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Relationship between Rheological Properties and One-Step W/O/W Multiple Emulsion Formation

MORAIS, Jacqueline M.; ROCHA-FILHO, Pedro A.; BURGESS, Diane J.
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.07%
Formation of a normal (not temporary) W/O/W multiple emulsion via the one-step method as a result of the simultaneous occurrence of catastrophic and transitional phase inversion processes has been recently reported. Critical features of this process include the emulsification temperature (corresponding to the ultralow surface tension point), the use of a specific nonionic surfactant blend and the surfactant blend/oil phase ratio, and the addition of the surfactant blend to the oil phase. The purpose of this study was to investigate physicochemical properties in an effort to gain a mechanistic understanding of the formation of these emulsions. Bulk, surface, and interfacial theological properties of adsorbed nonionic surfactant (CremophorRH40 and Span80) films were investigated under conditions known to affect W/O/W emulsion formation. Bulk viscosity results demonstrated that CremophorRH40 has a higher mobility in oil compared than in water, explaining the significance of the solvent phase. In addition, the bulk viscosity profile of aqueous solutions containing CremophorRH40 indicated a phase transition at around 78 +/- 2 degrees C, which is in agreement with cubic phase formation in the Winsor III region. The similarity in the interfacial elasticity values of CremophorRH40 and Span80 indicated that canola oil has a major effect on surface activity...

Influence of Phase Inversion on the Formation and Stability of One-Step Multiple Emulsions

MORAIS, Jacqueline M.; ROCHA-FILHO, Pedro A.; BURGESS, Diane J.
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.27%
A novel method of preparation of water-in-oil-in-micelle-containing water (W/O/W(m)) Multiple emulsions using the one-step emulsification method is reported. These multiple emulsions were normal (not temporary) and stable over a 60 day test period. Previously, reported multiple emulsion by the one-step method were abnormal systems that formed at the inversion point of simple emulsion (where there is an incompatibility in the Ostwald and Bancroft theories, and typically these are O/W/O systems). Pseudoternary phase diagrams and bidimensional process-composition (phase inversion) maps were constructed to assist in process and composition optimization. The surfactants used were PEG40 hydrogenated castor oil and sorbitan oleate, and mineral and vegetables oils were investigated. Physicochemical characterization studies showed experimentally, for the First time, the significance of the ultralow surface tension point oil multiple emulsion formation by one-step via phase inversion processes. Although the significance of ultralow surface tension has been speculated previously, to the best of our knowledge, this is the first experimental confirmation. The multiple emulsion system reported here was dependent not only upon the emulsification temperature...

Babassu Nanoemulsions Have Physical and Chemical Stability

Gumiero, Viviane Cristina; da Rocha Filho, Pedro Alves
Fonte: TAYLOR & FRANCIS INC; PHILADELPHIA Publicador: TAYLOR & FRANCIS INC; PHILADELPHIA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.13%
Babassu is considered one of the greatest native resources in the world and its oil is used in body and hair formulations. The aim of this study was to evaluate the short-term stability in oil-in-water (O/W) nanoemulsions containing babassu oil prepared by emulsification phase inversion submitted to the centrifugation, thermal stress, and heating/cooling cycle tests. The formulations showed no change compared to the droplet size, polydispersity index, pH, and electrical conductivity values after thermal stress and heating/cooling cycle tests. Based on these results, the nanoemulsions obtained can be considered as promising disperse systems for pharmaceutical and cosmetic applications.; Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES); CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior); Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)

Desenvolvimento e avaliação do processo de obtenção de emulsões múltiplas A/O/A em etapa única empregando óleo de canola e tensoativo não iônico derivado do óleo de rícino; Development and evaluation of the production process of multiple emulsions W/O/W by one step employing canola oil and derivative castor oil non ionic surfactant

Morais, Jacqueline Moreira de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 04/06/2008 PT
Relevância na Pesquisa
46.12%
As emulsões múltiplas mostram-se como veículos promissores em várias áreas das ciências cosmética e farmacêutica. O estudo do método de obtenção de emulsões múltiplas em etapa única é ferramenta útil para elucidação de seus aspectos físico-químicos e para viabilizar sua aplicação tecnológica. O objetivo da pesquisa foi desenvolver e caracterizar os aspectos físico-químicos do processo de emulsificação em etapa única, das emulsões múltiplas A/O/A obtidas e dos tensoativos empregados. Testes preliminares de estabilidade e avaliação do seu perfil de liberação (cafeína) foram realizados. Nanoemulsões foram inicialmente obtidas pela metodologia proposta, resultado de processo de emulsificação por inversão de fases. Suas características físico-químicas foram determinadas (valores de pH, potencial zeta e granulometria) e a influência de aditivos avaliada. Para o desenvolvimento da emulsão múltipla foram realizadas análises qualitativas e quantitativas das variáveis relevantes à composição (tipo de fase oleosa, de tensoativo hidrofílico, valor de EHL, emprego de diagrama ternário) e ao método de emulsificação (temperatura de aquecimento das fases e de emulsificação, ordem de adição e velocidade de agitação). Os estudos das propriedades físico-químicas dos tensoativos e do filme interfacial formado (cloud point...

Produção e caracterização de membranas de microfiltração e ultrafiltração pelo método de inversão de fases, utilizando polisulfona como matéria-prima.; Production and characterization of microfiltration and ultrafiltration membranes via phase inversion process employing polysulfone as raw material.

Pucca, Paulo Tadeu Pimentel
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/10/2010 PT
Relevância na Pesquisa
45.92%
A presente pesquisa consistiu em produzir membranas sintéticas pelo processo de inversão de fases via precipitação por imersão e levantar dados operacionais relativos ao preparo das soluções poliméricas e respectivos espalhamentos sobre um suporte inerte, de forma a obter-se membranas uniformes, livres de imperfeições que possam afetar seu desempenho. Tal uniformidade requer a produção de soluções poliméricas homogêneas, sem a presença de bolhas, isentas de sólidos em suspensão e com viscosidade adequada, para que o filme espalhado com espessura controlada se mantenha íntegro até o momento da solidificação do polímero, que formará as membranas propriamente ditas. Para condução dos experimentos utilizou-se a polisulfona como polímero, a N-metil- 2 pirrolidona como solvente, não-tecido em poliéster como suporte inerte e água desmineralizada como não-solvente. As soluções foram preparadas com concentrações de cerca de 15 %, 20 % e 25 % em massa de polímero e imersas em banhos de coagulação contendo água desmineralizada a temperaturas de aproximadamente 23°C, 40°C e 50°C. As membranas obtidas após precipitação foram enxaguadas em água desmineralizada morna e então avaliadas morfologicamente através de microscopia eletrônica de varredura...

Avaliação da atividade antifúngica de óleo essencial de orégano (Origanum vulgare) nanoemulsionado e estudo de caso em queijo Minas Padrão; Evaluation of antifungal activity of nanoemulsions encapsulating oregano essential oil and case study in Minas Padrão cheese

Serna, Carolina Maria Bedoya
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/05/2015 PT
Relevância na Pesquisa
45.92%
Este trabalho de Mestrado teve por objetivo avaliar a atividade antifúngica in vitro e em queijo Minas Padrão de duas formulações (A e B) de nanoemulsões encapsulando óleo essencial de orégano (Origanum vulgare) produzidas pelo método da temperatura de inversão de fases (método PIT). Cladosporium sp., Fusarium sp. e Penicillium sp. foram os fungos identificados nas amostras de queijo Minas Padrão deteriorados. Tais cepas foram utilizadas na avaliação da atividade antifúngica in vitro e em queijo Minas Padrão do óleo de orégano nanoemulsionado. Nos testes in vitro foram determinadas as concentrações mínimas inibitórias (CMI) do óleo essencial de orégano puro e nanoemulsionado sobre o Cladosporium sp., Fusarium sp. e Penicillium sp. Foram utilizadas fatias de queijo Minas Padrão para avaliar o efeito inibitório das nanoemulsões contendo óleo essencial de orégano. Por último foi avaliado o efeito inibitório das nanoemulsões durante o processo de maturação de queijos Minas Padrão. Determinaram-se valores de CMI para óleo essencial puro de 0,2; 0,3 µg/ml para Fusarium sp. e Penicillium sp., respectivamente. Enquanto para as duas formulações de nanoemulsão; os valores de CMI dependeram da quantidade de óleo essencial de orégano que estava contido nelas...

Produção por método da temperatura de inversão de fases, estudo de estabilidade físico-química, digestabilidade in vitro e citotoxicidade de nanopartículas lipídicas sólidas encapsulando beta-caroteno; Production by phase inversion temperature method, study of physicochemical stability, in vitro digestibility and cytotoxicity of beta-carotene load solid lipid nanoparticle

Gomes, Graziela Veiga de Lara
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/02/2015 PT
Relevância na Pesquisa
66.05%
Nanopartículas lipídicas sólidas (SLN) são sistemas coloidais nanoparticulados muito utilizados para encapsulação de substâncias hidrofóbicas, com o intuito de proteger e aumentar a sua biodisponibilidade. Tais sistemas podem ser produzidos por métodos de baixa energia, como a temperatura de inversão de fase (PIT), a qual é baseada na mudança de solubilidade do tensoativo não iônico polietoxilados com a temperatura. O estudo do comportamento de tais sistemas durante a passagem pelo trato gastrointestinal torna-se interessante, caso deseje-se incorpora-los em matrizes alimentícias. Os modelos in vitro dinâmicos têm sido desenvolvidos para simular mais efetivamente os atributos que ocorrem in vivo, e dentre eles o mais conhecido é o sistema TIM (TNO intestinal model), que simula os principais eventos que ocorrem no lúmen do intestino delgado. Outro parâmetro importante a ser analisado, em nanopartículas passíveis de serem ingeridas, é a citotoxicidade, que pode ser avaliado através do emprego de culturas celulares intestinais e epiteliais. O presente trabalho de doutorado teve como objetivo a utilização de manteiga de cupuaçu e manteiga de murumuru para encapsulação do beta-caroteno em nanopartículas lipídicas sólidas produzidas pelo método PIT...

Preparação e caracterização de micro e nanopartículas lipídicas sólidas para aplicação em cosméticos; Preparation and caracterization of solid lipid micro and nanoparticles, for application in cosmetics

Marcos Roberto Rossan
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2011 PT
Relevância na Pesquisa
46.05%
Neste trabalho, estudou-se o desenvolvimento tecnológico de micro/ nanopartículas lipídicas sólidas para aplicação cosmética capilar. As micropartículas foram produzidas por spray cooling, onde incorporou-se na matriz lipídica, composta por ceras naturais de origem vegetal (cera de carnaúba), mineral (microparafina) e sintética (cera de silicone), um ativo doador de brilho capilar, de nome comercial Activeshine Amazon, composto por uma mistura de triglicerídeos de murumuru e babaçú. As micropartículas foram obtidas a partir de misturas contendo 30% das ceras, porém a incorporação total do ativo na matriz lipídica ocorreu a partir de 70% de cera. A produção das micropartículas foi estudada através de um planejamento estatístico de experimentos e analise de superfície de resposta, onde determinou-se a influência da pressão do ar de atomização e concentração da cera, sobre o diâmetro médio. Os resultados mostraram que a pressão do ar de atomização foi a principal variável de significância estatística para os três tipos de ceras. Foram obtidas micropartículas esféricas, com diâmetro entre 30 - 320 ?m. As nanopartículas foram obtidas a partir da mistura lipídica composta por 50% de Activeshine Amazon e 50% de cera de carnaúba...

Dexamethasone-loaded scaffolds prepared by supercritical assisted phase inversion

Duarte, Ana Rita C.; Mano, J. F.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
Relevância na Pesquisa
66.13%
The aim of this study was to evaluate the possibility of preparing dexamethasone-loaded starch-based porous matrices in a one-step process. Supercritical phase inversion technique was used to prepare composite scaffolds of dexamethasone and a polymeric blend of starch and poly(L-lactic acid) (SPLA) for tissue engineering purposes. Dexamethasone is used in osteogenic media to direct the differentiation of stem cells towards the osteogenic lineage. Samples with different drug concentrations (5–15 wt.% polymer) were prepared at 200 bar and 55 C. The presence of dexamethasone did not affect the porosity or interconnectivity of the polymeric matrices. Water uptake and degradation studies were also performed on SPLA scaffolds. We conclude that SPLA matrices prepared by supercritical phase inversion have a swelling degree of nearly 90% and the material presents a weight loss of 25% after 21 days in solution. Furthermore, in vitro drug release studies were carried out and the results show that a sustained release of dexamethasone was achieved over 21 days. The fitting of the power law to the experimental data demonstrated that drug release is governed by an anomalous transport, i.e., both the drug diffusion and the swelling of the matrix influence the release of dexamethasone out of the scaffold. The kinetic constant was also determined. This study reports the feasibility of using supercritical fluid technology to process in one step a porous matrix loaded with a pharmaceutical agent for tissue engineering purposes.

Towards bioinspired superhydrophobic poly(L-lactic acid) surfaces using phase inversion-based methods

Shi, Jun; Alves, N. M.; Mano, J. F.
Fonte: IOP Publicador: IOP
Tipo: Artigo de Revista Científica
Publicado em //2008 ENG
Relevância na Pesquisa
45.92%
The water repellency and self-cleaning ability of many biological surfaces has inspired many fundamental and practical studies related to the development of synthetic superhydrophobic surfaces. However, the investigation of such substrates made of biodegradable polymers has been scarce. Simple approaches based on a single step, performed at room temperature (and pressure), were implemented to obtain superhydrophobic poly(L-lactic acid) (PLLA) surfaces via phase inversion-based methods, without addition of low-surface-energy compounds. Water contact angles above 150◦ were obtained using some processing conditions. In such cases scanning electronic microscopy micrographs of such surfaces revealed a clear rough texture composed by leafy clusters with micro-nano binary structures. Such materials could be used in specific environmental and biomedical applications, namely in implantable materials or in antibacterial or antithrombogenic surfaces.

Supercritical phase inversion of starch-poly(e-caprolactone) for tissue engineering applications

Duarte, Ana Rita C.; Mano, J. F.; Reis, R. L.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2010 ENG
Relevância na Pesquisa
46.05%
In this work, a starch-based polymer, namely a blend of starch-poly(ε-caprolactone) was processed by supercritical assisted phase inversion process. This processing technique has been proposed for the development of 3D structures with potential applications in tissue engineering applications, as scaffolds. The use of carbon dioxide as non-solvent in the phase inversion process leads to the formation of a porous and interconnected structure, dry and free of any residual solvent. Different processing conditions such as pressure (from 80 up to 150 bar) and temperature (45 and 55°C) were studied and the effect on the morphological features of the scaffolds was evaluated by scanning electron microscopy and micro-computed tomography. The mechanical properties of the SPCL scaffolds prepared were also studied. Additionally, in this work, the in vitro biological performance of the scaffolds was studied. Cell adhesion and morphology, viability and proliferation was assessed and the results suggest that the materials prepared are allow cell attachment and promote cell proliferation having thus potential to be used in some for biomedical applications.

Processing of novel bioactive polymeric matrixes for tissue engineering using supercritical fluid technology

Duarte, Ana Rita C.; Caridade, S. G.; Mano, J. F.; Reis, R. L.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em //2009 ENG
Relevância na Pesquisa
45.92%
The aim of this study was to develop a new process for the production of bioactive 3D scaffolds using a clean and environmentally friendly technology. The possibility of preparing composite scaffolds of Bioglass® and a polymeric blend of starch and poly(L-lactic acid) (SPLA50) was evaluated. Supercritical phase-inversion technique was used to prepare inorganic particles loaded starch-based porous composite matrixes in a onestep process for bone tissue engineering purposes. Due to their osteoconductive properties some glasses and ceramics are interesting materials to be used for bone tissue engineering purposes; however their poor mechanical properties create the need of a polymeric support where the inorganic fraction can be dispersed. Samples impregnated with different concentrations of Bioglass® (10 and 15% wt/wt polymer) were prepared at 200 bar and 55 °C. The presence of Bioglass® did not affect the porosity or interconnectivity of the polymeric matrixes. Dynamic mechanical analysis has proven that the modulus of the SPLA50 scaffolds increases when glass particles are impregnated within the matrix. In vitro bioactivity studies were carried out using simulated body fluid and the results show that a calciumphosphate layer started to be formed after only 1 day of immersion. Chemical analysis of the apatite layer formed on the surface of the scaffold was performed by different techniques...

Superhydrophobic to superhydrophylic biomimetic poly(3-hydroxybutyrate) surfaces made by phase inversion

González-Obeso, Constancio; Song, Wenlong; Rodriguez-Perez, M. A.; Mano, J. F.
Fonte: Trans Tech Publications Publicador: Trans Tech Publications
Tipo: Artigo de Revista Científica
Publicado em //2013 ENG
Relevância na Pesquisa
66.05%
Biodegradable and biocompatible materials have gained increased attentions because of their applications in biomedicine and tissue engineering. Among them, poly(3-hydroxybutyrate) (PHB), a natural origin polymer, has been employed in biomedical applications as a suitable substitute of synthetic polymers for preparing scaffolds and other devices. In this context it is relevant to understand the interactions between the cells and PHB surfaces, which are governed by aspects such as surface topography and chemical composition. Both, surface topography and chemistry determine surface wettability. The aim of this work is to process PHB surfaces exhibiting extreme wettablility properties, ranging from superhydrophobic (surface contact angle higher than 150 degrees) to superhydrophilic (surface contact angle lower than 5 degrees). A simple phase inversion method was used to fabricate surperhydrophobic PHB surface. Chloroform was used as solvent, and a mixture of water and ethanol as the coagulation bath. The water contact angle was found to be 154.3 +/- 2.9 degrees. Furthermore the surface was treated by argon plasma for different times, permitting the control of wettability of the PHB surface from the superhydrophobic to superhydrophilic regime.

Porous Polyimide Membranes Prepared by Wet Phase Inversion for Use in Low Dielectric Applications

Kim, Soohyun; Jang, Keon-Soo; Choi, Hee-Dok; Choi, Seung-Hoon; Kwon, Seong-Ji; Kim, Il-Doo; Lim, Jung Ah; Hong, Jae-Min
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 24/04/2013 EN
Relevância na Pesquisa
46.05%
A wet phase inversion process of polyamic acid (PAA) allowed fabrication of a porous membrane of polyimide (PI) with the combination of a low dielectric constant (1.7) and reasonable mechanical properties (Tensile strain: 8.04%, toughness: 3.4 MJ/m3, tensile stress: 39.17 MPa, and young modulus: 1.13 GPa), with further thermal imidization process of PAA. PAA was simply synthesized from purified pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) in two different reaction solvents such as γ-butyrolactone (GBL) and N-methyl-2-pyrrolidinone (NMP), which produce Mw/PDI of 630,000/1.45 and 280,000/2.0, respectively. The porous PAA membrane was fabricated by the wet phase inversion process based on a solvent/non-solvent system via tailored composition between GBL and NMP. The porosity of PI, indicative of a low electric constant, decreased with increasing concentration of GBL, which was caused by sponge-like formation. However, due to interplay between the low electric constant (structural formation) and the mechanical properties, GBL was employed for further exploration, using toluene and acetone vs. DI-water as a coagulation media. Non-solvents influenced determination of the PAA membrane size and porosity. With this approach, insight into the interplay between dielectric properties and mechanical properties will inform a wide range of potential low-k material applications.

Desenvolvimento de nanopart?culas polim?ricas por polimeriza??o In Situ a partir de nanoemuls?es produzidas por invers?o de fases

Goto, Patr?cia Leme
Fonte: Programa de P?s-Gradua??o em Ci?ncias Farmac?uticas. CIPHARMA, Escola de Farm?cia, Universidade Federal de Ouro Preto. Publicador: Programa de P?s-Gradua??o em Ci?ncias Farmac?uticas. CIPHARMA, Escola de Farm?cia, Universidade Federal de Ouro Preto.
Tipo: Dissertação
PT_BR
Relevância na Pesquisa
46.05%
A produ??o de nanopart?culas polim?ricas (nanoesf?ras e nanoc?psulas) n?o ? novidade no mercado farmac?utico, mas os m?todos de fabrica??o das mesmas variam muito, encontrando-se diferentes t?cnicas de obten??o. Dada a import?ncia das nanopart?culas na otimiza??o da velocidade de ced?ncia e na vetoriza??o de f?rmacos, neste trabalho foi proposto o desenvolvimento de um processo para produ??o de nanoc?psulas polim?ricas, conjugando a t?cnica de polimeriza??o interfacial in situ com a produ??o de nanoemuls?o pelo m?todo de emulsifica??o por invers?o de fases, utilizando mon?meros derivados de ?cido acr?lico, ativadores e iniciadores, e ?leo de origem vegetal (manteiga de murumuru). A nanoemuls?o e a suspens?o de nanoc?psulas foram caracterizadas quanto ao tamanho m?dio de part?cula e o potencial zeta, obtendo part?culas dentro do intervalo de 100 a 200 nm. Testes de estabilidade tamb?m foram realizados para as duas formula??es. A an?lise morfol?gica foi realizada atrav?s de microscopia de for?a at?mica, pela qual se comprovou a forma??o das nanoc?psulas de formato esf?rico. O pol?mero formado ao redor da nanoc?psula foi caracterizado atrav?s de an?lises de espectroscopia por Infravermelho com Transformada de Fourier (FT-IR), apresentando um espectro caracter?stico ao do poli(acrilato de 2-etilhexila); e calorimetria diferencial explorat?ria (DSC)...

Droplet size and stability of nano-emulsions produced by the temperature phase inversion method

Ee, S.; Duan, X.; Liew, C.; Nguyen, Q.
Fonte: Elsevier Science Sa Publicador: Elsevier Science Sa
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
46.05%
We studied the formation and stability of n-decane in water nano-emulsions produced by the phase inversion temperature (PIT) emulsification method using polyoxyethylene lauryl ether as surfactant. The results obtained indicate that the droplet size and size distribution are strongly dependent on the methods of heating and cooling, and on the final temperature to which the mixture is cooled after phase inversion. Importantly, there exists an optimum storage temperature, at which the nano-emulsions are most stable, and develop ultra-small droplet sizes, ranging from 35 nm to 54 nm, with low polydispersity indices (0.2). This optimum temperature is about 20 °C below the PIT, and dependent on the surfactant concentration. Any departure in temperature from the optimum would result in increases in droplet sizes, polydispersity and instability by Ostwald ripening. Furthermore, nano-emulsions destabilized after a long period of storage at different temperatures can be rejuvenated simply by equilibration for a few minutes at the optimum temperature.; Sher Lin Eea, Xiumei Duana, Jeffery Liewa and Q. Dzuy Nguyen; http://www.elsevier.com/wps/find/journaldescription.cws_home/601273/description#description

Effect of electrolytes on the formation and stability of n-dodecane nanoemulsions by the phase inversion temperature (PIT) method.

Liew, Jeffery C.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
Relevância na Pesquisa
66.18%
This research focuses on the effect of sodium chloride (NaCl) or calcium chloride (CaCl₂) on the formation and stability of n-dodecane/non-ionic surfactant/aqueous nanoemulsions produced by the Phase Inversion Temperature (PIT) method. It is because there are only few works done to investigate the effect of electrolyte on the production of nanoemulsions, especially those produced by the PIT method. Furthermore, in this research, the ability for ageing nanoemulsions to reverse their physical properties to freshly-prepared state has also been investigated.. The nanoemulsions were produced by heating aqueous-continuous emulsions (O/W) to oil-continuous (W/O) emulsions, followed by a quenching process to produce O/W nanoemulsions. Pure milliQ water and concentration from 0.001M to 0.1M NaCl or CaCl₂ were used as continuous phase. The non-ionic surfactants used were polyoxyethylene (4) lauryl ether (Brij30) and sorbitan monooleate (S80). The stability was determined by dynamic light scattering technique by measuring the growth of the droplet size and size distribution (PdI) before the nanoemulsions were phase separated, which was determined by visual observation. The reversibility testing was done by measuring the droplet size and PdI as a function of temperatures for a three-day ageing nanoemulsion system. Droplet size as small as 65nm was produced from a brine system while there was 77nm in a pure milliQ water system...

Fabricación y caracterización de membranas poliméricas biocompatibles de poliacrilonitrilo mediante inversión de fases para su aplicación en proliferación y diferenciación de células neuronales; Synthesis and characterization of biocompatible polyacrilonitrile membranes by phase inversion technique for proliferation and differentiation of neural cells

Juveneton, Charlotte
Fonte: Universidade de Cantabria Publicador: Universidade de Cantabria
Tipo: Trabalho de Conclusão de Curso
ENG
Relevância na Pesquisa
46.05%
Grado en Ingeniería Química

Segregation and phase inversion of strongly and weakly fluctuated Brownian particle mixtures in spherical containers

Awazu, Akinori
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/04/2014
Relevância na Pesquisa
45.97%
We investigate the segregation pattern formations of strongly and weakly fluctuated Brownian particle mixtures, which are confined in spherical containers with finite volumes. We consider systems where the container restricts the motions of particles combining two familiar methods: spherically symmetric linear potential and the container edge wall. In such systems, the following two segregation patterns are observed. When the container radius is large enough, more weakly fluctuated particles accumulate around the center of the container than strongly fluctuated particles. On the other hand, inverted distributions of strongly and weakly fluctuated particles are observed when the container radius is small. We also found a similar segregation and phase inversion if such particle mixtures construct a chain (hetero-fluctuated polymer) and are confined in a container with no linear potential. We provide the qualitative mechanism and the relationships for the biopolymer behaviors of such phase inversions.

Formation and stability of nano-emulsions

Tadros, Tharwat F.; Izquierdo, P.; Esquena, Jordi; Solans, Conxita
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 22195 bytes; application/pdf
ENG
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16 pages, 18 figures, 3 tables.-- PMID: 15072948 [PubMed].-- Available online Dec 16, 2003.-- Issue title: "Emulsions, From Fundamentals to Practical Applications" (3rd World Congress on Emulsions, Lyon, France, Sep 2002).; This review describes the principles of formation and stability of nano-emulsions. It starts with an introduction highlighting the main advantages of nano-emulsions over macroemulsions for personal care and cosmetic formulations. It also describes the main problems with lack of progress on nano-emulsions. The second section deals with the mechanism of emulsification and the dynamic light scattering technique for measurement of the droplet size of nano-emulsions. This is followed by a section on methods of emulsification and the role of surfactants. Three methods are described for nano-emulsion preparation, namely high energy emulsification (using homogenisers), low energy emulsification whereby water is added to an oil solution of the surfactant and the principle of the phase inversion temperature (PIT). A section is devoted to steric stabilisation and the role of the adsorbed layer thickness. The problem of Ostwald ripening (which is the main instability process of nano-emulsions) is described in some detail. The methods that can be applied to reduce Ostwald ripening are briefly described. This involves the addition of a second less soluble oil phase such as squalene and/or addition of a strongly adsorbed and water insoluble polymeric surfactant. The last part of the review gives some examples of nano-emulsions that are prepared by the PIT method as well as using high pressure homogeniser. A comparison of the two methods is given and the rate of Ostwald ripening is measured in both cases. The effect of changing the alkyl chain length and branching of the oil was investigated using decane...