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Polymer Gels (polymer + gel)

Distribution by Scientific Domains

Polymers and Materials Science	58%
Chemistry	25%

Terms modified by Polymer Gels

polymer gel electrolyte

Selected Abstracts

Novel Method of Producing Polymer Gels in Aqueous Solution Using UV Irradiation

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2004
Fumiyoshi Ikkai
Abstract Summary: We developed a novel method of producing polymer gels in aqueous solution using UV irradiation. Persulfates were effective photosensitive initiators of polymerization and/or gelation of acryloyl-type monomers/polymers. The gelation was confirmed by an abrupt increase in light scattering intensity, ,I(q),T, at the gelation point. The gelation method entails significant advantages: it does not need any cross-linkers, temperature control (heating), and additives except the persulfate. The UV irradiation time dependence of light scattering intensity, ,I(q),T, for pre-gel solutions containing N -isopropylacrylamide (NIPAm) and/or ammonium persulfate (APS). [source]

Ground-State Equilibrium Thermodynamics and Switching Kinetics of Bistable [2]Rotaxanes Switched in Solution, Polymer Gels, and Molecular Electronic Devices

CHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006
Jang Wook Choi
Abstract We report on the kinetics and ground-state thermodynamics associated with electrochemically driven molecular mechanical switching of three bistable [2]rotaxanes in acetonitrile solution, polymer electrolyte gels, and molecular-switch tunnel junctions (MSTJs). For all rotaxanes a ,-electron-deficient cyclobis(paraquat- p -phenylene) (CBPQT4+) ring component encircles one of two recognition sites within a dumbbell component. Two rotaxanes (RATTF4+ and RTTF4+) contain tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) recognition units, but different hydrophilic stoppers. For these rotaxanes, the CBPQT4+ ring encircles predominantly (>90,%) the TTF unit at equilibrium, and this equilibrium is relatively temperature independent. In the third rotaxane (RBPTTF4+), the TTF unit is replaced by a ,-extended analogue (a bispyrrolotetrathiafulvalene (BPTTF) unit), and the CBPQT4+ ring encircles almost equally both recognition sites at equilibrium. This equilibrium exhibits strong temperature dependence. These thermodynamic differences were rationalized by reference to binding constants obtained by isothermal titration calorimetry for the complexation of model guests by the CBPQT4+ host in acetonitrile. For all bistable rotaxanes, oxidation of the TTF (BPTTF) unit is accompanied by movement of the CBPQT4+ ring to the DNP site. Reduction back to TTF0 (BPTTF0) is followed by relaxation to the equilibrium distribution of translational isomers. The relaxation kinetics are strongly environmentally dependent, yet consistent with a single electromechanical-switching mechanism in acetonitrile, polymer electrolyte gels, and MSTJs. The ground-state equilibrium properties of all three bistable [2]rotaxanes were reflective of molecular structure in all environments. These results provide direct evidence for the control by molecular structure of the electronic properties exhibited by the MSTJs. [source]

Testing automated liquid-based cytology samples with a manual liquid-based cytology method using residual cell suspensions from 500 ThinPrep cases

DIAGNOSTIC CYTOPATHOLOGY, Issue 6 2006
John A. Maksem M.D.
Abstract We report a technical improvement upon a previously disclosed manual liquid-based cytology (MLBC) method; and, we use the improved method to prepare slides from residual ThinPrep specimens in order to see how often ThinPrep diagnoses correspond to diagnoses derived from exhaustive examination of their parent sample suspensions. Residual cell suspensions from 500 ThinPrep cases comprising (1) 20 low-grade squamous intraepithelial lesions (LSILs); (2) 200 high risk (HR) negatives and 20 ASC-US; and (3) 260 screening cytology specimens were studied. Institutional review committee guidelines allowed us to know diagnoses by groups of specimens, but did not allow us to know individual patient diagnoses, so we could not perform case-by-case matched outcome-comparisons. Cells were concentrated by conventional centrifugation and sedimented into a polymer gel that was then vortex-mixed and converted into a viscous cell-rich suspension. The cell suspension was smeared between two clean glass slides, which were air-dried and stained with the Papanicolaou stain. Two study-sets were created, comprising one slide from each case. Each of the two study sets was examined by two cytopathologists, and discordant diagnoses were adjudicated. Because of the ambiguity involved in the "atypical" (ASC-US, ASC-H, AGC) diagnosis categories, only outcomes at the level of LSIL or greater were recorded. All MLBC SILs were digitally imaged and abnormal slides plus digital images were sent to the laboratory that provided the residual automated liquid-based cytology (ALBC) suspensions. The final diagnoses were confirmed by the laboratory that provided the residual ALBC specimens. MLBC slides of the 20 LSIL cases afforded 2 high-grade squamous intraepithelial lesions (HSILs) and 18 LSILs. Those of the 200 HR-Negatives showed 3 HSILs and 30 LSILs; and those of the 20 HR-ASC-US showed 3 HSILs and 9 LSILs. MLBC slides of the 260 screening cytology specimens showed 1 Carcinoma, 3 HSILs and 20 LSILs; affording 3 HSILs and 14 LSILs more than originally diagnosed. The MLBC method of this report is useful for preparing cell suspensions for cytological examination. Our analytical method was exhaustive and used nearly all of the cell material that was provided to us for analysis; therefore, we conclude that this approach is useful for determining how well ALBC instruments represent their parent sample suspensions. It appears that "rare events" may be overlooked when limited sample aliquots are analyzed by ALBC instruments, and this probably accounts for our increased discovery of SILs by the MLBC method. Also, SILs often present as aggregates of cohesive cells which, if overlooked or ineffectively transferred to ALBC slides, would not be diagnosed. Diagn. Cytopathol. 2006;34:391,396. © 2006 Wiley-Liss, Inc. [source]

Chemical-to-Electrical-Signal Transduction Synchronized with Smart Gel Volume Phase Transition

ADVANCED MATERIALS, Issue 43 2009
Akira Matsumoto
A stimulus-responsive polymer gel designed on a field-effect transistor gate undergoes a reversible volume phase transition in response to a specific biomolecule. An abrupt permittivity change at the gel/gate interface during the transition gives rise to a chemical to electrical signal conversion; the signal is thus detectable via a transistor without the limit of the Debye length. [source]

Repair of segmental defects in rabbit humeri with titanium fiber mesh cylinders containing recombinant human bone morphogenetic protein-2 (rhBMP-2) and a synthetic polymer

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2002
Narumichi Murakami
Abstract To develop a new technology that enhances the regeneration potential of bone and the repair of large intercalated defects in long bone, recombinant human bone morphogenetic protein-2 (BMP-2; 20 ,g or 40 ,g) was mixed in a polymer gel (poly-lactic acid-polyethyleneglycol block copolymer; PLA-PEG; 200 mg) and incorporated into titanium fiber-mesh cylinders. Three 5-mm cylinders were placed end-to-end to fill a 15-mm defect created in the humeri of adult rabbits and were stabilized by an intramedullary rod. In controls, the titanium fiber-mesh cylinders were combined with PLA-PEG in the absence of BMP. Six weeks after implantation, new bone had formed on the surface of the implant and had bridged the defect. All of the defects (5/5) treated by cylinders containing 120 ,g (40 ,g × 3) of BMP were repaired completely. New bone formation was also found inside the pores of the cylinders. The defect was not repaired in the control animals. These results demonstrate that these new composite implants fabricated by combining rhBMP, synthetic degradable polymers and compatible biomaterials enhance the regeneration potential of bone. Thus, it is possible that large skeletal defects can be repaired using this prosthesis in lieu of autogenous bone graft. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 62: 169,174, 2002 [source]

Low-frequency dielectric spectroscopy as a tool for studying the compatibility between pharmaceutical gels and mucous tissue

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2003
Helene HäGerström
Abstract This interdisciplinary work demonstrates how low-frequency dielectric spectroscopy, a technique that is frequently used within physics, can be used to assess the possibilities of intimate surface contact between a polymer gel and mucous tissue, which is generally considered to be the first step in the mucoadhesion process. The dielectric responses of five different gels, of freshly excised porcine nasal mucosa and of systems made by combining the two were measured. All spectra were modeled by a Randles electric circuit containing a diffusion element, a barrier resistance in parallel with a capacitance, and a high-frequency resistance. The results were used to create a measure of the compatibility between the gel and the mucus, which we have named the compatibility factor. Thus, the compatibility factor provides us with a measure of the ease with which a charged species passes the interface between a gel and the mucus layer. The compatibility factor is calculated from the high frequency (kHz region) response of the gel, of the mucosa, and of the combined system. The two highest compatibility factors in this study were obtained for gels based on crosslinked poly(acrylic acid) and chitosan, which was in agreement with the results from mucoadhesion measurements that were performed using a tensile strength method. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1869,1881, 2003 [source]

Novel Method of Producing Polymer Gels in Aqueous Solution Using UV Irradiation

Measurement of aroma compound self-diffusion in food models by DOSY

MAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2004
Thierry Gostan
Abstract Self-diffusion measurement of solutes in polymer gels has been investigated using pulsed gradient spin echo NMR spectroscopy. However, few data are available on the self-diffusion of small solutes in natural polysaccharide polymers used as thickeners in the food industry. Since aroma diffusion in food matrices could have an impact on flavor release, this is an interesting and economic challenge. Diffusion ordered spectroscopy (DOSY) resolves diffusion data for each component in complex mixtures. We used DOSY with the inverse Laplace transform approach with the maximum entropy algorithm to investigate diffusion of two aroma compounds, ethyl butanoate and linalool, in an ,-carrageenan matrix as the food model. We showed that the self-diffusion coefficient values of small molecules in a polysaccharide matrix could be easily extracted using this method. We then investigated the impact of the gelling state of ,-carrageenan matrices on the self-diffusion of ethyl butanoate. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Electrically adjustable thermotropic windows based on polymer gels

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2003
Tamás Gyenes
Abstract Several attempts have been made recently in order to develop "Smart" windows, which can moderate light and heat intensities. Based upon the phase transitions of polymer gels, a novel electrically adjustable window, which includes a gel layer, has been developed in our laboratory. Unlike other electrically controlled structures, the optical properties of the gel layer are abruptly modified by the Joule heat of audio frequency AC current. The so-called "gel-glass" becomes opaque when the temperature exceeds a critical value and changes back to its original transparent state when it is cooled down again. This method results in fast control and relatively low operational cost. Two types of gel-glasses,active and passive structures,have been developed and investigated. In this paper, we demonstrate the structural build-up and working of these novel electrically adjustable thermotropic windows. Experimental studies have been made at different frequencies and voltages. The optical properties, as well as the energy balance of the systems, have been reported. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Chromogenic polymer gels for reversible transparency and color control with temperature at a constant volume

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2002
A. Seeboth
Abstract The preparation and characterization of novel chromogenic materials has developed extremely rapid in the last years. Among them, thermotropic and thermochromic polymer gel networks have met with growing interest, because of their advanced properties. These novel polymer gels exhibit pronounced changes in transparency and/or color intensity in a practically relevant temperature range. For many future technical applications it is an essential condition, that the volume of the used gel materials is independent of temperature. A current overview of this field is given. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Understanding the properties of aerobic sludge granules as hydrogels

BIOTECHNOLOGY & BIOENGINEERING, Issue 5 2009
Thomas Seviour
Abstract Aerobic sludge granules are larger, denser microbial aggregates than activated sludge flocs with a smoother and more regular surface, which facilitates greater wastewater treatment intensity. Factors important in their growth are still poorly understood, which is an impediment to the construction and operation of full-scale aerobic sludge granule processes. Data in this article obtained with granules treating an abattoir wastewater provide evidence that aerobic sludge granules are hydrogels. The results also demonstrate a method for characterizing macromolecular associations. The rheological profile of these granules was found to be analogous with that of typical polymer gels. Water uptake or swelling reflects an equilibrium between granule elastic modulus and osmotic pressure, whereby uptake is increased by reducing solute concentration or the elastic modulus. A weakening of the extracellular polymeric substance (EPS) matrix as demonstrated with mechanical spectroscopy was induced by several environmental factors including temperature, pH and ionic strength. Uniform and elastic deformation was observed at low strain. Enzymatic degradation studies indicate that proteins and ,-polysaccharides were the major granule structural materials. The aerobic sludge granules in the current study were therefore protein,polysaccharide composite physical hydrogels. While aerobic sludge granules treating an abattoir wastewater are used as a case study, many of the fundamental principles detailed here are relevant to other granulation processes. The paradigm established in this study can potentially be applied to better understand the formation of aerobic sludge granules and thus overcome a hurdle in the acceptance of aerobic sludge granulation as an alternative to more traditional wastewater treatment processes. Biotechnol. Bioeng. 2009;102: 1483,1493. © 2008 Wiley Periodicals, Inc. [source]