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Mixed Systems of Hydrophobically Modified Polyelectrolytes: Controlling Rheology by Charge and Hydrophobe Stoichiometry and Interaction Strength

Antunes, Filipe E.; Lindman, Björn; Miguel, Maria G.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
ENG
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Rheology and phase separation were investigated for aqueous mixtures of two oppositely charged hydrophobically modified polyelectrolytes. The typical phase separation, normally seen for oppositely charged polymer mixtures, is dramatically reduced by the presence of hydrophobic modification, and phase separation is only detected close to the point of charge neutralization. While the two polyelectrolytes separately can give high viscosities and a gel-like behavior, a pronounced maximum in viscosity and storage modulus with the mixing ratio of the polyelectrolytes is observed; the maximum is located between the points of charge and hydrophobe stoichiometry and reflects a combination of hydrophobic and electrostatic association. Lowering the charge density of the anionic polymer leads to a strengthened association at first, but at lower charge densities there is a weakened association due to the onset of phase separation. The strength of the electrostatic interaction was modified by adding salt. Increased ionic strength can lead to phase separation and to increased or decreased viscosity depending on the polyelectrolyte mixing ratio.; http://dx.doi.org/10.1021/la050590k

Aggregation behavior of hydrophobically modified dextran in aqueous solution: a fluorescence probe study

Vieira, NAB; Moscardini, M. S.; Tiera, VAD; Tiera, M. J.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 137-143
ENG
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Dextrans (M-W = 11.000 and M-w = 40.000) have been modified with 4-hexyl benzoyl chloride and their aggregation behavior was studied in aqueous solution employing the fluorescent probes pyrene and 1,8 anilinonaphtalene sulfonic acid sodium salt (1,8 ANS). The photophysical studies showed that above a critical concentration the derivatives tend to form aggregates having different properties, which depend on both the degree of substitution (alpha) and the molecular weight of the sample. The parameter alpha has a marked effect on the critical aggregation concentrations (CAC) and aggregate proper-ties. Hydrophobic microenvironments can be detected for substituted dextrans having alpha values varying from 0.01 to 0.19. CAC values decreased by two orders and magnitude when the molecular weight increased from 11 to 40 kDa, leading to formation of more apolar aggregates and diminishing by about 30% the polarity of the microenviromnents. Pre-aggregation was evidenced by pyrene excimer emission and intermolecular interactions were responsible by the formation of aggregates leading to solution behaviour similar to that of common surfactants. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Aggregation behaviour of hydrophobically modified poly(allylammonium) chloride

Tiera, M. J.; Tiera, VAD; de Toledo, E. C.; de Sena, G. L.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 1052-1060
ENG
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The behaviour of hydrophobically modified poly(allylammonium) chloride having octyl, decyl, dodecyl and hexadecyl side chains has been studied in aqueous solution using fluorescence emission techniques. Micropolarity studies using the I-1/I-3 ratio of the vibronic bands of pyrene show that the formation of hydrophobic microdomains depends on both the length of the side chain and the polymer concentration. The I-1/I-3 ratio of the polymers with low hydrophobe content (less than 5% mel) changes substantially when reaching a certain concentration. These changes are assigned to aggregation originating from interchain interactions. This behaviour is also confirmed by the behaviour of the monomer/excimer emission intensities of pyrene- dodecanoic acid used as a probe. For polymers having dodecyl side chains and hydrophobe contents higher than 10%, aggregates are formed independently of the polymer concentration. Anisotropy measurements show that microdomains resulting from the inter- and/or intramolecular interactions are similar to those observed for cationic surfactants. Viscosity measurements show that the coil dimensions are substantially decreased for the polymers having high hydrophobe contents, indicating intramolecular associations.

Dispersed lipid liquid crystalline phases stabilized by a hydrophobically modified cellulose

Almgren, Mats; Borné, Johanna; Feitosa, Eloi; Khan, Ali; Lindman, Björn
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 2768-2777
ENG
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Aqueous dispersions of monoolein (MO) with a commercial hydrophobically modified ethyl hydroxyethyl cellulose ether (HMEHEC) have been investigated with respect to the morphologies of the liquid crystalline nanoparticles. Only very low proportions of HMEHEC are accepted in the cubic and lamellar phases of the monoolein-water system. Due to the broad variation of composition and size of the commercial polymer, no other single-phase regions were found in the quasi-ternary system. Interactions of MO with different fractions of the HMEHEC sample induced the formation of lamellar and reversed hexagonal phases, identified from SAXD, polarization microscopy, and cryogenic TEM examinations. In excess water (more than 90 wt %) coarse dispersions are formed more or less spontaneously, containing particles of cubic phase from a size visible by the naked eye to small particles observed by cryoTEM. At high polymer/MO ratios, vesicles were frequently observed, often oligo-lamellar with inter-lamellar connections. After homogenization of the coarse dispersions in a microfluidizer, the large particles disappeared, apparently replaced by smaller cubic particles, often with vesicular attachments on the surfaces, and by vesicles or vesicular particles with a disordered interior. At the largest polymer contents no proper cubic particles were found directly after homogenization but mainly single-walled defected vesicles with a peculiar edgy appearance. During storage for 2 weeks...

Toxicidade de nanomateriais de ácidos poliacrílicos hidrofobicamente modificados; Toxicity of hydrophobically modified polyacrylic acid nanomaterials

Tavares, Jorge Abel dos Santos Silva
Fonte: Universidade de Aveiro Publicador: Universidade de Aveiro
Tipo: Dissertação de Mestrado
POR
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A crescente demanda por novos e melhores produtos levou a um desenvolvimento exponencial de novos nanomaterials (NM) manufacturados desde a década de 90. A corrente massificação de NM em produtos de uso quotidiano promove o contacto entre NM e o ambiente com possíveis efeitos adversos para os ecossistemas. O trabalho apresentado pretende sugerir qual o NM de ácido poliacrílico hidrofobicamente modificado (HMPAA) menos prejudicial para o ambiente de entre seis HMPAA NM, dos quais um (HMPAA5) é atualmente comercializado, com o intuito de contribuir para a agenda da União Europeia em Nanosegurança: Inovações em nanotecnologia e nanomaterials sustentáveis e seguros. As seis variações de NMs HMPAA foram obtidos através da modificação de conformações reticuladas e inserção de grupos hidrofóbicos em diferentes posições do NM. Cada variação de suspensões HMPAA foi caracterizada através da utilização de técnicas de espalhamento dinâmico de luz e medidos os valores de condutividade e pH. A caracterização ecotoxicológica dos seis NMs foi feita recorrendo a uma bateria de ensaios padrão, letais e sub-letais, com espécies de diferentes grupos taxonómicos e funcionais, com o objetivo de aferir diversos graus de sensibilidade: (i) Vibrio fisheri...

Solution properties of a hydrophobically associating polyacrylamide and its polyelectrolyte derivatives determined by light scattering, small angle x-ray scattering and viscometry

Maia,Ana M. S; Villetti,Marcos A; Vidal,Rosangela R. L; Borsali,Redouane; Balaban,Rosangela C
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2011 EN
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A hydrophobically-modified polyacrylamide and two partially hydrolyzed derivatives containing hydrophobic and carboxylic groups were prepared by micellar polymerization and post-hydrolysis. The molecular weight, second virial coefficient and radius of gyration were determined by static light scattering (SLS). Dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) were employed to determine the aggregate formation and type of chain packing in the semidilute regime, respectively. The behavior of solutions in dilute and semidilute regimes was also studied by viscometry and rheology. The hydrophobically-modified polyacrylamide showed a tendency to form aggregates due to the hydrophobic groups, but not enough to increase apparent viscosity. The partially hydrolyzed derivatives did not show the same aggregate-forming tendency. Rather, they exhibited anisotropic behavior, due to the charge density introduced into the polymer chain, which led to a more elongated macromolecular conformation and higher viscosity.

Hydrophobically Modified Polyacrylamide Block Copolymers for Fast, High-Resolution DNA Sequencing in Microfluidic Chips

Forster, Ryan E.; Chiesl, Thomas N.; Fredlake, Christopher P.; White, Corin V.; Barron, Annelise E.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /12/2008 EN
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By using a microfluidic electrophoresis platform to perform DNA sequencing, genomic information can be obtained more quickly and affordably than the currently employed capillary array electrophoresis (CAE) instruments. Previous research in our group has shown that physically cross-linked, hydrophobically modified polyacrylamide (HMPAM) matrices separate double-stranded DNA (dsDNA) more effectively than linear polyacrylamide (LPA) solutions. Expanding upon this work, we have synthesized a series of linear polyacrylamide-co-dihexylacrylamide (LPA-co-DHA) block copolymers specifically designed to electrophoretically sequence single-stranded DNA (ssDNA) quickly and efficiently on a microfluidic device. By incorporating very small amounts of N,N-dihexylacrylamide, a hydrophobic monomer, these copolymer solutions achieved up to ~10% increases in average DNA sequencing read length over LPA homopolymer solutions of matched molar mass. Additionally, the inclusion of the small amount of hydrophobe does not significantly increase the polymer solution viscosities, relative to LPA solutions, so that channel loading times between the copolymers and the homopolymers are similar. The resulting polymer solutions are capable of providing enhanced sequencing separations in a short period of time without compromising the ability to rapidly load and unload the matrix from a microfluidic device.

Surfactants modify the release from tablets made of hydrophobically modified poly (acrylic acid)☆

Knöös, Patrik; Onder, Sebla; Pedersen, Lina; Piculell, Lennart; Ulvenlund, Stefan; Wahlgren, Marie
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 13/09/2013 EN
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Many novel pharmaceutically active substances are characterized by a high hydrophobicity and a low water solubility, which present challenges for their delivery as drugs. Tablets made from cross-linked hydrophobically modified poly (acrylic acid) (CLHMPAA), commercially available as Pemulen™, have previously shown promising abilities to control the release of hydrophobic model substances. This study further investigates the possibility to use CLHMPAA in tablet formulations using ibuprofen as a model substance. Furthermore, surfactants were added to the dissolution medium in order to simulate the presence of bile salts in the intestine.

Enhanced Bonding Strength of Hydrophobically Modified Gelatin Films on Wet Blood Vessels

Yoshizawa, Keiko; Taguchi, Tetsushi
Fonte: Molecular Diversity Preservation International (MDPI) Publicador: Molecular Diversity Preservation International (MDPI)
Tipo: Artigo de Revista Científica
Publicado em 29/01/2014 EN
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The bonding behavior between hydrophobically modified alkaline-treated gelatin (hm-AlGltn) films and porcine blood vessels was evaluated under wet conditions. Hexanoyl (Hx: C6), decanoyl (Dec: C10), and stearyl (Ste: C18) chlorides were introduced into the amino groups of AlGltn to obtain HxAlGltn, DecAlGltn, and SteAlGltn, respectively, with various modification percentages. The hm-AlGltn was fabricated into films and thermally crosslinked to obtain water-insoluble films (t-hm-AlGltn). The 42% modified t-HxAlGltn (t-42HxAlGltn) possessed higher wettability than the 38% modified t-DecAlGltn (t-38DecAlGltn) and the 44% modified t-SteAlGltn (t-44SteAlGltn) films, and the t-42HxAlGltn film showed a high bonding strength with the blood vessel compared with all the hm-AlGltn films. Histological observations indicated that t-42HxAlGltn and t-38DecAlGltn remained on the blood vessel even after the bonding strength measurements. From cell culture experiments, the t-42HxAlGltn films showed significant cell adhesion compared to other films. These findings indicate that the Hx group easily interpenetrated the surface of blood vessels and effectively enhanced the bonding strength between the films and the tissue.

Dynamic light scattering of semidilute hydrophobically modified alkali-soluble emulsion solutions with different lengths of poly(ethylene oxide) spacer chain

Dai, S.; Tam, K.; Jenkins, R.
Fonte: John Wiley & Sons Inc Publicador: John Wiley & Sons Inc
Tipo: Artigo de Revista Científica
Publicado em //2005 EN
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Semidilute solutions of hydrophobically modified alkali-soluble emulsion (HASE) were examined by dynamic light scattering and rheological techniques. For the model polymer without associative macromonomer, two q2 dependent diffusional modes were detected in the decay time distributions. With increasing hydrophobicity of the associative macromonomer, the narrow fast peak was substituted by a shallow broad peak and only one q2 dependent slow mode could be accurately detected, which indicated that the heterogeneity of these associated clusters increases with increasing carbon number. The bulk steady-shear viscosity exhibits similar results to the diffusion coefficients of the aggregate observed from light scattering measurements. The length of poly(ethylene oxide) (PEO) spacer chain alters the solution properties as well as the associative cluster structure. With increasing length of PEO spacer chain, intramolecular association was substituted by intermolecular association. For EO segment larger than 32 units, intramolecular association dominates, where the formation of HASE aggregates is controlled by the balance of electrostatic repulsion and hydrophobic attraction.; Sheng Dai, Kam Chiu Tam and Richard D. Jenkins

The capture and stabilization of curcumin using hydrophobically modified polyacrylate aggregates and hydrogels

Harada, T.; Pham, D.T.; Lincoln, S.F.; Kee, T.W.
Fonte: ACS Publications Publicador: ACS Publications
Tipo: Artigo de Revista Científica
Publicado em //2014 ENG
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Hydrophobically modified polyacrylates are shown to suppress the degradation of the medicinal pigment curcumin under physiological conditions. In aqueous solution, the 3% octadecyl randomly substituted polyacrylate, PAAC18, forms micelle-like aggregates at a concentration of <1 wt % and a hydrogel at >1 wt %. Under both conditions, PAAC18 shows a remarkable ability to suppress the degradation of curcumin at pH 7.4 and 37 °C such that its degradation half-life is increased by 1600-2000-fold. The suppression of degradation is attributed to hydrophobic interactions between curcumin and the octadecyl substituents of PAAC18 within the micelle-like aggregates and the hydrogel, as indicated by 2D NOESY 1H NMR spectroscopy. UV- visible absorption titration results are consistent with the interaction of curcumin with five octadecyl substituents on average, which appears to substantially exclude water and greatly decrease the curcumin degradation rate. Dynamic light scattering and zeta potential measurements show the average hydrodynamic diameters of the PAAC18 aggregates to be 0.86-1.15 micrometers with a negative surface charge. In contrast to the octadecyl substitution, the 3% dodecyl randomly substituted polyacrylate, PAAC12, shows a negligible effect on slowing the degradation of curcumin...

Estudo reológico e calorimétrico de micelas como reticulantes transientes de celuloses hidrofobicamente modificadas; Rheological and calorimetric study of micelles as transients cross-links of hydrophobically modified celluloses

Eduardo José Creatto
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 24/02/2015 PT
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A química supramolecular envolve estruturas mantidas por interações intermoleculares. Neste contexto, sistemas que apresentam estruturas auto organizadas são de interesse devido importância como ciência de base bem como aplicabilidade. Neste trabalho foram utilizadas micelas de brometo de hexadeciltrimetilamônio (CTAB) como reticulantes de hidroxietilceluloses hidrofobicamente modificadas. Como as micelas estão em constante quebra e recombinação, reticulações transientes são obtidas. Tais sistemas apresentam comportamento reológico característico, dependente da concentração do surfactante. Obervou-se que a celulose que apresenta maior ramificação hidrofóbica resulta em aumento mais efetivo da viscosidade como consequência do maior grau de reticulação. A Técnica de calorimetria de titulação isotérmica (ITC) foi utilizada de modo a compreender os processos energéticos envolvidos na agregação. Com esta pôde-se obter parâmetros do sistema como cmc, cac e ?H°mic . Elucidou-se também que as interações polímero-surfactante são de origem hidrofóbica. A adição de salicilato de sódio (NaSal) em solução de CTAB leva a formação de micelas gigantes. Determinou-se por ITC a razão, [CTAB]/[NaSal], em que ocorre a formação de micelas gigantes...

How does a non-ionic hydrophobically modified telechelic polymer interact with a non-ionic vesicle? Rheological aspects

Santos, Tiago dos; Medronho, Bruno; Antunes, Filipe E.; Lindman, Björn; Miguel, Maria
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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The association between hydrophobically modified polyethylene glycol, HM-PEG, and non-ionic vesicles of tetraethylene glycol monododecyl ether, C12E4, was investigated. HM-PEG is in a triblock form, with an alkyl chain attached to each hydrophilic polymer-end. Such polymer structure is denoted as telechelic. The vesicle average radius was measured by self-diffusion measurements. The system exhibits both a monophasic gel and biphasic regions. The monophasic region was characterized from a rheological point of view. We argue that the gel formation is due to the presence of polymer crosslinks between different surfactant aggregates, once the polymer's hydrophobic moieties may adsorb into the vesicle bilayer. This association is strongly concentration dependent which is reflected in the monotonic increase of the storage modulus, relaxation time and shear viscosity with the addition of surfactant and/or polymer.; http://www.sciencedirect.com/science/article/B6TFR-4NCJCK1-5/1/aef7c974b8674e6ae872e17798c00d3d

A rheological investigation of the association between a non-ionic microemulsion and hydrophobically modified PEG. Influence of polymer architecture

Antunes, Filipe E.; Thuresson, Krister; Lindman, Björn; Miguel, Maria G.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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Hydrophobically modified polymers (HM-P) typically behave as thickeners in a wide range of systems. The thickening effect in an aqueous solution of this kind of polymer depends on intermolecular hydrophobic associations and also on chain entanglements if the polymer concentration is significantly above the overlap concentration. In the present investigation a rather short end-capped polymer has been investigated at concentrations that are significantly below the overlap concentration. Despite the rather low polymer concentration, polymer chains were connected into a three-dimensional network by using microemulsion droplets as cross-linking points. The simple structure of the solution simplifies interpretations of results since chain entanglements can be expected to be of low importance and only intermolecular hydrophobic associations have to be considered. In particular the rheological response is in most cases well characterized by one single relaxation time and, then, the solution can be rationalized within the framework of the Maxwell model. We have found that the length of the polymer chain's hydrophobic end-groups, as well as the temperature, have a large influence on dynamics of the system, while the length of the hydrophilic mid-block has a relatively small significance. On the other hand...

Self-aggregation of hydrophobically modified dextrin and their interaction with surfactant

Bai, Guangyue; Gonçalves, Catarina; Gama, F. M.; Bastos, Margarida
Fonte: Elsevier B.V Publicador: Elsevier B.V
Tipo: Artigo de Revista Científica
Publicado em /01/2008 ENG
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A series of newly hydrophobically modified polymers (dexC16) with different degrees of substitution (DSC16) have been synthesized. They can self-assemble to form micelle-like aggregates through association of the hydrophobic alkyl chains in aqueous solution. The self-aggregation processes, i.e. the critical micelle concentrations (cmc's) of the polymers were characterized by steady-state fluorescence. Further, the interaction between these dexC16 polymers and ionic surfactants (SOS, SDS and DTAC) was investigated by isothermal titration calorimetry (ITC). For the studied mixed systems some important parameters can be derived from calorimetric titration curves, such as interaction enthalpies, critical concentrations and enthalpies of aggregation. The critical concentrations and the aggregation behaviour for the dexC16/SDS system were confirmed by fluorescence measurements. The effects of hydrophobic side group concentrations on the interaction were evaluated in detail. Importantly, we show that the aggregation behaviour of the mixed systems depends on the molar ratio of surfactant to hydrophobic side group (R = ns/nside group).; Fundação para a Ciência e a Tecnologia (FCT)

Guanabenz (Wytensin™) selectively enhances uptake and efficacy of hydrophobically modified siRNAs

Osborn, Maire F.; Alterman, Julia F.; Nikan, Mehran; Cao, Hong; Didiot, Marie C.; Hassler, Matthew R.; Coles, Andrew H.; Khvorova, Anastasia
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
EN
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One of the major obstacles to the pharmaceutical success of oligonucleotide therapeutics (ONTs) is efficient delivery from the point of injection to the intracellular setting where functional gene silencing occurs. In particular, a significant fraction of internalized ONTs are nonproductively sequestered in endo-lysosomal compartments. Here, we describe a two-step, robust assay for high-throughput de novo detection of small bioactive molecules that enhance cellular uptake, endosomal escape, and efficacy of ONTs. Using this assay, we screened the LOPAC (Sigma–Aldrich) Library of Pharmacologically Active Compounds and discovered that Guanabenz acetate (Wytensin™), an FDA-approved drug formerly used as an antihypertensive agent, is capable of markedly increasing the cellular internalization and target mRNA silencing of hydrophobically modified siRNAs (hsiRNAs), yielding a ∼100-fold decrease in hsiRNA IC50 (from 132 nM to 2.4 nM). This is one of the first descriptions of a high-throughput small-molecule screen to identify novel chemistries that specifically enhance siRNA intracellular efficacy, and can be applied toward expansion of the chemical diversity of ONTs.

Poly(ethylene oxide)s hydrophobically modified. Adsorption and spreading at the air-water interface

Urzúa, Marcela; Gargallo, Ligia; Radic, Deodato; Leiva, Angel
Fonte: ACADEMIC PRESS INC ELSEVIER SCIENCE Publicador: ACADEMIC PRESS INC ELSEVIER SCIENCE
Tipo: Artículo de revista
EN
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A comparative study of spread and adsorbed monolayer of poly(ethylene oxide)s of different molecular weight hydrophobically modified with alkyl isocyanates of different length chain is reported. The modification of the polymer was carried out according to reported procedures. The polymers obtained were studied at the air-water interface by Langmuir isotherms for spread monolayers and by Gibbs isotherms for the adsorption process. Isotherms obtained are interpreted in terms of the hydrophobic and hydrophilic balance of the polymers. Limiting area per repeating unit (A(0)) and collapse pressure (pi(c)) from spread monolayers were obtained. Spread monolayers of the hydrophobically modified polymers show larger collapse pressure values than unmodified polymer monolayers. In the adsorption process the excess surface concentration Gamma(infinity), area per repeat unit sigma, and efficiency of the adsorption were determined. The values of the area occupied per repeat unit in adsorbed monolayer (sigma) were larger than those of the spread monolayer. The efficiency of the adsorption of poly(ethylene oxide)s increases with the hydrophobic modification and with the alkyl chain length.

Swollen Micelles Plus Hydrophobically Modified Hydrosoluble Polymers in Aqueous Solutions: Decoration Versus Bridging. a Small Angle Neutron Scattering Study

Filali, Mohammed; Aznar, Raymond; Svenson, Mattias; Porte, Gregoire; Appell, Jacqueline
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/10/2004
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In this paper we examine the effective interactions introduced between the droplets of an oil in water microemulsion upon progressive addition of hydrophobically modified water soluble poly(ethylene oxide)-PEO using essentially small angle neutron scattering. To discuss the relative importance of decoration and bridging of the droplets we compare analogous samples with addition of a PEO grafted at both extremities with hydrophobic C12H 25 chains (PEO-2m) or addition of a PEO grafted at one extremity only with a C12H 25 chain (PEO-m). PEO-m or PEO-2m adsorb onto the droplets via their hydrophobic extremities and the droplets are found to retain their form and size upon addition of up to 40 hydrophobic C12H 25 chains per droplet. When the volume fraction of droplets is less than about 10%, the effective interactions introduced by PEO-m or PEO-2m are found to be very different: PEO-m introduces a repulsive interaction while PEO-2m introduces an effective attractive interaction. This attractive interaction leads to an associative phase separation in the range of low volume fraction when a sufficient amount of PEO-2m is added.

Synthesis and study of molecular interactions between phosphatidyl choline and two laminin derived peptides hydrophobically modified

Alsina, M. Asunción; Ortiz, A.; Polo, D.; Comelles, Francesc; Reig Isart, Francesca
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 19968 bytes; application/msword
ENG
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6 pages, 3 tables, 5 figures.; Two peptides based on the active SIKVAV sequence were synthesized and hydrophobically modified through attachment of a myristoyl residue to the amino terminal group. A comparative study was carried out on the physicochemical properties of both parent and hydrophobically modified structures. Properties studied were hydrophobicity, surface activity, spreadability on aqueous surfaces, penetration in lipid monolayers, aggregation and haemolytic activity. Results obtained indicate that myristoyl containing peptides form micelles at 10−6 M concentration, whereas parent peptides start to aggregate at 10−5 M. All of them are able to spread on aqueous surfaces forming stable monolayers. Concerning their haemolytic activity only one of the sequences promotes a partial lysis of erythrocytes after 30 min incubation at 37 °C and 10−5 M concentration in the media; The technical asistence of Mary Osuna is gratefully acknowledged. This work was carried out with financial help from Lipotec S.A.; Peer reviewed

Influence of Hydrophobe, Surfactant and Salt Concentrations in Hydrophobically Modified Alkali-Soluble Polymers Obtained by Solution Polymerization

Jiménez Regalado,Enrique Javier; Rivera Vallejo,Claudia Cecilia; Maldonado Textle,Hortensia; Guerrero,Ramiro; Espinosa Muñoz,Jorge Félix
Fonte: Sociedad Química de México A.C. Publicador: Sociedad Química de México A.C.
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2012 EN
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The viscosity of hydrophobically modified alkali-soluble polymers to different hydrophobic macromonomer concentrations in the presence of various concentrations of anionic surfactant and salt were investigated. Associative polymers containing both ionic sites and small number of hydrophobic groups were prepared, and their thickening properties in aqueous solution were investigated. Solution polymerization was used for obtained the different polymers. Relationships between hydrophobe, sodium dodecyl sulfate (SDS) and salt (NaCl) concentrations are proposed. Owing to the competition between attractive hydrophobic interaction and repulsive electrostatic interactions, such hydrophobically modified polymers exhibit various rheological behaviors in aqueous solution depending on hydrophobic macromonomer, SDS and NaCl concentrations.