New catalyst crafted for making biodegradable plastics

Researchers with Stanford university and Research Labs at International Business Machine Corporation (IBM) have developed new chemical approaches to generating biodegradable plastics efficiently and inexpensively.

As creating biodegradable polyesters requires the assistance of a catalyst, namely a special class of chemical that increases the rate of a reaction or pushes it over an energetic hurdle, the standard catalysts used are metal-based, which are difficult or expensive to remove from the final material, and do not degrade in the environment.

In their study, published in the current issue of Nature Chemistry, the research group headed by Robert Waymouth of Stanford and James Hedrick of IBM Research presents an alternative catalyst that is both fast and selective, exceling at accelerating and facilitating reactions and that it does not alter the resulting polymer' s shape or properties once it is formed.

The catalyst is crafted by reacting common chemical ingredients - thiourea with a metal alkoxide.

"While many catalysts are either fast or selective, these catalysts are both," Waymouth was quoted as saying by a news release from Stanford. "They are simple to prepare, easy to use and can be readily adopted by anyone with a basic knowledge of chemistry."

In addition to lowering the cost and environmental impact, the new catalyst design is highly tunable, said Waymouth, a professor in chemistry at Stanford. The work can produce polylactic acid, a commercial compostable biodegradable polyester utilized in disposable plasticware, such as tableware, cups, plates and forks. It has medical applications for resorbable sutures, implants and stents, as well as biomedical implants and drug-delivery materials. Everyday items such as food packaging and non-woven fabrics are also a possibility.

The results, based on a decade of research, are just the first steps, the researchers said.

Because the technique is relatively simple and the catalysts are readily modified, these advances could lead to new and broadly useful class of catalysts - and likewise, new and useful biodegradable plastics. "Our catalyst design is simple and general and could prove useful not only for polymerization but for a wide range of organic reactions," said Xiangyi Zhang, the Stanford graduate student who conducted the experimental work. Endit