Mussels extend hair-like fibers that attach to surfaces using plaques of
adhesive. Proteins in the glue contain the amino acid DOPA, which harbors the
chemistry needed to facilitate the "cross-linking" of protein molecules,
providing strength and adhesion. Purdue researchers have now combined this
bonding chemistry of mussel proteins with a polymer called poly(lactic acid), or
PLA, a bio-based polymer that can be derived from corn. The adhesive was created
by harnessing the chemistry of compounds called catechols, contained in
"We found the adhesive bonding to be appreciable and comparable to several
petroleum-based commercial glues," Wilker said.
Findings are detailed in a research paper published online Jan. 4 in the
journal Macromolecules and to appear in an upcoming print issue of the
journal. The paper was authored by Wilker and graduate students Courtney L.
Jenkins and Heather M. Siebert in Purdue's Department of Chemistry. Jenkins is
now an assistant professor of chemistry at Ball State University.
"Results presented here show that a promising new adhesive system can be
derived from a renewable resource, display high-strength bonding, and easily
degrade in a controlled fashion," Wilker said. "Particularly unique was the
ability to debond this adhesive under mild conditions."
Early adhesives were made of natural materials such as starch, but have been
replaced in recent decades with synthetic glues possessing superior performance.
About 9 billion kilograms of glue are now manufactured annually in the United
States, with nearly 4 billion kilograms containing formaldehyde.
"The detrimental health and environmental effects of synthetic glues are
becoming more of a concern, with alternatives being developed," Wilker said.
"Renewable, nontoxic, and removable adhesives are thus in great demand to
decrease our exposure to pollutants as well as waste in landfills."
The researchers tested the adhesive by measuring the force needed to pull
apart metal and plastic plates bonded together, finding that it compared
favorably with various commercial products. Unlike synthetic glues, however, the
be easily degraded in water.
"This new system may help lead us toward nontoxic materials sourced from
nature, capable of being broken down into benign components, and enhanced
recyclability of the products all around us," Wilker said.