POLYMER/PLASTIC OPTICS: Optical polymers heal themselves with light

摘要

Researchers at Case Western Reserve University (Cleveland, OH), the US Army Research Laboratory (Aberdeen Proving Ground, MD), and the University of Fribourg (Fribourg, Switzerland) have developed a class of optically active metallosupramolecular polymers that are "healed" upon exposure to light, extending their useful life in applications that range from automotive paints to everlasting compact disks. Although several-micron-deep cracks and surface blemishes on conventional thermoplastic optical polymers can be healed by heating them above their glass-transition temperature, the process is slow and inefficient, because it involves wetting, diffusion, and re-entanglement of the high-molecular-weight polymer chains. However, these processes can be avoided by exploiting thermally reversible covalent bonds in lower-molecular-mass species such as metallosupramolecular polymers. For these "tough" polymers, heating (with light used to locally apply heat) reduces the viscosity of the materials so that defects can be healed before the polymer is reformed.