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Polymer Networks (polymer + network)
Kinds of Polymer Networks Terms modified by Polymer Networks Selected AbstractsSynthesis of Microporous Carbon Nanofibers and Nanotubes from Conjugated Polymer Network and Evaluation in Electrochemical CapacitorADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Xinliang Feng Abstract One-dimensional fibers and tubes are constructed through the oriented carbon-carbon cross-linking reactions towards rigid conjugated polymer networks. As the result, a template-free and one-step synthesis of CNTs and CNFs is achieved through a simple carbonization of the as-formed carbon-rich tubular and fiberlike polyphenylene precursors under argon. Microporous CNTs and CNFs with a surface area up to 900 m2 g,1 are obtained, together with HR-TEM characterizations indicating the formation of intrinsic microporous structure in these rigid carbon-rich networks. The primary electrochemical experiments reveal their promising applications as advanced electrodes in electrochemical double-layered capacitor (EDLC). [source] Solid-State NMR Investigations of the Unusual Effects Resulting from the Nanoconfinement of Water within Amphiphilic Crosslinked Polymer NetworksADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Ryutaro Ohashi Abstract Two types of solid-state 19F NMR spectroscopy experiments are used to characterize phase-separated hyperbranched fluoropolymer,poly(ethylene glycol) (HBFP,PEG) crosslinked networks. Mobile (soft) domains are detected in the HBFP phase by a rotor-synchronized Hahn echo under magic-angle spinning conditions, and rigid (hard) domains by a solid echo with no magic-angle spinning. The mobility of chains is detected in the PEG phase by 1H,,,13C cross-polarization transfers with 1H spin-lock filters with and without magic-angle spinning. The interface between HBFP and PEG phases is detected by a third experiment, which utilized a 19F,,,1H,(spin diffusion),1H,,,13C double transfer with 13C solid-echo detection. The results of these experiments show that composition-dependent PEG inclusions in the HBFP glass rigidify on hydration, consistent with an increase in macroscopic tensile strength. [source] One-Step Process for Creating Triple-Shape Capability of AB Polymer NetworksADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Marc Behl Abstract Triple-shape polymers can move from a first shape (A) to a second shape (B) and from there to a third shape (C), where both shape changes are induced by temperature increases. This triple-shape capability is obtained for multiphase polymer networks after application of a complex thermomechanical programming process, which consists of two steps; these steps create shapes (B) and (A), while shape (C) is defined by the covalent crosslinks of the polymer network. Here, the creation of the triple-shape capability for an AB polymer network system by a simple one-step process similar to a conventional dual-shape programming process is reported. The polymer networks are based on poly(, -caprolactone) (PCL) and poly(cyclohexyl methacrylate); favorable compositions for obtaining a triple shape effect have a PCL content between 35 and 60 wt%. This finding substantially facilitates handling of the triple-shape technology and is an important step toward the realization of potential applications in which more than one shape change is required. [source] One- and Two-Dimensionally Structured Polymer Networks in Liquid Crystals for Switchable Diffractive Optical Applications,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2004P. Kossyrev Abstract We have created one- and two-dimensionally structured polymer networks dispersed in a liquid-crystal solvent using a holographic exposure technique. These structures have potential for electrically switchable, reverse-mode, polarization selective and non-selective diffractive optical elements. Using a simple phenomenological model to describe our diffraction measurements in conjunction with microscopic studies, we are able to estimate the structured polymer wall thickness as a function of monomer concentration. [source] Tailored (Meth)Acrylate Shape-Memory Polymer Networks for Ophthalmic ApplicationsMACROMOLECULAR BIOSCIENCE, Issue 10 2010Li Song Abstract The unique features of shape-memory polymers enables their use in minimally invasive surgical procedures with a compact starting material switching over to a voluminous structure in vivo. In this work, a series of transparent, thermoset (meth)acrylate shape-memory polymer networks with tailored thermomechanics have been synthesized and evaluated. Fundamental trends were established for the effect of the crosslinker content and crosslinker molecular weight on glass transition temperature, rubbery modulus and shape-recovery behavior, and the results are intended to help with future shape-memory device design. The prepared (meth)acrylate networks with high transparency and favorable biocompatibility are presented as a promising shape-memory ophthalmic biomaterial. [source] Interpenetrating Polymer Networks of Hydrocarbon and Fluorocarbon Polymers: Epoxy/Fluorinated Acrylic MacromonomersMACROMOLECULAR MATERIALS & ENGINEERING, Issue 5 2010Marco Sangermano Abstract A fluorinated acrylic resin was synthesized for use as a co-monomer with a commercially available epoxy resin for UV-cured interpenetrating polymer network preparation. Hybrid IPN networks were achieved with morphology ranging from a co-continuous IPN to complete phase separation simply by changing monomer ratios. Highly hydrophobic coatings with good adhesion properties on glass substrates were obtained. [source] Interpenetrating Polymer Networks with Spatially Graded Morphology Controllable by UV-Radiation CuringMACROMOLECULAR SYMPOSIA, Issue 1 2006Hideyuki Nakanishi Abstract Interpenetrating Polymer Networks (IPNs) composed of polystyrene (PS) and poly(methyl methacrylate) (PMMA) were synthesized from a precursor mixture by using dissimilar photo-cross-link reactions. When the reation yields exceeded a certain threshold, the mixture was quenched from one-phase region into two-phase region, leading to phase separation. Upon irradiation with strong UV-light, an intensity gradient was formed along the propagating direction of the exciting light, generating a gradient of quench depth via the spatial inhomogeneity of the cross-link reactions. As a consequence, a gradient of the characteristic length scales was continuously generated from the top to the bottom of the mixture. The resulting three-dimensional (3-D) morphology was in-situ observed at different depths of the mixture by using a laser-scanning confocal microscope (LSCM). From this 3-D observation, it was found that phase separation was accelerated at the bottom of the mixture and proceeded in an autocatalytic fashion. The mechanism for the formation of the graded morphology was discussed in conjunction with the kinetics of the autocatalytic phase separation. [source] Highly Selective CO2 Capture in Flexible 3D Coordination Polymer Networks,ANGEWANDTE CHEMIE, Issue 37 2009Hye-Sun Choi Bleib flexibel: 3D-Koordinationspolymere mit flexiblen Säulen (links im Bild) adsorbieren CO2 hoch selektiv gegenüber N2, H2 und CH4 (rechts im Bild), sind bis 300,°C thermisch stabil sowie luft- und wasserbeständig und ermöglichen eine effiziente CO2 -Bindung, -Speicherung und -Identifizierung. [source] Segmented polymer networks containing amino-dendrimersPOLYMER INTERNATIONAL, Issue 2 2003Leen M Tanghe Abstract Polymer networks in which poly(propylene imine) dendrimers (AstramolÔ) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one-step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino-dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two-step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino-dendrimer, to form a star-like, acrylate-terminated polyTHF multi-macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end-groups and unreacted amino-groups of the dendrimer. This cross-linking reaction occurred spontaneously upon heating of the solution of the multi-macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry [source] Light-induced crosslinking polymerization,POLYMER INTERNATIONAL, Issue 11 2002Christian Decker Abstract Light-induced polymerization of multifunctional monomers is a powerful method to transform a liquid resin into a solid polymer almost instantly, selectively in the illuminated areas. The reaction can conveniently be followed by real-time infrared spectroscopy, a technique which records directly conversion versus time curves in photosensitive resins undergoing ultrafast curing upon UV or laser exposure. The photoinitiator was shown to play a key role in laser-induced polymerization because of the monochromatic character of the emitted radiation. By using highly sensitive acrylate photoresists, relief images of micronic size were obtained by fast scanning with a focused laser beam. The laser direct imaging technology makes image transfer obsolete and eliminates the manufacture of photolithographic masks. Polymer networks of different architectures have been obtained by UV irradiation of various monomer blends: acrylate,epoxide, acrylate,vinyl ether, acrylate,polyene, vinyl ether,maleate and thiol,polyene. With monomers polymerizing by different mechanisms, ie radical and cationic types, interpenetrating polymer networks have been generated upon UV exposure in the presence of adequate photoinitiators. The crosslinking reaction was also performed in the solid state on polybutadiene which was plasticized with a multifunctional acrylate or thiol monomer. Thermoplastic elastomers were transformed within a fraction of a second into an insoluble material showing a greatly improved resistance to heat and chemicals, because of the tight polymer network formed. © 2002 Society of Chemical Industry [source] Proteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Daniel Dikovsky Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source] Oxygen-Generating Gel Systems Induced by Visible LightADVANCED FUNCTIONAL MATERIALS, Issue 5 2010Kosuke Okeyoshi Abstract Toward complete artificial photosynthesis systems to generate hydrogen and oxygen using visible light and water, oxygen-generating gel systems are designed and fabricated using the electrostatic interactions of ionic functional groups and steric effects of a polymer network. By using a graft polymer chain with Ru(bpy)32+ units as sensitizers to closely arrange RuO2 nanoparticles as catalyst, the functional groups transmit multiple electrons cooperatively to generate oxygen. In this paper, a novel strategy is shown to design a hierarchical network structure using colloidal nanoparticles and macromonomers. Such a soft material to oxidize water inside a hydrogel is useful as a solar-energy converting system. [source] One-Step Process for Creating Triple-Shape Capability of AB Polymer NetworksADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Marc Behl Abstract Triple-shape polymers can move from a first shape (A) to a second shape (B) and from there to a third shape (C), where both shape changes are induced by temperature increases. This triple-shape capability is obtained for multiphase polymer networks after application of a complex thermomechanical programming process, which consists of two steps; these steps create shapes (B) and (A), while shape (C) is defined by the covalent crosslinks of the polymer network. Here, the creation of the triple-shape capability for an AB polymer network system by a simple one-step process similar to a conventional dual-shape programming process is reported. The polymer networks are based on poly(, -caprolactone) (PCL) and poly(cyclohexyl methacrylate); favorable compositions for obtaining a triple shape effect have a PCL content between 35 and 60 wt%. This finding substantially facilitates handling of the triple-shape technology and is an important step toward the realization of potential applications in which more than one shape change is required. [source] Poly(vinyl alcohol),polyacrylamide blends with cesium salts of heteropolyacid as a polymer electrolyte for direct methanol fuel cell applicationsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010M. Helen Abstract A class of inorganic,organic hybrid membranes with low methanol permeability characteristics for possible direct methanol fuel cell (DMFC) applications was architected, formulated, and fabricated through the blending of poly(vinyl alcohol) (PVA) and polyacrylamide (PAM) followed by crosslinking with glutaraldehyde (Glu). Cesium salts of different heteropolyacids, including phosphomolybdic acid (PMA), phosphotungstic acid (PWA), and silicotungstic acid (SWA), were incorporated into the polymer network to form corresponding hybrid membrane materials, namely, PVA,PAM,CsPMA,Glu, PVA,PAM,CsPWA,Glu, and PVA,PAM,CsSWA,Glu, respectively (where "Cs" together with a heteropolyacid abbreviation indicates the cesium salt of that acid). All the three hybrid polymer membranes fabricated exhibited excellent swelling, thermal, oxidative, and additive stability properties with desired proton conductivities in the range 10,2 S/cm at 50% relative humidity. A dense network formation was achieved through the blending of PVA and PAM and by crosslinking with Glu, which led to an order of magnitude decrease in the methanol permeability compared to the state-of-the-art commercial Nafion 115 membrane. The hybrid membrane containing CsSWA exhibited a very low methanol permeability (1.4 × 10,8 cm2/s) compared to other membranes containing cesium salt of heteropolyacids such as PMA and PWA. The feasibility of these hybrid membranes as proton-conducting electrolytes in DMFC was investigated, and the preliminary results were compared with those of Nafion 115. The results illustrate the attractive features and suitability of the fabricated hybrid membranes as an electrolyte for DMFC applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] A simple method to obtain a swollen PVA gel crosslinked by hydrogen bondsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Emiko Otsuka Abstract A simple method to obtain a physically crosslinked poly(vinyl alcohol) (PVA) hydrogel is reported. In this technique, the PVA solution in pure water was simply cast at room temperature without using any additional chemical. The gelation proceeded during the dehydration after casting the PVA solution into a mold. After the completion of gelation, the swelling ratio of the gel in its equilibrium was measured whenever the solvent water was repeatedly exchanged. The weight gradually decreased due to the elution of non-crosslinked polymers into the solvent, and became constant after sufficient water exchange. The measurements using a Fourier Transform infrared spectroscopy and an X-ray diffraction suggested that the crosslinks due to hydrogen bonds and microcrystals were formed during the dehydration process of the PVA solution. We concluded that the sample obtained by the present method is a physically crosslinked polymer network, insoluble in water, i.e., a swollen gel in water. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Preparation and characterization of interpenetration polymer network films based on poly(vinyl alcohol) and poly(acrylic acid) for drug deliveryJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yu-Mei Yue Abstract A series of full interpenetrating polymer network (full-IPN) films of poly(acrylic acid) (PAA)/poly (vinyl alcohol) (PVA) were prepared by radical solution polymerization and sequential IPN technology. Attenuated total reflectance-Fourier transform infrared spectroscopy, swelling properties, mechanical properties, morphology, and glass transition temperature of the films were investigated. FTIR spectra analysis showed that new interaction hydrogen bonds between PVA and PAA were formed. Swelling property of the films in distilled water and different pH buffer solution was studied. Swelling ratio increased with increasing PAA content of IPN films in all media, and swelling ratio decreased with increasing PVA crosslink degree. Tensile strength and elongation at break related not only to the constitution of IPNs but also to the swelling ratio of IPNs. Mechanical property of glutaraldehyde (0.5%) for poly(vinyl alcohol) crosslinking was better than that of glutaraldehyde (1.0%). DSC of the IPN films showed only a single glass transition temperature (Tg) for each sample, and Tg data showed a linear relationship with network composition. Morphology was observed a homogeneous structure, indicating the good compatibility and miscibility between PAA and PVA. Potential application of the IPN films in controlled drug delivery was also examined using crystal violet as a model drug. The release rate of the drug was higher at 37°C than 25°C for all IPNs and also increased slightly with decreasing of poly(acrylic acid) content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Tobramycin and Gentamycin elution analysis between two in situ polymerizable orthopedic compositesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2003M. DiCicco Abstract This research analyzed Tobramycin and Gentamycin elution characteristics for two antibiotic-impregnated bone composites: PMMA-based Simplex P® and the novel, hybrid, bioactive, CORTOSSÔ. Experimental results were correlated with composite hydrophilicity and antibiotic phase partitioning behaviors. The phase partitioning experiment was conducted to understand antibiotic solubility in aqueous environments. By comparing experimental results with calculated data, antibiotic release behavior was predicted. Total Tobramycin elution percentages from CORTOSS and Simplex P were 12.5 and 6.4%, respectively. Total Gentamycin elution percentages from CORTOSS and Simplex P were 6.95 and 10.17%, respectively. Phase partitioning data indicate 100% of Tobramycin remains in aqueous phases, being extremely hydrophilic. This is supported by its calculated theoretical value (log P = , 7.32). Results suggest that Tobramycin elution can be attributed to composite hydrophilicity as well as its high degree of hydrophilicity. Fifteen percent of Gentamycin distributes in hydrophobic phases (log P = , 4.22). Despite a lower Gentamycin hydrophilicity, its release was affected by its complexation with polar salts in the leaching buffer, thereby increasing its elution potential, making it appreciably water soluble. CORTOSS is more hydrophilic; therefore the migration of aqueous liquids into the polymer network of CORTOSS facilitates greater antibiotic elution compared with hydrophobic Simplex P. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 65B: 137,149, 2003 [source] Synthesis and characterization of stereoregular poly(methyl methacrylate),silica hybrid utilizing stereocomplex formationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2004Achimuthu Ashok Kumar Abstract Stereoregular poly(methyl methacrylate) (PMMA),silica nanocomposites were prepared using stereocomplex formation between i -PMMA and s -PMMA by an in situ method. The methodology adopted here is the simultaneous formation of organic gel and inorganic gel, the so-called interpenetrating polymer network (IPN) formation. The gelation of i - and s -PMMA were performed by stereocomplex formation with the associated segments forming the crosslinking points in the presence of tetramethoxysilane (TMOS). The effects of the i/s -ratio, PMMA concentration, molecular weight, and solvent nature on the hybrid materials formation were addressed. The presence of the stereocomplex in the silica matrix was confirmed by DSC and solvent extraction methods. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 785,794, 2004 [source] Crosslinking polymerization leading to interpenetrating polymer network formation.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2003Abstract As part of our continuing studies concerned with the elucidation of the crosslinking polymerization mechanism leading to interpenetrating polymer network (IPN) formation, in which IPNs consist of both polymethacrylates and polyurethane (PU) networks, this article explores the polyaddition crosslinking reactions of multifunctional poly(methyl methacrylate- co -2-methacryloyloxyethyl isocyanate) [poly(MMA- co -MOI)] [MMA/MOI = 90/10] with various diols leading to PU network formation. Thus, the equimolar polyaddition crosslinking reactions of poly(MMA- co -MOI) with ethylene glycol (EG), 1,6-hexane diol, and 1,10-decane diol (DD) were carried out in N -methyl pyrrolidone at a 0.25 mol/L isocyanate group concentration at 80 °C. The second-order rate constants decreased from EG to DD. The deviation of the actual gel point from the theoretical one was smaller from EG to DD. The intrinsic viscosity of resulting prepolymer demonstrated almost no variation with progressing polymerization for the EG system, whereas it gradually increased with conversion for the DD system. Close to the gel point conversion it increased rather drastically for both systems. The swelling ratio of resulting gel was higher from EG to DD. These are discussed mechanistically in terms of the significant occurrence of intramolecular cyclization and intramolecular crosslinking reactions leading to shrinkage of the molecular size. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3243,3248, 2003 [source] Crosslinking polymerization leading to interpenetrating polymer network formation.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2003Abstract At the start of our research program concerned with the elucidation of the crosslinking polymerization mechanism leading to interpenetrating polymer network (IPN) formation, in which IPNs consist of both polymethacrylates and polyurethane (PU) networks, this article deals with the polyaddition crosslinking reaction leading to PU network formation. Therefore, 2-methacryloyloxyethyl isocyanate (MOI) was radically copolymerized with methyl methacrylate (MMA) in the presence of CBr4 as a chain-transfer agent. The resulting poly(MMA- co -MOI)s, having pendant isocyanate (NCO) groups as novel multifunctional polyisocyanates, were used for polyaddition crosslinking reactions with ethylene glycol as a typical diol. The second-order rate constants depended on both the functionality of poly(MMA- co -MOI) and the NCO group concentration. The actual gel points were compared with the theoretical ones calculated according to Macosko's equation; the deviation of the actual gel point from the theoretical value became more remarkable for a greater functionality of poly(MMA- co -MOI) and at a lower NCO group concentration or at a lower poly(MMA- co -MOI) concentration. These are discussed mechanistically, with consideration given to the significance of intramolecular cyclization and intramolecular crosslinking reactions leading to the shrinkage of the molecular size of the prepolymer, along with the data of the intrinsic viscosities of resulting prepolymers and the swelling ratios of resulting gels. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 606,615, 2003 [source] Immobilization of Toxic Metals in Solidified Systems of Siloxo-Sial NetworksJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2006Hanzlí The environmental contamination caused by waste toxic metals and their acidic solution could be inhibited in solidified systems of activated kaolinitic clays. Low-temperature synthesis of alkali-activated clay generates a siloxo-sial amorphous polymer network, which excels in its behavior of netting the toxic metals in it. The setting of inorganic polymers occurs at normal laboratory temperature and pressure. The obtained solid matter locks waste metals (copper, nickel, and cobalt) in the formatted network. Natural kaolinitic clay is also a waste product of clay mining, owing to its higher content of coloring metals,iron and titanium. [source] Synthesis of Au@SiO2 Core/Shell Nanoparticles and their Dispersion into an Acrylic Photocurable Formulation: Film Preparation and CharacterizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2008Marco Sangermano Abstract Au core/silica shell (Au@SiO2) nanoparticles were synthesized by coating gold NPs with sol/gel silica in alcoholic solution. The alcoholic dispersion was added, in the range of 1,5 wt.-%, to TPGDA and photocured by means of UV light. Transparent coatings were obtained and they can find suitable applications. It was shown that the NPs can restrict the segmental motion and decrease the free volume of the polymer network, with a consequent increase in glass transition temperature. TEM analysis put in evidence that the particles are well dispersed without any macroscopic agglomeration, and many particles are present as isolated particles. [source] Photochemically Cross-linked Poly(aryl ether ketone) RingsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 23 2006Ian Teasdale Abstract Summary: Macrocyclic phenyl ether ketones were prepared via pseudo high dilution condensation. Irradiation of these rings with UV light in a solution containing isopropyl alcohol as hydrogen donor resulted in a photo-induced reduction of benzophenone to benzopinacol and the formation linked macrocycles. These rings can be heated to undergo ring-opening polymerization and produce a polymer network or they can be added to a polycondensation reaction to prepare poly(ether ether ketones) with variable degrees of cross-linking. Photochemical cross-linking of PEK rings and ring opening polymerization (n: 2,6). (a) h,, iPrOH, DCM; (b) CsF, 260,°C (polymer 3); (c) 4,4,,difluorobenzophenone, hydroquinone, diphenylsulphone, K2CO3, 260,°C (2% polymer 4; 6% polymer 5). [source] Fabrication of Silver Nanoparticles in Hydrogel Networks,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2006Y. Murali Mohan Abstract Summary: This paper describes a simple and facile approach to fabricate well dispersed silver nanoparticles (AgNPs) in poly[N -isopropylacrylamide- co -(sodium acrylate)] hydrogels. The silver nanoparticles formed are spherical in shape with a narrow size distribution in the hydrogel networks in which the nanoparticles are stabilized by the polymer network. Uniformly dispersed silver nanoparticles were obtained with poly[N -isopropylacrylamide- co -[sodium acrylate)] hydrogels, whereas a poly(N -isopropylacrylamide)/poly(sodium acrylate) IPN gel showed aggregated nanoparticles. It is demonstrated that the hydrogel network structure determines the size and shape of the nanoparticles. These particles are more stable in the gel networks compared to other reduction methods. The hydrogel/silver nanohybrids were well characterized by XRD, UV-vis spectrometry, scanning electron microscopy and transmission electron microscopy. Schematic representation of the preparation of Ag nanoparticles in hydrogel networks. [source] Properties and interfacial bonding for regenerated cellulose,polyurethane/amylose acetate sipn composite filmsPOLYMER COMPOSITES, Issue 6 2000Jiahui Yu Composite films were obtained by placing a polyurethane/amylose acetate semi-interpenetrating polymer network (SIPN) coating onto the surfaces of regenerated cellulose (RC) film. The properties of the composite film, such as tensile strength, 79.9 MPa (in dry state), 49.5 MPa (in wet state), water resistance (R), 0.62, dimensional stability (Sc), 3.0%, and water vapor permeability (P), 5.96 × 10,5 Kgm,2h,1, are better than those of the uncoated RC film or RC film with PU coating. The interfacial strength was characterized with infrared spectroscopy (IR), ultraviolet spectroscopy (UV), transmission electron microscopy (TEM), and electron probe microanalysis (EPMA). The results showed the existence of covalent and hydrogen bonds between the SIPN coat layer and the RC layer. It was also found that the PU prepolymer in the coating layer penetrated into the cellulose bulk, and reacted with the cellulose molecules, which formed another SIPN. [source] Carrageenan- g -poly(acrylamide)/poly(vinylsulfonic acid, sodium salt) as a novel semi-IPN hydrogel: Synthesis, characterization, and swelling behaviorPOLYMER ENGINEERING & SCIENCE, Issue 9 2007Ali Pourjavadi A semi-interpenetrating polymer network (semi-IPN) hydrogel based on kappa-carrageenan (,C) and poly (vinylsulfonic acid, sodium salt) (PVSA) was prepared by graft copolymerization of acrylamide (AAm) using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. FTIR spectroscopy was used for confirming the structure of the final product. It was found that the chemical composition of the Semi-IPN hydrogel is equal to the initial homopolymers and monomer feed compositions. The swelling capacity of the hydrogel was shown to be affected by the MBA, APS, and AAm concentration as well as ,C/PVSA weight ratio. The swelling behavior of the hydrogel was also investigated in various pHs and salt solutions. Since the highly swelling biopolymer-based hydrogel exhibits low salt-sensitivity, it may be referred to as an anti-salt superabsorbent hydrogel. The swelling kinetics of the superabsorbent hydrogels was studied as well. POLYM. ENG. SCI., 47:1388,1395, 2007. © 2007 Society of Plastics Engineers [source] Effects of silicone rubber on properties of dielectric acrylate elastomer actuatorPOLYMER ENGINEERING & SCIENCE, Issue 10 2006G. Mathew This article describes the effects of silicone rubber (SR) networks on the actuating behavior of acrylate rubber (AR)-based dielectric actuators. SR chains were diffused into a swollen AR networks in the presence of a co-solvent, and then the silicone chains were chemically crosslinked in an attempt to form an interpenetrating polymer network. The presence of SR in the AR network was confirmed by various instrumental analyses including attenuated total reflectance-Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The total crosslink density based on a swelling method and tensile properties increased with modification time. The Maxwell stresses were also determined using a pure-shear specimen. They increased in a parabolic fashion with the applied voltage, and depended on the type of compliant electrode and SR used. POLYM. ENG. SCI. 46:1455,1460, 2006. © 2006 Society of Plastics Engineers. [source] Contribution of polymer chemistry to dentistry: development of an impermeable interpenetrating polymer network to protect teeth from acid demineralizationPOLYMER INTERNATIONAL, Issue 2 2008Nobuo Nakabayashi The purpose of this review article is to show how polymer science can contribute to the further improvement of modern dentistry. It has long been believed that the development of strong dental materials is essential to improve dentistry, and polymeric materials might not be reliable compared to metals and ceramics. It was hypothesized that the bonding of restoration materials to the tooth structure is required in order to inhibit the detachment of prostheses. However, bonding of artificial materials to natural tissues is difficult. It has been found that a polymer network interpenetrated with dental hard tissues resolves this problem, that formal bonding is not required and that protection of prepared dentin against lactic acid demineralization with an impermeable barrier is a requisite for prevention of caries. Copyright © 2007 Society of Chemical Industry [source] Synthesis, characterization, mechanical properties and biocompatibility of interpenetrating polymer network,super-porous hydrogel containing sodium alginatePOLYMER INTERNATIONAL, Issue 12 2007Lichen Yin Abstract In this investigation an interpenetrating polymer network,superporous hydrogel containing sodium alginate (IPN-SPHAlg) was synthesized. The morphology of the polymer was characterized using scanning electron microscopy, light images and porosity, and the polymer was further examined by swelling ratio, mechanical strength and biocompatibility. The results indicated that the IPN-SPHAlg possessed both large numbers of interconnected pores and an interpenetrating network. The swelling ratio of IPN-SPHAlg was lower than that of the superporous hydrogel (SPH) and it decreased as the sodium alginate/monomer ratio increased. The IPN-SPHAlg exhibited pH responsiveness and salt-sensitive properties. Compared to SPH and SPH composites, the mechanical strength of IPN-SPHAlg was significantly enhanced. Thiazolyl blue assay on AD293 cells, in situ lactate dehydrogenase assay and morphological study of rat intestine showed that the polymer induced no significant cell or mucosal damage. The fast swelling, good mechanical properties, pH sensitivity and biocompatibility of the IPN-SPHAlg suggested it as a potential candidate in the field of drug-delivery systems. Copyright © 2007 Society of Chemical Industry [source] Light-induced crosslinking polymerization,POLYMER INTERNATIONAL, Issue 11 2002Christian Decker Abstract Light-induced polymerization of multifunctional monomers is a powerful method to transform a liquid resin into a solid polymer almost instantly, selectively in the illuminated areas. The reaction can conveniently be followed by real-time infrared spectroscopy, a technique which records directly conversion versus time curves in photosensitive resins undergoing ultrafast curing upon UV or laser exposure. The photoinitiator was shown to play a key role in laser-induced polymerization because of the monochromatic character of the emitted radiation. By using highly sensitive acrylate photoresists, relief images of micronic size were obtained by fast scanning with a focused laser beam. The laser direct imaging technology makes image transfer obsolete and eliminates the manufacture of photolithographic masks. Polymer networks of different architectures have been obtained by UV irradiation of various monomer blends: acrylate,epoxide, acrylate,vinyl ether, acrylate,polyene, vinyl ether,maleate and thiol,polyene. With monomers polymerizing by different mechanisms, ie radical and cationic types, interpenetrating polymer networks have been generated upon UV exposure in the presence of adequate photoinitiators. The crosslinking reaction was also performed in the solid state on polybutadiene which was plasticized with a multifunctional acrylate or thiol monomer. Thermoplastic elastomers were transformed within a fraction of a second into an insoluble material showing a greatly improved resistance to heat and chemicals, because of the tight polymer network formed. © 2002 Society of Chemical Industry [source] | ||||||||||||||||||||||||||||