Formation of Gels in Ethylcellulose Solutions. An Interpretation from Dynamic Viscoelastic Results

Lizaso, Eli; Muñoz, Manuel López; Santamaría, Antxón

doi:10.1021/ma9812231

Cited by 28 publications

(38 citation statements)

References 37 publications

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“…On the contrary, for SMS-based oleogels, an extensive plateau region is only apparent for the oleogel containing the highest SMS concentration evaluated (20% w/w). At lower concentrations, a crossover between both SAOS functions (which is shifted to lower frequencies as SMS concentration decreases), and similar values for both linear viscoelasticity functions, indicative of weak gels (Lizaso et al, 1999;Heng et al, 2005), are observed ( Figure 2a). As a consequence, relatively high values of the loss tangent are obtained for 10% and 15% w/w SMS concentrations (Figure 2b).…”

Section: Linear Viscoeslasticity A) Influence Of Processing Thermal Pmentioning

confidence: 61%

Rheology of oleogels based on sorbitan and glyceryl monostearates and vegetable oils for lubricating applications

Sánchez¹,

Franco²,

Delgado³

et al. 2011

Grasas y Aceites

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Oleogels based on sorbitan and glyceryl monostearates and different types of vegetable oils, potentially applicable as biodegradable alternatives to traditional lubricating greases, have been studied. In particular, the rheological behavior, by means of small-amplitude oscillatory shear (SAOS) measurements, and some lubrication performance-related properties (mechanical stability and tribological response) have been evaluated in this work. SAOS response and mechanical stability of these oleogels are significantly influenced by the type and concentration of the organogelator and the vegetable oil used in the formulations. Glyceryl monostearate (GMS) generally produces stronger gels than sorbitan monostearate (SMS). The use of low-viscosity oils, such as rapeseed and soybean oils, yields gels with significantly higher values of the linear viscoelastic functions than oleogels prepared with high-viscosity oils, i.e. castor oil. The rheological behavior of SMS-based oleogels also depends on the cooling rate applied during the gelification process. On the other hand, the oleogels studied present low values of the friction coefficient obtained in a tribological contact, although only some GMS/castor oil-based oleogels exhibit a suitable mechanical stability.<br><br>En el presente trabajo se han estudiado diferentes oleogeles, basados en monoestearatos de sorbitano y glicerilo y aceites vegetales, que podrían ser potencialmente empleados como alternativas biodegradables a las grasas lubricantes tradicionales. En concreto, se ha evaluado su comportamiento reológico, a través de ensayos en cizalla oscilatoria, y algunas propiedades relacionadas con su rendimiento en la lubricación, tales como su estabilidad mecánica y comportamiento tribológico. La respuesta reológica y la estabilidad mecánica de los oleogeles estudiados están significativamente influenciadas por el tipo y la concentración del agente gelificante y por el aceite vegetal empleado. Así, el monoestearato de glicerilo (GMS) produce, generalmente, geles más fuertes que el monoestearato de sorbitano (SMS). El uso de aceites de baja viscosidad, como los aceites de colza o de soja, dan lugar a geles con valores más altos de las funciones viscoelásticas lineales que los oleogeles preparados con aceite de ricino. El comportamiento reológico de los oleogeles de SMS depende, además, de la velocidad de enfriamiento durante la gelificación. Por otra parte, los oleogeles estudiados presentan bajos valores del coeficiente de fricción, determinado en un contacto tribológico, aunque sólo algunos oleogeles que contienen GMS y aceite de ricino muestran una estabilidad mecánica adecuada

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Section: Linear Viscoeslasticity A) Influence Of Processing Thermal Pmentioning

confidence: 61%

Rheology of oleogels based on sorbitan and glyceryl monostearates and vegetable oils for lubricating applications

Sánchez¹,

Franco²,

Delgado³

et al. 2011

Grasas y Aceites

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“…Nonaqueous gel formulations have been a useful vehicle for moisture-sensitive drugs for topical and transdermal application (20)(21)(22)(23)(24). Critical components for the successful development of a semisolid product for topical and transdermal applications include the stability of the active pharmaceutical ingredient (API) in the delivery matrix, product uniformity, and the release profile of API from the delivery matrix.…”

Section: Discussionmentioning

confidence: 99%

“…The major degradation pathway involved with moisture-sensitive drugs is hydrolysis followed by secondary degradation reactions such as polymerization and isomerization (19). In contrast to extensive research on traditional semisolid dosage forms such as creams, ointments, and hydrogels, there are far fewer reports on the development of nonaqueous gel matrices intended for topical and transdermal drug delivery (20)(21)(22)(23)(24). Ethyl cellulose is frequently used as a gelling agent for nonaqueous gel vehicles.…”

Section: Introductionmentioning

confidence: 99%

“…Lee and colleagues developed a nonaqueous gel with 3-10% (% w/w) ethyl cellulose dispersed in an ethanol/tricaprylin (40:60, w/w) mixture (21). Lizaso and coworkers heated ethyl cellulose and phthalate ester derivative mixtures to 180°C and formed a nonaqueous gel during the cooling process (22). The Heng group reported on nonaqueous gel matrices containing ethyl cellulose and Miglyol 840®, which is a mixture of propylene glycol dicaprylate and dicaprate, obtained by directly mixing the ethyl cellulose and Miglyol 840 at 60°C (23).…”

Section: Introductionmentioning

confidence: 99%

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Nonaqueous Gel for the Transdermal Delivery of a DTPA Penta-ethyl Ester Prodrug

Zhang

Sadgrove

Sueda

et al. 2013

AAPS J

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Abstract. Diethylenetriamine pentaacetic acid penta-ethyl ester, designated as C2E5, was successfully incorporated into a nonaqueous gel for transdermal delivery. The thermal and rheological properties of a formulation containing 40% C2E5, 20% ethyl cellulose, and 40% Miglyol 840® prepared using the solvent evaporation method demonstrated that the gel had acceptable content uniformity and flow properties. In vitro studies showed that C2E5 was steadily released from the gel at a rate suitable for transdermal delivery. Topical application of the gel at a 200 mg C2E5/kg dose level in rats achieved significantly higher plasma exposures of several active metabolites compared with neat C2E5 oil at the same dose level. The results suggest that transdermal delivery of a chelator prodrug is an effective radionuclide decorporation strategy by delivering chelators to the circulation with a pharmacokinetic profile that is more consistent with the biokinetic profile of transuranic elements in contaminated individuals.

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“…Debrières et al investigated the thermal gelation of methyl cellulose (MC) with an appropriate degree of substitution (DS) and the results showed that the gelation was thermoreversible and attributed to hydrophobic interactions (Desbrières et al 2000). Thermoreversible gelation, i.e., formation of clear gel and its melting on cooling has been reported for aqueous ethylcellulose (EC)/diester phthalate solutions (Lizaso et al 1999). The presence of two carbonyl (C=O) groups in diester phthalates for each molecule allowed the solvent to act as a bridge between EC chains.…”

Section: Introductionmentioning

confidence: 99%

Rheological behavior of cyanoethyl celluloses in aqueous solutions

Zhou

Zhang

2012

Cellulose

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Water-soluble cyanoethyl cellulose (CEC) samples were synthesized by homogeneous reaction of cellulose with acrylonitrile in LiOH/urea aqueous solutions. The dynamic viscoelastic property of CEC with different degree of substitution (DS) in water at different temperatures and concentrations were investigated. At low concentrations, the CEC solutions displayed liquid-like behavior with G 0 smaller than G 00 at low frequencies; while the curves of G 0 and G 00 intersected at the middle of the frequency range at higher concentration, indicating an existence of chain aggregation and entanglement network. The gelation temperature (T gel ) was determined from the point of intersection in tan d versus temperature (T) at different frequencies, indicating the validity of Winter-Chambon criteria. It was found that T gel increased with increasing DS, and that the exponent (n) values at the gel point decreased with increasing DS. The heatingcooling process proved that the sol-gel transition for CECs in water was thermally irreversible. The AFM images revealed that the particles packed loosely together to form gel aggregates. Moreover, the Maxwell model with four elements was used to describe the frequency dependencies of G 0 and G 00 for CEC in aqueous solution.

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Formation of Gels in Ethylcellulose Solutions. An Interpretation from Dynamic Viscoelastic Results

Cited by 28 publications

References 37 publications

Rheology of oleogels based on sorbitan and glyceryl monostearates and vegetable oils for lubricating applications

Rheology of oleogels based on sorbitan and glyceryl monostearates and vegetable oils for lubricating applications

Nonaqueous Gel for the Transdermal Delivery of a DTPA Penta-ethyl Ester Prodrug

Rheological behavior of cyanoethyl celluloses in aqueous solutions

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