Featured Research

from universities, journals, and other organizations

Emulsion With A Round-trip Ticket

Date:
June 18, 2007
Source:
John Wiley & Sons, Inc.
Summary:
A British team reports a double inversion of a nanoparticle-containing emulsion: By the successive addition of a surfactant, they were able to convert an oil-in-water emulsion into a water-in-oil emulsion, and then back again.

Oil and water are not miscible. However, it is possible to combine both into an emulsion in which they act as a unit—for example, in creams, body lotion, milk, or mayonnaise. In these substances, one of the two liquids is dispersed as tiny droplets in the other, which requires an emulsifier and vigorous shaking or stirring.

Whether the oil droplets are suspended in water (oil-in-water emulsion O/W) or the water droplets are suspended in oil (water-in-oil emulsion W/O) depends on various factors. In the journal Angewandte Chemie, a British team from the University of Hull now reports a double inversion of a nanoparticle-containing emulsion: By the successive addition of a surfactant, they were able to convert an O/W emulsion into a W/O emulsion and then back again.

The emulsifier’s job is to make droplet formation easier and to counteract separation. In addition to surfactants (substances contained in detergents and the like), fine solid particles also have a stabilizing effect. Mustard powder has thus long been used to stabilize mayonnaise. Both surfactants and particles aggregate at the phase boundary of the two liquids and keep the droplets from flowing together. Many commercial formulations contain surfactants as well as solid particles.

If the conditions are changed, a phase inversion can occur, converting an O/W into a W/O emulsion, for example, if more and more surfactant is added. This is no great feat. However, Bernard P. Binks and Johnny A. Rodrigues have now achieved something astonishing: a double inversion. Their system initially contains silica nanoparticles and a small quantity of a surfactant with a water-loving (hydrophilic), positively charged head and two nonpolar, water-repellent (hydrophobic) tails.

The tiny silica spheres are negatively charged, hydrophilic, and easily wettable by water. In this state, they stabilize oil drops in water (O/W). If more surfactant is added, a layer of surfactant molecules surrounds each sphere, all with their hydrophobic tails sticking out. The spheres are now covered with a hydrophobic layer and are no longer wettable. They stop repelling each other and begin to aggregate.

This causes the emulsion to undergo its first inversion into W/O. If further surfactant is then added, these additional molecules lodge tail-to-tail with those already surrounding the spheres. This forms a double layer around the spheres, with the positively charged heads of the second surfactant layer now sticking out. The spheres thus once again have a charged, hydrophilic surface and again stabilize oil droplets in water. The emulsion undergoes its second inversion back into O/W.


Story Source:

The above story is based on materials provided by John Wiley & Sons, Inc.. Note: Materials may be edited for content and length.


Cite This Page:

John Wiley & Sons, Inc.. "Emulsion With A Round-trip Ticket." ScienceDaily. ScienceDaily, 18 June 2007. <www.sciencedaily.com/releases/2007/06/070614114147.htm>.
John Wiley & Sons, Inc.. (2007, June 18). Emulsion With A Round-trip Ticket. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2007/06/070614114147.htm
John Wiley & Sons, Inc.. "Emulsion With A Round-trip Ticket." ScienceDaily. www.sciencedaily.com/releases/2007/06/070614114147.htm (accessed September 19, 2014).

Share This



More Matter & Energy News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Newsy (Sep. 18, 2014) Apple's new operating system, iOS 8, comes with Apple's killswitch feature already activated, unlike all the models before it. Video provided by Newsy
Powered by NewsLook.com
Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
Powered by NewsLook.com
Space Race Pits Bezos Vs Musk

Space Race Pits Bezos Vs Musk

Reuters - Business Video Online (Sep. 16, 2014) Amazon CEO Jeff Bezos' startup will team up with Boeing and Lockheed to develop rocket engines as Elon Musk races to have his rockets certified. Fred Katayama reports. Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins