The Power of Transesterification - Making Biodiesel and Turning an Organic Network into Glass

You may not have heard of transesterification but probably heard about the compound this reaction produces: biodiesel. As a general reaction, it involves taking an ester and an alcohol and changing them into a different ester and alcohol.

You can think of this as transforming one ester into another. In the synthesis of biodiesel, transesterification typically starts with a fat which is a triester molecule. After reacting with methanol and a catalyst, a high yield of methyl esters or biodiesel can be collected.

 

Image from Dogpatch Biofuels

A few years ago this reaction was discovered to be highly useful in taking an organic polymeric network and turning it into a resin that has the hardness of glass, the ability to be reshaped, and is recyclable. Researchers Damien Montarnal, Mathieu Capelot, François Tournilhac, and Ludwik Leibler from Laboratoire Matiere Molle et Chimie in Paris, France modified bisphenol A diglycidyl ether with some di- and tricarboxylic acids to create an organic polymeric network with ester and alcohol functional groups.

 

Credit: Cyril Fresillon/CNRS

The stoichiometry and reversibility of this reaction allow the number of ester and alcohol groups to remain the same. The flexibility in changing how cross-links are formed enables this material to adopt various complex shapes.

For further reading, check out:

*A Plastic that Behaves Like Glass by Bethany Halford

*New revolutionary material can be worked like glass (press release)

*Silica-Like Malleable Materials from Permanent Organic Networks by Damien Montarnal, Mathieu Capelot, François Tournilhac, and Ludwik Leibler; Science 18 November 2011: Vol. 334 no. 6058 pp. 965-968; DOI: 10.1126/science.1212648

 

Chemistry in a Work of Art - Light Spectra by Bev Precious

Light Spectra by Bev Precious, an aluminum and dichroic glass sculpture in the foyer of the chemistry building at UW-Madison (photo by Jeff Miller)

The first thing a visitor might see upon entering the foyer of the chemistry building at UW-Madison is a brilliant aluminum and dichroic glass sculpture suspended overhead. "Light Spectra" was created in 2001 by American sculpture Bev Precious who used the interplay of metal and dichroic glass to create an eye-catching work of art.

The creation of dichroic glass involves a process called electron beam physical vapor deposition, where 10,000 V of electricity are concentrated in an electron beam and vaporizes a mixture of quartz and metal oxides of titanium, chromium, aluminum, zirconium, or magnesium. This mixture vapor is eventually deposited onto a glass surface and can be applied a layer at a time. Layer thicknesses are precisely controlled to allow multiple colors to be produced on the same glass.

Image from Center for Nanoscale Science and Engineering

Here is a cool video, produced by a company called Coatings By Sandberg, showing how dichroic glass is made.

Geodesic pattern glass from CBS

Dichroic glass has the special property of transmitting light of one color and reflecting light in a different color. Hence as you walk around a dichroic sculpture, you would see different colors evolve at different angles of observation.