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A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 0 9 The findings have important impli- cations for precipitation mechanisms in nanoscale or nanostructured materials, as well as in conditions associated with large numbers of lattice defects. The researchers say their aim is to contribute to the design of better high- strength, lightweight alloys that offer superior performance. monash.edu. DEPOLYMERIZING ON DEMAND Chemists at Riken, Japan, have developed a novel polymer that can be broken down into its molecular build- ing blocks and then recombined by ei- ther heating or cooling. The discovery could lead to intrinsically recyclable and sustainable plastics that depolym- erize on demand. The strong bonds in convention- al polymers make it extremely difficult to recover the monomers at the end of a plastic’s useful life. Responding to this challenge, Riken’s Takuzo Aida has been developing supramolecular polymers, in which the monomers con- nect via readily reversible noncovalent interactions. With his team, Aida developed a porphyrin-based monomer that formed a stable polymer in hydrocarbon sol- vents, but which readily depolymerized upon adding an alcohol. As expected, this depolymerized mixture repolymer- ized on cooling. “But to our great surprise,” Aida re- calls, “the depolymerized mixture also repolymerized upon heating.” To investigate this unusual phe- nomenon, the Riken group teamed up with colleagues at Eindhoven Univer- sity of Technology, the Netherlands, where they developed a computational method for analyzing supramolecular polymerization. The discovery could lead to the de- velopment of supramolecular polymers that are very stable in use, but highly Riken researchers have unraveled the complex depolymerization behavior of a material with the potential for sustainable plastic production. Courtesy of Patrice Latron/Eurelios/Look at Sciences/Science Photo Library. dynamic when the material needs to be recycled. It could also make indus- trial-scale solution processing of poly- mers more energy efficient. www.riken. jp/en, www.tue.nl/en.