Researchers have developed a new type of rubber that is as tough as natural rubber but can also self-heal. Applications include wearable electronics and other medical devices. In order to make a rubber self-healable, the team needed to make the bonds connecting the polymers reversible, so that the bonds could break and reform.

They developed a hybrid rubber with both covalent and reversible bonds. The concept of mixing both covalent and reversible bonds to make a tough, self-healing rubber was proposed in theory but never shown experimentally because covalent and reversible bonds don’t like to mix.

So, the researchers developed a molecular rope to tie these two types of bonds together. This rope, called randomly branched polymers, allows two previously unmixable bonds to be mixed homogeneously on a molecular scale. In doing so, they were able to create a transparent, tough, self-healing rubber.

They researchers say the concept of using molecular design to mix covalent and reversible bonds to create a homogenous hybrid elastomer and should enable development of tough, self-healing polymers of practical usage.