A putative new class of materials dubbed light-stabilized dynamic materials, LSDMs, has been developed by researchers in Australia and their colleagues. Details of these potentially green materials are outlined in the Journal of the American Chemical Society [Barner-Kowollik et al. J. Am. Chem. Soc., (2019); DOI: 10.1021/jacs.9b05092]

Christopher Barner-Kowollik of Queensland University of Technology and colleagues there and at Ghent University, Belgium, and Karlsruhe Institute of Technology, Germany suggest that the development of synthetic materials that are as dynamic as those found in nature could have applications in a wide range of technological areas as well as offering ease of recycling.

Using off-the-shelf compounds - the "moth-ball" compound naphthalene and triazolinediones - the team has made materials that switch properties when illuminated by a green light-emitting diode (LED) but revert to their original form in darkness. The materials have properties that might be tenable in three-dimensional (3D) printing. In the green glow the materials are strong and stable but the links between the components break apart, reversibly, in the darkness, making it fluid again. The intriguing point here is that rather than using light to break bonds, a fairly well-known phenomenon; it is the absence of light that triggers the change. This type of chemical system is an out-of-equilibrium system. The energy from the green light sustains the bonded form away from equilibrium. No light and the system drops back to its relaxed, lowest energy state. The team suggests that pundits had suggested this might not be achievable.

"We are hoping to introduce LSDMs as a whole new class of materials, explains Hannes Houck who is associated with all three institutes."We debated whether to patent the new material, but decided not to wait and to publish the findings to advance knowledge and understanding of the processes involved."

The first applications of LSDMs might be as temporary bridges or support scaffolds for printing complicated 3D components. One form of 3D printing is additive, which makes it very useful but also difficult to make certain types of component with sharp angles. If an LSDM can be printed under green LED light and another layer added, the LSDM could then be simply poured away when the light is switched off leaving behind the requisite component.

The LSDMs might also be used in cell biology to act as supports for the cell surface without damaging the cell being studied.