical reduction of AgNO₃ in the presence of PAA brushes. The polymer brushes are thoroughly characterized. Moreover, Ag nanoparticles are homogeneously immobilized into the brush layer and have been used to fabricate a sensor platform of surface-enhance Raman scattering for the detection of organic molecules and effectively catalyze the reduction of methylene blue by NaBH₄.     

In situ chlorination of poly(vinyl chloride) in aqueous hydrochloric acid

Based on environmental, safety, corrosion and technological considerations a new method has been developed for chlorination of PVC in aqueous hydrochloric acid solvent by controlled electrolytic in situ generation of chlorine using graphite and chlorine-selective Ti-RuO₂ electrodes. The byproduct, HCl gas, is dissolved at the moment of its formation and acts as starting material of further chlorination. This way, the application of corrosive chlorine gas is avoided. The chlorination conditions have been optimized. The highest chlorine content was found at 5.5 h reaction time using a graphite electrode. The obtained chlorinated PVC did not contain any CCl₂ units.     

Stereoselective association between isotactic poly(methylmethacrylate) and syndiotactic poly(methacrylic acid)

An extensive viscometric investigation has been carried out into the stereo-association between isotactic poly(methyl methacrylate) (it-PMMA) and syndiotactic poly(methacrylic acid) (st-PMAA) in different solvents and solvent mixtures. Solvent media were classified into three types, A, B and C, depending on their decreasing ability to promote complex formation. In all ‘complexing’ solvents (type A and B), even in the best one consisting of a mixture of 83 vol % ethanol and 17 vol % water, only one of the four possible cross-combinations of tactic PMMA and PMAA can associate. This stereoselectivity was confirmed by a calorimetric (d.s.c.) study of the glass transition of the various mixtures in the bulk. The it-PMMA/st-PMAA complex, although it is weaker, resembles the well known it/st-PMMA stereocomplex in many respects. It is suggested that association occurs primarily due to stereo-complementarity of the components involving interaction of the ester groups of it-PMMA with the α-methyl groups of st-PMAA and not to hydrogen bonding via the carboxyl groups of st-PMAA.