A team of researchers at the University of Illinois at Urbana-Champaign has recently discovered how to artificially modify polymers--specifically, polyurea--so they can easily be broken down by hydrolysis, a chemical reaction where the addition of water molecules helps separate the reactant molecules. Polymers such as polyurea are large compounds known as macromolecules and feature repeating patterns of smaller subunit molecules. In polyurea, the subunit molecule is urea, CO(NH2)2, where carbon is the central atom double bonded to the carbonyl oxygen atom and single bonded to two -NH2 groups. As a result of its structure, polyurea is generally very resistant to hydrolysis and requires modification to readily dissolve in an aqueous solution.
By bonding a large atom or functional group to the nitrogen atom in one urea sub-unit of polyurea, the C-N bond is weakened, allowing the molecule to be dissolved in water. These modified polyurea molecules have been named "hindered urea bond-containing polymeric materials" or, more simply, poly(hindered urea)s (PHUs) by head researcher and Associate Professor of Materials Science and Engineering Jianjun Cheng. Now, PHUs can be completely dissolved in aqueous solutions in just a few days. However, since this entire process is based on modifying the urea molecule by adding another molecule or atom to it, the exact conditions under which the PHU is broken down by hydrolysis can be adjusted to fit the circumstances.
Since polymers such as polyurea are frequently used in bonding, the applications for a hydrolyzable polymers, i.e. able to be dissolved via hydrolysis or exhibiting temporary bond stability in the presence of water, are numerous and immediate. Polyurea has the added benefit of being a remarkably inert compound so its interactions with other chemicals are relative few. Some possible applications of PHUs include new means of pharmaceutical drug delivery and controlled release systems of agricultural chemicals.
Submitted by Max Meirow
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