The evolution of the reaction conversion and particle size distribution during the microemulsion polymerization of methyl methacrylate (MMA) is used to determine the particle nucleation mechanisms. A pseudo-3-component oil-in-water microemulsion is formed with water, MMA, and a mixture of dodecyltrimethylammonium bromide (DTAB) and diodecyldimethylammonium bromide (DDAB) in a 3:1 weight ratio as surfactant. Polymerization is initiated with either an oil-soluble or a water-soluble initiator and conversion followed either by measurement of the unpolymerized monomer concentration in samples taken during the reaction or by direct on-line densimetry. A two-stage process is observed. The first stage, described by a very slow increase in conversion, is attributed mainly to homogeneous nucleation, and the second stage, characterized by a much higher rate of conversion, involves continuous nucleation and is governed mainly by a micellar-entry mechanism.

This study extends the existing phenomenological thermodynamic model of aqueous microemulsions to nonaqueous microemulsions and examines the phase patterns when the melting temperature of the alkane oil is in the range of other liquid-liquid transition temperatures. The liquid paraffins studied are the alkane oils of greater than 17 carbons and are solid at room temperature. Water, water and ethylene glycol (4∶1 by wt.), propylene glycol and water (4∶1 by wt.), and propylene glycol are the four non-oleic components examined. Homogeneous polyoxyethylene nonionic surfactants and the commercial surfactants of the Brij series, Neodol series, and the LP series were used. Small-angle x-ray scattering gives evidence for the presence of microstructures in these solutions and, thus these systems are true microemulsions at temperatures above the melting point of the alkane. Systematic paths to move from aqueous to nonaqueous microemulsions are outlined. These results are utilized in optimizing the performance requirements of an inkjet printing application.

Spontaneous, single-walled, equilibrium vesicles of controlled size and surface charge can be prepared from aqueous mixtures of simple, commercially available, single-tailed cationic and anionic surfactants. We present detailed phase behavior and structural studies of one such mixture, sodium dodecylbenzenesulfonate (SDBS) and cetyl trimethylammonium tosylate (CTAT) in H2O, as well as results of less complete surveys of other mixtures. The SDBS/CTAT mixture has many features that appear to be common to aqueous mixtures of asymmetric cationic and anionic surfactants. Vesicle formation apparently results from the production of an anion-cation surfactant pair which then acts as a double-tailed zwitterionic surfactant. Although unilamellar vesicles have been created by numerous physical and chemical techniques from multilamellar dispersions, all such vesicle systems revert to the equilibrium, multilamellar phase over time. These catanionic vesicles are stable for periods as long as several years and appear to be the equilibrium form of aggregation.

A novel ink technology has been developed. The fluid vehicle of the ink is a stable, single-phase, water-in-oil (wax) microemulsion at elevated temperatures in the range of 70-degrees-95-degrees-C, yet is a solid at ambient temperatures. This ink, because it is a microemulsion, is stable to freeze-melt cycles. Such an ink is suitable for jetting as a hot melt in conventional continuous or impulse ink jet apparatus. More significantly, it can operate in impulse thermal jet printheads where other hot melt ink-jet ink compositions cannot.

Single-walled, nearly monodisperse, equilibrium vesicles form spontaneously when cholinergics such as choline chloride, acetylcholine chloride, calcium salt of phosphorylcholine chloride, or succinylcholine chloride, a muscle relaxant, are added to the solutions of sodium bis[2-ethylhexyl]sulfosuccinate (AOT). Partial phase diagrams mapping the stable vesicle region are presented for the systems AOT/water/choline chloride, AOT/water/acetylcholine chloride, AOT/water/phosphorylcholine chloride calcium salt, and AOT/water/succinylcholine chloride. The measured diameters for the vesicles made with these choline chloride compounds are 2000A˚for acetylcholine chloride and 1000A˚for choline chloride, succinylcholine chloride, and the calcium salt of phosphorylcholine chloride.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStyrene polymerization in three-component cationic microemulsionsV. H. Perez-Luna, J. E. Puig, V. M. Castano, B. E. Rodriguez, A. K. Murthy, and E. W. KalerCite this: Langmuir 1990, 6, 6, 1040–1044Publication Date (Print):June 1, 1990Publication History Published online1 May 2002Published inissue 1 June 1990https://pubs.acs.org/doi/10.1021/la00096a002https://doi.org/10.1021/la00096a002research-articleACS PublicationsRequest reuse permissionsArticle Views341Altmetric-Citations94LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts

Spontaneous, single-walled, equilibrium vesicles can be prepared from aqueous mixtures of simple, commercially available, single-tailed cationic and anionic surfactants. Vesicle size, surface charge, or permeability can be readily adjusted by varying the ratio of anionic to cationic surfactant. Vesicle formation apparently results from the production of anion-cation surfactant pairs that then act as double-tailed zwitterionic surfactants. These vesicles are quite stable in comparison to conventional vesicles prepared by mechanical disruption of insoluble liquid crystalline dispersions.

Partial phase diagrams showing the domains of existence of a transparent, viscous, lamellar-structured (D)-phase that transforms reversibly into fluid single phase solutions at high temperature are presented for the system: cetyltrimethylammonium bromide (CTAB), two low molecular weight alcohols, and water with and without additives. At constant temperature and with a fixed amount of surfactant, the size and location of this phase in the phase diagram depends upon three composition variables: i) the ratio of concentrations of medium chain alcohol to long chain alcohol (R), ii) the ratio of concentrations of medium chain alcohol to surfactant (R′), and iii) the concentrations of small amounts (up to 10 % by weight) of additives such as ethylene glycol, propylene glycol, and dimethylformamide, as well as NaBr. Small-angle x-ray scattering measurements of these mixtures reveal a lamellar structure. The observed lamellar repeat distances range from 60 A to 290 Å and depend upon the ratiosR andR′ and the concentration of the additives. The mechanical and structural properties of theseD-phases can be tuned by adjustingR andR′. TheD-phase-to-isotropic transition temperature can be varied from near room temperature to above 80 °C by adjustingR andR′.