Researchers at the Adolphe Merkle Institute (AMI) have developed a new kind of glass that can be repaired using ultraviolet light and is the hardest optically healable supramolecular material developed to date.

Over the past few years, AMI scientists have been trying to create stimuli responsive materials that are easy to process and can perform useful functions. They have focused on supramolecular polymers, which have similar properties to plastics, but are simpler to process as well as being much easier to recycle and with better self-healing properties. 

This is part of a larger movement over the past 20 years in the field of supramolecular materials that has led to the development of many new and interesting materials with a wide variety of functionalities such as debonding on demand. However, only a few are produced because most of these materials lack the necessary qualities to be commercially viable, notably a resistance to mechanical stress.

Prof. Christoph Weder’s Polymer Chemistry & Materials group at AMI has however developed design concepts that will allow scientists to review their approach to molecular architecture and to develop structural materials with new functions. 

This requires the use of a low-molecular-weight multifunctional building block to form a dynamic, disordered supramolecular network, which can readily be frozen into a glassy solid.  PhD student Diederik Balkenende took this concept to design a new type of glass that matches higher stiffness and the capacity to heal using light, two properties that have proven elusive to combine in the past. Up until now, only the healing aspect had been successful.

Balkenende used a low-weight monomer to build a polymer network with a cross-linked architecture and multiple connections. The resulting glass is much stiffer than other supramolecular polymers, but can also be easily used as a coating and remain bonded to a surface.

At the same time, the network can be broken up easily and liquefied by applying an ultraviolet light similar to those used by dentists. This means a scratch on the surface can be repaired in seconds or that the coating can be removed easily.

The concept could be applicable to other supramolecular glasses made of multifunctional monomers that bind together to create a specific network and reacting to heat or light.  However, the new glass developed at AMI still requires more work to become tougher and less brittle.

The results of this research were published online at Nature Communications:

http://www.nature.com/ncomms/2016/160317/ncomms10995/full/ncomms10995.html#ref23 doi:10.1038/ncomms10995