Researchers at the Adolphe Merkle Institute, in collaboration with the Technical University of Darmstadt, have developed a new type of polymer - the main component of plastics - that is more easily degradable than conventional materials. Mechanical treatments, such as grinding, combined with alkaline water, are all that is needed to facilitate degradation and reduce their environmental impact.

According to UN figures, humanity produces "around 430 million tons of plastics every year”. Through littering and inadequate disposal, a substantial amount of plastic enters the environment where it negatively affects plants and wildlife as well as human health. Developing more environmentally-sustainable plastics is as crucial as it is urgent for our planet. This is the challenging goal of an international research group that is part of the NCCR Bio-inspired Materials and includes four researchers from the Adolphe Merkle Institute at the University of Fribourg.

Plastic are both excellent and dreadful
Plastics are made up of long chains of molecules called polymers. Extremely strong and stable, these molecular chains are highly resistant to natural decomposition processes which explains why they accumulate in the environment. To remedy this, researchers from the Adolphe Merkle Institute, in collaboration with colleagues from the Technical University of Darmstadt and the University of Strathclyde, have developed new chemical structures that allow for breaking the bonds of polymer molecules more easily, and thus facilitating degradation.

Easier elimination of plastics
The scientists designed a new cyclobutene motif, a molecule from the hydrocarbon family, that can be integrated into many common plastics. "When incorporated into polymer molecules, this chemical compound enables them to break down into smaller molecules under the action of mechanical forces and an alkaline solution," explains Peng Liu, a polymer chemistry specialist from the Adolphe Merkle Institute. It is this property that facilitates the chemical degradation of plastics, helping to reduce environmental pollution.

Degradation on demand
The main challenge in designing biodegradable polymers is that they should not degrade prematurely, i.e., while they are in use. "This problem is solved with the new cyclobutene motif," explains Christoph Weder, Professor at the Adolphe Merkle Institute. "Our new motif effectively acts as a degradation switch. The switch is triggered under environmental conditions that combine mechanical forces and alkaline conditions, like the ones found in our oceans. With this solution, we envision that plastics that incorporate our new chemical motif can be more readily broken down and disposed of.”

Mechanically triggered on-demand degradation of polymers synthesized by radical polymerizations , Nature Chemistry