Colloids and Emulsions

Colloids and Emulsions
By Jonathan Collins, Ha Dihn,
Heather Gonzales, Ursula Koniges,
and Andrew Nordmeier
Chemical Engineering 498A
Spring 2007

Introduction
Colloids and emulsions are important topics with respect to the developing fields of
nanotechnology and nanoscience. This report provides an introduction to each of these subjects;
information is presented regarding the function and history of each topic, as well as current
applications, and research into the potential future applications of each.
Colloids
Definition and History
What is a colloid? According to the Merriam-Webster dictionary, a colloid is “a substance that
consists of particles dispersed throughout another substance which are too small for resolution with an
ordinary light microscope but are incapable of passing through a semi permeable membrane”. In other
words, a colloid is a heterogeneous mixture composed of two or more particles whose sizes range
within 1 to 1000 nanometers in diameter. Such particles are small enough to completely mix without
any variation throughout the mixture, but differ from molecules in that it cannot be separated by any
type of filtration or gravity. A few examples of colloids are smoke, fog, and glues.
Association colloids are a class of colloids which are amphiphilic (meaning they have hydrophilic and
hydrophobic ends). Like molecular colloids, association colloids are composed of monomers. However,
the monomers of association colloids self-aggregate in solution to form micelles. These micelles form
through van der Waals, and/or hydrogen bonding. A common example of an association colloid is a soap
and water mixture. Biological examples of association colloids include (in solution) bile salts, and fatty
acids. ( P. Garidel and A. Hildebrand, 2005)
Colloids were discovered and named by Thomas Graham in 1849 through his work with crystalloids
(particles capable of creating true solutions with the added ability of being crystallized). This came
about as he took a solution of sugar and glue enclosed in a semi permeable material and passed this
through a stream of running water. He later found that the sugar had separated and joined the running
water stream whereas the glue did and could not. With continued study on the matter through 1861,
he quickly became the “father of colloid science”.
Graham’s experimentation and research was later supported and confirmed by two independent
groups of scientist, Boris Deryagin and Lev Landau in Russia and Evert Verwey and Theo Overbeek in
Holland. They determined that the stability of colloids was a result of a balance between the attractive
and repulsive forces within the mixture, which causes the key difference between a colloid and a
crystalloid. This theory later became known as the Deryagin-Landau-Verwey-Overbeek theory, or the
“DLVO”, and increased further interest in the study of colloidal chemistry.

Current Research
Colloids are a part of everyday life. Paints, detergents, soap, even butter, are examples of colloids.
However, as varied and interesting as the use of colloids today is, the use of colloids tomorrow is much
more fascinating. Many scientists are working to build tomorrow today, to borrow a phrase, and
researching many things with colloids, from dirt to space.
One such researcher is George Redden. Redden is a man who studies dirt, and things that
contaminate dirt. Many scientists think that colloids are the reason that contaminants travel much
farther than they are expected to. Redden flipped that reasoning on its head; if colloids can take
contaminants away from a site, then, by the same token, they can bring beneficial molecules in.
Redden's research is focused on how colloids work, so that he can eventually fabricate colloids that act
as miniature transports (http://www.eurekalert.org/features/doe/2002-01/dne-ds053102.php).
Not only could colloids be used to heal the planet, but also the human body. Currently, some
research is being done regarding the use of association colloids in drug delivery systems. ( P. Garidel and
A. Hildebrand, 2005) Another example of a developing application of colloids for human health is the
use of colloidal silver (usually silver attached to a protein and suspended in water) to help fight diseases.
Research suggests that colloidal silver may be a powerful antibiotic. It works by disabling the enzyme
that certain bacteria, fungi, and viruses use for oxygen metabolism. This enzyme, however, is not found
in humans, meaning that colloidal silver would only interfere with foreign invaders. As such, it appears
to be both safe and effective, with little to no side effects (http://www.all-natural.com/silver-1.html).
Even NASA has started experimenting with colloids. NASA is currently growing colloids in space, and
studying what happens. They hope that the unique properties of space will give insight into colloidal
manufacturing and engineering. If this is the case, this knowledge could then be applied to create new
colloids with distinct properties for things like semiconductors or electro-optics
(http://www.nasa.gov/centers/glenn/about/fs12grc.html).
From the vastness of space to the mysteries of the human body, colloids seem to be involved with
just about everything. Many scientists are doing research on just that: everything. Paul Chaikin and Bill
Russell, for instance, are two scientists who are researching colloids to research things even smaller.
Colloids are in that fuzzy area between "micro" and "macro" -scopic. However, they're big enough to
see with microscopes, but small enough to accurately model the way atoms move around and interact.
As such, the study of colloids is facilitating the study of matter at its most basic level. Since the atomic
properties of matter determine all of its physical properties, Chaikin and Russell's research could
eventually lead to engineering, on a colloidal scale, of materials whose properties could be made to
order: this much heat capacity or that much electrical conductivity
(http://exploration.nasa.gov/articles/physicalsciences_06-2002_lite.html).

Emulsions
Definition and History
Emulsions are mixtures of two immiscible liquids; they can be categorized as colloids in which both
the dispersed phase and the dispersion medium are liquids. Some examples of familiar emulsions are
butter, espresso, and mayonnaise. Because a large number of emulsions contain water as one of the
two phases, emulsions are classified into two categories: 1) oil-in-water and 2) water-in-oil. Oil-in-water
emulsions consist a dispersed phase of oil droplets in a water medium. Water-in-oil emulsions consist of
a dispersed phase of oil in a water medium. One can distinguish between an emulsion types based on
the volume fraction of the two phases.
Emulsions are very unstable, so they do not form spontaneously. In an emulsion, there must be
a catalyst called an “emulsifying agent” or an “emulsifier” to stabilize the dispersed medium. The
emulsifying agent decreases the interfacial tension between the two phases. Whichever phase the
emulsifiers or emulsifying particles are better able to dissolve in is the dispersed phase.
A large number of emulsifiers are known to science. Egg yolk proteins are familiar emulsifying agents;
their stabilizing properties can be observed in common food items such as mayonnaise and salad
dressings. Emulsions can be prepared by shaking together two immiscible liquids or adding one phase
drop by drop to the other phase with some form of agitation. In industry, emulsifying machines process
emulsification.
One important application of emulsions is emulsion polymerization. This field originated with the
development of synthetic rubber. Early emulsion polymerization research during the first half of the
twentieth century focused around the development of synthetic rubber. This early research led to the
development of products such as plastics, and polymer dispersions (e.g. latex/acrylic paints).
Current Research
The process of creating emulsion polymers makes use of the properties of emulsions of water
and the initiator for the reaction of the monomers. As the monomers falls through the emulsion of
water and initiator, they are formed into micelles by a surfactant that is also in the emulsion. The
initiator then reacts with the micelles. The product is a bunch of small polymer balls. This is what
produces latexes. Latexes may seem a liquid but it is actually a collection of very small polymer balls.
DOW Chemical, for instance, uses emulsion polymerization to make the latex coating for many of its
paper and carpet products. In addition to the emulsion polymers, asphalt and all of its products are
based on emulsions. Much research goes into forming new products from asphalt by changing the
emulsifying agent that it contains.
There are many ways that research is being done on emulsions and their uses. As stated above,
many oil companies are researching the effect of different emulsifying agents in asphalt. This research is

eing done in hopes of decreasing the foam that forms in the creation of asphalt. This foam has the
capability to form water and oil emulsions that are difficult to treat. The reduction of this froth is one
way that people are researching different emulsions. There are also companies that are trying to form a
serviceable fuel by making an emulsion of bitumen and water. They hope that this emulsion will replace
some component of the natural gas industry’s commercial usage, leaving more natural gas for the
private customers. Of course, there are always people trying to create new polymers and so new forms
of emulsion polymerization are always being researched in hopes of discovering a new latex polymer
that will have wonderfully useful properties.
It is anticipated that most of this research will continue long into the future. The asphalt
research that involves oil sands will only become more important as oil reserves in the Middle East are
destabilized by economic and violent conflict. In addition, the need for new polymers is not likely to fade
away. Emulsions and their uses are going to be researched for a long time.

References (by section)
Colloids
P. Garidel and A. Hildebrand. (2005). Thermodynamic Properties of Association Colloids.
Journal of Thermal Analysis and Calorimetry, Vol. 82 483–489.
"colloid." Encyclopædia Britannica. 2007. Britannica Concise Encyclopedia. 3 Apr. 2007
< http://concise.britannica.com/ebc/article-9361149/colloid>.
“Graham, Thomas." Encyclopædia Britannica. 2007. Encyclopædia Britannica Online.
3 Apr. 2007 .
http://www.m-w.com/dictionary/colloids
http://www.woodrow.org/teachers/ci/1992/Graham.html
http://www.synlube.com/colloids.htm
http://scienceweek.com/2003/sc031031-2.htm
http://www.eurekalert.org/features/doe/2002-01/dne-ds053102.php
http://www.all-natural.com/silver-1.html
http://www.nasa.gov/centers/glenn/about/fs12grc.html
http://exploration.nasa.gov/articles/physicalsciences_06-2002_lite.html
Emulsions
http://en.wikipedia.org/wiki/Emulsion
http://en.wikipedia.org/wiki/Emulsion_polymerization
http://www.ucalgary.ca/ench/AER/res_proj.htm
http://www.albertaventure.com/user/File/ASTech_Nov06.pdf
http://www.dow.com/emulpoly/na/index.htm