Polymeric Network (polymeric + network)

Distribution by Scientific Domains


Selected Abstracts


Nanoscience for Art Conservation: Oil-in-Water Microemulsions Embedded in a Polymeric Network for the Cleaning of Works of Art,

ANGEWANDTE CHEMIE, Issue 47 2009
Emiliano Carretti Dr.
So gut wie neu: Öl-in-Wasser-Nanobehälter in einem wässrigen Polymernetzwerk ermöglichten ein effektives, weitgehend zerstörungsfreies und selektives Reinigen von bemalten und vergoldeten Oberflächen. Wechselwirkungen mit dem Polymer (im Bild schwarz) veränderten die Struktur der Mikroemulsions-Nanotröpfchen (hellblau und rot) kaum. Ein Foto einer Gleichgewichtsmischung aus Mikroemulsion und Polymer ist ebenfalls gezeigt. [source]


Syntheses, Crystal Structures and Magnetic Properties of Carboxylato-Bridged Polymeric Networks of MnII

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006
Subal Chandra Manna
Abstract Three new carboxylato-bridged polymeric networks of MnII having,molecular formula [Mn(ox)(dpyo)]n (1), {[Mn2(mal)2(bpee)(H2O)2]·0.5(bpee)·0.5(CH3OH)}n (2) and {[Mn3(btc)2(2,2,-bipy)2(H2O)6]·4H2O}n (3) [dpyo, 4,4,-bipyridine N,N,-dioxide; bpee, trans -1,2 bis(4-pyridyl)ethylene; 2,2,-bipy, 2,2,-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex 1 reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via - and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Metal-Directed Self-Assembly: Two New Metal-Binicotinate Grid Polymeric Networks and Their Fluorescence Emission Tuned by Ligand Configuration

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2004
Benlai Wu
Abstract Two new 2-D metal-binicotinate coordination polymers, namely, [CdII(bpdc)]n (1) and {[ZnII8(bpdc)8(H2O)8](H2O)8}n (2) (H2bpdc = binicotinic acid) have been synthesized using hydrothermal and three-layer diffusion methods, respectively. Single-crystal X-ray analyses revealed that both are extended grid networks of the (4,4) topology. Their structures alter with the configuration and function of bpdc. The achiral, free H2bpdc has axial chirality induced by metal coordination in 1, and bpdc connects to four metal centers forming a 2-D (4,4) net with three kinds of apertures generated through self-assembly. In 2, however, bpdc connects to three metal centers, fabricating a microporous framework containing hydrophilic channels. Studies on the solid emission spectra of the free ligand, 1, and 2 confirmed, that the configuration of bpdc resulting from metal-directed coordination has a profound effect on the fluorescence emissions of 1 and 2. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


Temperature-Sensitive Simultaneous Interpenetrating Polymeric Networks With Improved Mechanical Properties and Shrinking Kinetics,

ADVANCED ENGINEERING MATERIALS, Issue 3 2009
Jian-Tao Zhang
In this study, a new IPN structure was designed and a simultaneous method was for the first time utilized to prepare temperature sensitive PNIPAAm IPN hydrogels by carrying out the radical polymerization and hydrolysis/condensation for two kinds of reaction at the same time. Due to the specific structures, the newly prepared simultaneous IPN gels displayed higher elastic modulus and faster shrinking rates than the conventional PNIPAAm gel. [source]


Redox Active Two-Component Films of Palladium and Covalently Linked Zinc Porphyrin,Fullerene Dyad

ELECTROANALYSIS, Issue 9 2006
Marta Plonska
Abstract Redox active films have been generated electrochemically by the reduction of dyads consisting of fullerene C60 covalently linked to zinc meso -tetraphenyloporphyrin, ZnPC60, and palladium acetate. The films are believed to consist of a polymeric network formed via covalent bonds between the palladium atoms and the fullerene moieties. In these films, the zinc porphyrin moiety is covalently linked to the polymeric chains through the pyrrolidine ring of the fullerene. The ZnPC60/Pt films are electrochemically active in both positive and negative potential excursions. At positive potentials, two oxidation steps for the zinc porphyrin are observed. In the negative potential range, electron transfer processes involving the zinc porphyrin and the fullerene entities are observed. Film formation is also accompanied by palladium deposition on the electrode surface. The presence of a metallic phase in the film influences its morphology, structure and electrochemical properties. [source]


(Pyrazole)silver(I) and -gold(I) Complexes with Strong and Weak Hydrogen-Bonding Interactions as the Basis of One- or Two-Dimensional Structures

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2004
M. Luz Gallego
Abstract New AuI/AgI complexes containing one or two substituted pyrazole ligands [Au(Hpzbp2)(PPh3)](p -CH3C6H4SO3) [Hpzbp2 = 3,5-bis(4- n -butoxyphenyl)pyrazole] (1) and [M(HpzR2)2]nX [HpzR2 = Hpzbp2, M = Au, n = 1, X = p -CH3C6H4SO3 (2), NO3, (3); n = 2, X = 1,5-naphthalenedisulfonate (1,5nds) (4); HpzR2 = Hpzbp2, M = Ag, n = 1, X = BF4, (5), CF3SO3, (6); HpzR2 = HpzNO2 (3,5-dimethyl-4-nitropyrazole), M = Ag, n = 1, X = BF4, (7), CF3SO3, (8)], have been prepared and characterized. Compounds 1, 2, 5 and 8 have been proved to be useful for supramolecular assembly from their single X-ray diffraction analysis. In all cases strong hydrogen bonds maintain the cationic units bonded to their corresponding counterions. The crystal packing arrangement of 1, 2 and 5 is, however, determined by weak C,H···O/F hydrogen-bonding interactions involving the remaining O/F atoms of the counterion. By contrast, for 8 a two-dimensional layer-type polymeric network is formed by ,···, (NO2···NO2) and coordinative Ag···O interactions in which the NO2 substituent on the pyrazole is implicated. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]


The combination of a hydroxy-functional organophosphorus oligomer and melamine-formaldehyde as a flame retarding finishing system for cotton

FIRE AND MATERIALS, Issue 2 2005
Charles Q. Yang
Abstract In previous research, it was found that melamine-formaldehyde resin can be used as a binder for a hydroxy-functional organophosphorus flame retarding agent (FR) on cotton. The role that trimethylol melamine (TMM) plays in this flame retarding system was studied. When TMM is applied to cotton, it forms crosslinks between cellulose molecules. When TMM is applied to cotton in the presence of FR, it reacts with FR to form a crosslinked polymeric network in addition to reacting with cotton. The formation of the crosslinked network improves the laundering durability of FR and also increases the fabric stiffness. The number of crosslinks among cotton cellulose formed by TMM decreases as the FR concentration in the system is increased. TMM also functions as a nitrogen provider to enhance the flame retarding performance of FR due to phosphorus,nitrogen synergism. Therefore, the amount of TMM used in a FR/TMM formula plays the most critical role in determining the effectiveness of this flame retarding system. The finish bath pH also plays a significant role in influencing the performance of the flame retarding system on cotton. The optimum pH was found to be around 4. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Mimicking biological delivery through feedback-controlled drug release systems based on molecular imprinting

AICHE JOURNAL, Issue 6 2009
David R. Kryscio
Intelligent drug delivery systems (DDS) are able to rapidly detect a biological event and respond appropriately by releasing a therapeutic agent; thus, they are advantageous over their conventional counterparts. Molecular imprinting is a promising area that generates a polymeric network which can selectively recognize a desired analyte. This field has been studied for a variety of applications over a long period of time, but only recently has it been investigated for biomedical and pharmaceutical applications. Recent work in the area of molecularly imprinted polymers in drug delivery highlights the potential of these recognitive networks as environmentally responsive DDS that can ultimately lead to feedback controlled recognitive release systems. © 2009 American Institute of Chemical Engineers AIChE J, 2009. [source]


Characterization of ring-opening polymerization of genipin and pH-dependent cross-linking reactions between chitosan and genipin

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2005
Fwu-Long Mi
Abstract In this study, a novel chitosan-based polymeric network was synthesized by crosslinking with a naturally occurring crosslinking agent,genipin. The results showed that the crosslinking reactions were pH-dependent. Under basic conditions, genipin underwent a ring-opening polymerization prior to crosslinking with chitosan. The crosslink bridges consisted of polymerized genipin macromers or oligomers (7 , 88 monomer units). This ring-opening polymerization of genipin was initiated by extracting proton from the hydroxyl groups at C-1 of deoxyloganin aglycone, followed by opening the dihydropyran ring to conduct an aldol condensation. At neutral and acidic conditions, genipin reacted with primary amino groups on chitosan to form heterocyclic amines. The heterocyclic amines were further associated to form crosslinked networks with short chains of dimmer, trimer, and tetramer bridges. An accompanied reaction of nucleophilic substitution of the ester group on genipin by the primary amine group on chitosan would occur in the presence of an acid catalysis. The extent in which chitosan gels crosslinked with genipin was significantly dependent on the crosslinking pH values: 39.9 ± 3.8% at pH 5.0, 96.0 ± 1.9% at pH 7.4, 45.4 ± 1.8% at pH 9.0, and 1.4 ± 1.0% at pH 13.6 (n = 5, p < 0.05). Owing to the different crosslinking extents and different chain lengths of crosslink bridges, the genipin-crosslinked chitosan gels showed significant difference in their swelling capability and their resistance against enzymatic hydrolysis, depending on the pH conditions for crosslinking. These results indicated a direct relationship between the mode of crosslinking reaction, and the swelling and enzymatic hydrolysis properties of the genipin-crosslinked chitosan gels. The ring-opening polymerization of genipin and the pH-dependent crosslinking reactions may provide a novel way for the preparation and exploitation of chitosan-based gels for biomedical applications. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1985,2000, 2005 [source]


Multiphysics Modelling of Volume Phase Transition of Ionic Hydrogels Responsive to Thermal Stimulus

MACROMOLECULAR BIOSCIENCE, Issue 9 2005
Hua Li
Abstract Summary: This paper presents the analysis of the volume phase transition of ionic thermo-sensitive hydrogels to thermal stimulus through mathematical modelling. The model is termed the multi-effect-coupling thermal-stimulus (MECtherm) model and it considers the effects of multi-phases and multi-physics. Its application to steady-state analysis of the hydrogels in swelling equilibrium is validated against available experimental data for the relation between volume swelling ratio and temperature, in which very good agreement is achieved. The phenomenon of volume phase transition is studied for the thermal-stimulus responsive hydrogel. The numerical studies predict well the influences of initially fixed charge density and initial volume fraction of polymeric network on the swelling equilibrium of the hydrogels. Comparison of numerical simulations with the experimental swelling data for the thermo-sensitive PNIPA hydrogels in pure water. [source]


Thiol-ene Hybrid Organic/Inorganic Nanostructured Coatings Based on Thiol-Functionalized Zirconium Oxoclusters

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2007
Marco Sangermano
Abstract The thiol-functionalized zirconium oxocluster Zr12(µ3 -O)8(µ3 -OH)8(MP)24,·,4MPA was used as inorganic nanosized building block in the thiol-ene photopolymerization of APE and TH in a 1:1 molar mixture. Transparent and crack-free coatings were obtained, and TEM analysis showed that the inorganic particles are well dispersed within the polymeric network with no significant macroscopic agglomeration. An increase of Tg values, storage modulus in the rubbery region, and thermal stability were evidenced by increasing the zirconium oxocluster content in the photocurable formulations. XPS analysis and SIMS depth profile were carried out on UV cured films and showed the presence of a homogeneously distributed zirconium oxocluster. [source]


Study on superabsorbent composite.

POLYMER COMPOSITES, Issue 8 2009

In this work, the effects of different cation-exchanged montmorillonite on water absorbency of poly(acrylic acid- co -acrylamide)/montmorillonite/sodium humate (PAA-AM/MMT/SH) superabsorbent composite were systematically investigated under the same preparation conditions. The superabsorbents doped with different cation-exchanged montmorillonite were characterized by Fourier-transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy technologies. Swelling behaviors of developing superabsorbent composite in various cationic saline solutions (NaCl, CaCl2, and FeCl3) were also investigated. The water absorbencies of superabsorbent composite with 20 wt% MMT and 30 wt% SH are 638, 723, 682, and 363 g g,1 in distilled water for incorporating natural Na+ -MMT, Li+ -exchanged MMT, Ca2+ -exchanged MMT, and Al3+ -exchanged MMT, respectively. The results showed that the cation-exchange process had some obvious influences on final water absorbency of superabsorbent composite. NaCl, CaCl2, and FeCl3 solutions did not alter the swelling characteristics of the superabsorbent materials at a concentration of less than 0.01 mM, however, a concentration of greater than 0.1 mM caused a collapse in the swelling curves. The excellent swelling-reswelling-swelling behavior and lower swelling rate testified that Al3+ -exchanged MMT can act as an assistant crosslinker in the polymeric network. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source]


A fiber optic thermoset cure monitoring sensor

POLYMER COMPOSITES, Issue 4 2000
Michele Giordano
Curing determines the chemical and physical properties of a reacting resin. Among these, the optical properties strongly correlate with the structural features of the developing polymeric network. By monitoring changes of the refractive index, it is possible to analyze the polymerization of thermoset resin. In this work, a fiber optic sensor system has been designed and developed (based on the optical time domain reflectometry principle) to measure the reflection coefficient at the interface between the fiber optic and the resin during a curing process. Correlation between the sensor output and conversion has been proposed, following the Lorentz-Lorenz law. Isothermal data from the sensor have been compared with calorimetric analysis of an epoxy-based resin. [source]


Interpenetrating polymeric network hydrogels for potential gastrointestinal drug release

POLYMER INTERNATIONAL, Issue 11 2007
Sema Ekici
Abstract New interpenetrating polymeric network (IPN) hydrogels based on chitosan (C), poly(N -vinyl pyrrolidone) (PVP) and poly(acrylic acid) (PAAc), crosslinked with glutaraldehyde (G) and N,N,-methylenebisacrylamide (MBA), were prepared and investigated for potential gastrointestinal drug delivery vehicles utilizing a model drug, amoxicillin. IPN hydrogels were synthesized by simultaneous polymerization/crosslinking of acrylic acid monomer in the presence of another polymer (C) and crosslinker (G, MBA). Three different concentrations of glutaraldehyde were used (0.5, 1.0 and 2.0 w/w) to control the overall porosity of the hydrogels, named C-P-AAc/0.5, C-P-AAc/1.0 and C-P-AAc/2.0, respectively. Spectroscopic and thermal analyses such as Fourier transform infrared spectroscopy, thermogravimetric analysis and thermomechanical analysis were performed for IPN characterization. Equilibrium swelling studies were conducted for pH and temperature response behavior. Swelling studies were also carried out in simulated gastric fluid of pH = 1.1 and simulated intestinal fluid of pH = 7.4 to investigate possible site-specific drug delivery. It was found that the release behavior of the drug from these IPN hydrogels was dependent on the pH of the medium and the proportion of crosslinker in the IPN. It was observed that amoxicillin release at pH = 7.4 was higher than at pH = 1.1. The analysis of the drug release showed that amoxicillin was released from these hydrogels through a non-Fickian diffusion mechanism. Copyright © 2007 Society of Chemical Industry [source]


Polymeric gels and hydrogels for biomedical and pharmaceutical applications

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2010
Joseph Jagur-Grodzinski
Abstract Hydrogels are formed when a three-dimensional polymeric network is loosely crosslinked. They are swollen by water but not dissolved in it. Hydrogels may display reversible sol,gel transitions, induced by changes in the environmental conditions such as temperature, pH, ionic strength, phase separation, wave length of light, crystallinity, etc. Hydrogel is described as smart or intelligent when sharp transition is induced by small change in such conditions. For the shape-memory hydrogels, reversible change in shape may also be induced by such stimuli. The preparation and applications of the molecularly imprinted polymeric hydrogels (MIPs) are illustrated by a few examples. The use of shape sensitive hydrogels in microfluidic is mentioned. Application of hydrogels for chronobiology and chronotherapy is outlined. The conversion of hydrogels into aerogels and their respective properties is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Radiation synthesis of poly(N -vinyl-2-pyrrolidone-g-tartaric acid) hydrogels ­and their swelling behaviors

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 2 2002
Cengiz Özyürek
Abstract Poly(N-Vinyl 2-pyrrolidone-g-tartaric acid), PVP-g-TA hydrogels were prepared by ,-irradiating ternary mixture of VP/TA/Water. The influence of pH, temperature and ionic strength of swelling media on the equilibrium swelling properties of these hydrogels was investigated. Typical pH and temperature responses were observed by hydrogels such as high pH and low temperature swelling and low pH and high temperature deswelling. A change in the ionic strength of the swelling solution from 0.01 to 0.2 caused a decrease in equilibrium degree of swelling hydrogels. The average molecular weight between cross-links, Mc and polymer - solvent interaction parameter, , of PVP-g-TA hydrogels were determined according to equation recently derived by ,en and Güven for the swelling behavior of charged polymeric network. Copyright © 2002 John Wiley & Sons, Ltd. [source]


Syntheses, Crystal Structures and Magnetic Properties of Carboxylato-Bridged Polymeric Networks of MnII

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006
Subal Chandra Manna
Abstract Three new carboxylato-bridged polymeric networks of MnII having,molecular formula [Mn(ox)(dpyo)]n (1), {[Mn2(mal)2(bpee)(H2O)2]·0.5(bpee)·0.5(CH3OH)}n (2) and {[Mn3(btc)2(2,2,-bipy)2(H2O)6]·4H2O}n (3) [dpyo, 4,4,-bipyridine N,N,-dioxide; bpee, trans -1,2 bis(4-pyridyl)ethylene; 2,2,-bipy, 2,2,-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex 1 reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via - and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]


Synthesis of high fluorescent silica hybrid materials by immobilization of orange peel extract in silica-silsesquioxane matrix

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2009
I. Lacatusu
Abstract Sol,gel chemistry can be easily modified to the changing needs of society to produce fine-tuned sol,gel nanostructured materials for relevant applications. In this context, there is an increasing need for natural and versatile raw materials as well as biocompatible compounds that could be extensively used as biomarkers for bioimaging in diagnosis or therapy. Silica-based materials are widely used in the field of biomedicine due to their chemical inertness and biocompatibility. In the present paper, orange peel extract was immobilized inside inorganic silica and hybrid silica-silsesquioxane polymeric networks. Silica and organo-modified silica matrices were synthesized through a templated sol,gel route of TEOS and an organosilsesquioxane (octaisobutyltetracyclo[7.3.3.15,11] octasiloxane- endo -3,7-diol), with D -glucose as template, and for comparison a non-ionic surfactant (tetraethylene glycol mono-hexadecyl ether) was also used. The bioactive properties of the molecules from orange peel extract were preserved after immobilization in both silica and silica-silsesquioxane networks. Moreover, the fluorescence properties were amplified by 10,20 times more than the native orange peel extract. The structural properties of the final materials have been studied by FT-IR, UV,Vis-NIR, and fluorescence spectroscopy. Dynamic light scattering measurements and transmission electron microscopy were used to estimate the size and morphology of the hybrid materials with orange peel extract immobilized in silica networks. Copyright © 2009 John Wiley & Sons, Ltd. [source]


Synthesis and Characterization of Supramolecular Polymeric Materials Containing Azopyridine Units

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2006
Marta Millaruelo
Abstract Summary: The synthesis and characterization of a series of supramolecular polymeric complexes formed by H-bonding interactions between benzoic acid and azopyridine derivatives are described. A series of polymeric networks have been synthesized using a polymethacrylate bearing benzoic acid units as side groups, and several polymers with azopyridine as H-acceptor side groups. Furthermore, low-molecular-weight pyridine derivatives have been used to prepare an homologous side-chain polymer, and a network with azopyridine as a non-covalent crosslinker. Special attention was paid to the thermal and mesomorphic properties of these materials, which were studied by DSC, POM, and XRD. Micrograph of the mesomorphic melt of a sample taken at 130,°C on cooling from the isotropic state. [source]