By tweaking the chemistry of a single polymer, researchers have created a whole family of synthetic materials that range in texture from ultra-soft to extremely rigid. The materials are 3D printable, self-healing, and recyclable, and they naturally adhere to each other in air or under water.
The researchers focused their attention on the molecules involved in the crosslinking. First, they chose a parent polymer, called prepolymer, and then chemically studded these prepolymer chains with two types of small crosslinking molecules — furan and maleimide. By increasing the number of these molecules in the prepolymer, they found that they could create materials stiffer. In this way, the hardest material they created was 1,000 times stronger than the softest.
The crosslinks are also reversible. Furan and maleimide participate in a type of reversible chemical bonding. When the temperature is high enough, these molecules come apart from the polymer chains and the materials soften. At room temperature, the materials harden since the molecules quickly click back together, once again forming crosslinks.
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