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Gelling System (gelling + system)

Distribution by Scientific Domains
Polymers and Materials Science60%

Selected Abstracts

Novel Gelling Systems of , -, , - and , -Carrageenans and their Composite Gels with Cellulose Using Ionic Liquid

MACROMOLECULAR BIOSCIENCE, Issue 4 2009
Kamalesh Prasad
Abstract Gels of three types of carrageenans (, -, , - and , -), as well as their composite gels with cellulose, were prepared using an ionic liquid, 1-butyl-3-methylimidazolium chloride (BMIMCl), by a heating-cooling process. , -Carrageenan gave the formation of hard gel while the other two carrageenans gave the formation of softer gels with BMIMCl. The gels were characterized by X-ray diffraction (XRD), thermal analysis (TGA and DSC), scanning electron microscope (SEM) and compressive testing. The results indicated that, among the three types of carrageenans, , - and , -carrageenans gave better miscible gels with BMIMCl, followed by , -carrageenan. On the other hand, , -carrageenan gave a better miscible composite gel with cellulose and BMIMCl, followed by , - and , -carrageenans. The stress-strain curves indicated that the mechanical properties of the above gel systems on the compressive mode were much better than those of the hydrogels of , - and , -carrageenans as well as the cellulose gel with BMIMCl. [source]

Architecture of Supramolecular Soft Functional Materials: From Understanding to Micro-/Nanoscale Engineering

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010
Jing-Liang Li
Abstract This article gives an overview of the current progress of a class of supramolecular soft materials consisting of fiber networks and the trapped liquid. After discussing the up-to-date knowledge on the types of fiber networks and the correlation to the rheological properties, the gelation mechanism turns out to be one of the key subjects for this review. In this concern, the following two aspects will be focused upon: the single fiber network formation and the multi-domain fiber network formation of this type of material. Concerning the fiber network formation, taking place via nucleation, and the nucleation-mediated growth and branching mechanism, the theoretical basis of crystallographic mismatch nucleation that governs fiber branching and formation of three-dimensional fiber networks is presented. In connection to the multi-domain fiber network formation, which is governed by the primary nucleation and the subsequent formation of single fiber networks from nucleation centers, the control of the primary nucleation rate will be considered. Based on the understanding on the the gelation mechanism, the engineering strategies of soft functional materials of this type will be systematically discussed. These include the control of the nucleation and branching-controlled fiber network formation in terms of tuning the thermodynamic driving force of the gelling system and introducing suitable additives, as well as introducing ultrasound. Finally, a summary and the outlook of future research on the basis of the nucleation-growth-controlled fiber network formation are given. [source]

Architecture of Supramolecular Soft Functional Materials: From Understanding to Micro-/Nanoscale Engineering

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2010
Jing-Liang Li
Abstract This article gives an overview of the current progress of a class of supramolecular soft materials consisting of fiber networks and the trapped liquid. After discussing the up-to-date knowledge on the types of fiber networks and the correlation to the rheological properties, the gelation mechanism turns out to be one of the key subjects for this review. In this concern, the following two aspects will be focused upon: the single fiber network formation and the multi-domain fiber network formation of this type of material. Concerning the fiber network formation, taking place via nucleation, and the nucleation-mediated growth and branching mechanism, the theoretical basis of crystallographic mismatch nucleation that governs fiber branching and formation of three-dimensional fiber networks is presented. In connection to the multi-domain fiber network formation, which is governed by the primary nucleation and the subsequent formation of single fiber networks from nucleation centers, the control of the primary nucleation rate will be considered. Based on the understanding on the the gelation mechanism, the engineering strategies of soft functional materials of this type will be systematically discussed. These include the control of the nucleation and branching-controlled fiber network formation in terms of tuning the thermodynamic driving force of the gelling system and introducing suitable additives, as well as introducing ultrasound. Finally, a summary and the outlook of future research on the basis of the nucleation-growth-controlled fiber network formation are given. [source]

Sustained ophthalmic in situ gel of ketorolac tromethamine: rheology and in vivo studies

DRUG DEVELOPMENT RESEARCH, Issue 6 2009
A.S. Manjappa
Abstract Most ocular diseases are treated with topical eye drops. The poor bioavailability and therapeutic response exhibited by these conventional eye drops due to rapid precorneal elimination of the drug may be overcome by the use of in situ gelling systems that are instilled as drops into the eye and undergo a sol-to-gel transition in the cul-de-sac. The present work describes the formulation and evaluation of an ophthalmic delivery system of the nonsteroidal anti-inflammatory drug (NSAID), ketorolac tromethamine, based on the concept of pH-triggered in situ gelation. Polyacrylic acid (Carbopol® 934) was used as the gelling agent in combination with hydroxypropylmethylcellulose (Methocel E15LV), which acted as a viscosity enhancer. The prepared formulations were characterized for clarity, pH, drug content, rheology, and in vivo drug release. Clarity, pH, and drug content of the developed formulations were found to be satisfactory. The developed formulation showed pseudo-plastic rheology. The formulation with benzalkonium chloride and edetate disodium improved the rate of corneal absorption but not the extent. The developed formulation is a viable alternative to conventional eye drops by virtue of its ability to enhance bioavailability through its longer precorneal residence time and ability to sustain drug release. Also importantly is the ease of instillation afforded and decreased frequency of instillation resulting in better patient acceptance. Drug Dev Res, 2009. © 2009 Wiley-Liss, Inc. [source]

Dynamical scaling in fractal structures in the aggregation of tetraethoxysilane-derived sonogels

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5-1 2010
Dimas R. Vollet
Dynamical scaling properties in fractal structures were investigated from small-angle X-ray scattering (SAXS) data of the kinetics of aggregation in silica-based gelling systems. For lack of a maximum in the SAXS intensity curves, a characteristic correlation distance , was evaluated by fitting a particle scattering factor model valid for polydisperse coils of linear chains and f -functional branched polycondensates in solution, so the intensity at q = ,,1, I(,,1, t), was considered to probe dynamical scaling properties. The following properties have been found: (i) the SAXS intensities corresponding to different times t, I(q, t), are given by a time-independent function F(q,) = I(q, t),,D/Q, where the scattering invariant Q has been found to be time-independent; (ii) , exhibited a power-law behavior with time as ,,t,, the exponent , being close to 1 but diminishing with temperature; (iii) I(,,1, t) exhibited a time dependence given by I(,,1, t) ,t,, with the exponent , found to be around 2 but diminishing with temperature, following the same behavior as the exponent ,. In all cases, ,/, was quite close to the fractal dimension D at the end of the studied process. This set of findings is in notable agreement with the dynamical scaling properties. [source]