Polyureas are relatively inexpensive and easy to synthesize, plus they tend to be highly resistant to breaking down, making them useful for coatings, adhesives, and other applications requiring durability. Hanze Ying and Jianjun Cheng of the University of Illinois, Urbana-Champaign, have now changed the game for the polymers by designing and synthesizing a class of easily hydrolyzable polyureas (J. Am. Chem. Soc. 2014, DOI: 10.1021/ja5093437). They report that adding a bulky substituent such as a tert-butyl group to polyureas destabilizes the polymer backbone and makes it more susceptible to hydrolysis, causing degradation in a few days. The new polymers could be useful for drug delivery, tissue engineering, controlled release, and other applications in which polymer breakdown in aqueous solution is desirable. Modifying the size and nature of the bulky substituents could also enable tight control over the degradation rate, the researchers note, although Cheng’s group has not confirmed that yet. Other types of hydrolyzable polymers exist, but the new polyureas are more readily synthesized than most, without catalysts or generation of by-products, Cheng says. The toxicity of the breakdown products, however, will have to be evaluated before biomedical, food, or agricultural applications can be considered.