Change colors

The institute's scientists have developed a method that makes it possible to produce glasses that change colors and become darker as they are exposed to stronger solar radiation. all the colors of the rainbow 

 
From the right: Dr. Dimitri Friedland, Dr. Lev Pinkin, Dr. Judith Ratner, Prof. Valerie Krongause, Dr. Alexander Schiff, Dr. Boris Perlmutter, Amram Masad. in the eyes of the beholder

Prof. (retired) Valery Krongause is a definite optimist, but still, pink glasses, with a fixed color, did not seem to him to be a product that might be suitable for all year round. In order to deal with changing light conditions, he developed a unique method that makes it possible to produce glasses that change colors and become darker as they are exposed to stronger sunlight.
In the darkening process, they can get all the colors of the rainbow, from yellow to red or blue.
Prof. Krongauz, from the Department of Organic Chemistry at the Weizmann Institute of Science, is known mainly for his research on the properties of photochromic organic substances - carbon-based substances that change color as a result of exposure to strong light. One of his inventions led to the founding of the Chromatic company, which currently operates in the Rabin Science Park. "Chromatic" sells photochromic materials used in the production of glasses that darken with exposure to the sun, worldwide.
Darkened glasses have become more in demand in the last two decades, with the increased awareness of the need to protect the eyes from the sun's radiation. More than 100 million pairs of such glasses are sold worldwide every year. Today, most people in developed countries buy glasses with plastic lenses, which poses a considerable challenge, because the attempts to produce a photochromic material that will fit plastic lenses, encounter significant difficulties.
The complexity and high costs involved in the production of darkening plastic lenses meant that only a few large companies in the world invested in the development of the technology necessary for their production. Most lens manufacturers cannot afford to purchase rights to use existing technology, and certainly cannot develop photochromic materials
by themselves. This gap can be closed by the manufacturers of these glasses - and also by the manufacturers of darkening layers for the glass of cars - using the materials developed by Prof. Krongause, and produced by the "Chromatic" company.
The material developed by Prof. Krongause, which is suitable for use in plastic lenses and darkens upon exposure to sunlight, is characterized by a high intensity of darkening. This feature allows manufacturers to use it in two ways: to melt it inside the plastic lenses, or to create a very thin coating on the lenses. The coating of the lens with the material is carried out in a process similar to that by which the lens is covered with a coating that protects it from scratches. This darkening material is also characterized by durability over time and great sensitivity: in response to exposure to strong light, it darkens very quickly, but when the light weakens (for example, when the person wearing glasses enters a building from the street), it returns very quickly to its original color.
These rapid color changes result from a relatively modest molecular event: a photochromic molecular structure changes color when it receives a single photon of light, which breaks just one of its chemical bonds. As soon as the light disappears, the bond returns to its place, and the photochromic molecular structure returns to its original color.
Organic photochromic substances were discovered at the Weizmann Institute of Science in 1952 by Prof. Ernst Fischer and Prof. Yehuda Hirschberg. When the Cold War was in full swing, Soviet scientists were interested in these materials, who wanted to develop glasses that would protect the eyes from blinding radiation emitted after an atomic explosion. Prof. Krongauz was then working at a large research institute for physical chemistry in Moscow, but like many other Jewish scientists, he stayed away from military research, fearing that access to the secrets of the Soviet army would prevent him from leaving the Soviet Union in the future. Prof. Krongause: "Beyond these considerations, I was always more interested in basic research, and I preferred to focus on theoretical research of photochromic materials, which attracted my attention not only because of the interesting scientific questions they represent, but also because of their aesthetic beauty."
Thus, both in his scientific work in Moscow, and also after immigrating to Israel and joining the Weizmann Institute of Science in 1976, Prof. Krongause made important contributions to the theory of photochromism and other areas of organic chemistry. He was the first to synthesize photochromic polymers. In another work, he discovered a new type of organic materials called quasi-crystals, which have unique electro-optical properties. These studies were, in fact, the first steps in the science that emerged in those days and today we call "nanoscience": research and design of materials at the level of molecular organization. Still, at the same time as his basic research, Prof. Krongaus spent several sabbatical periods at large companies such as Xerox and Dow, and was also interested in applied research. One of his applied projects led (in 1999) to the establishment of the "Chromatec" company, where he currently serves as chief scientist. This company, which was established under a license from the "Yade" company, the applied arm of the Weizmann Institute of Science, and in collaboration with Amram Masad, an expert in optical lenses who serves as CEO and president of the company, currently employs about half a dozen chemists, all of whom have a doctorate degree - and all of whom are from Russia.
The company has already developed about 500 different photochromic molecules, and it can adapt these molecules to the needs of customers on demand. So, for example, they can control the speed of darkening, and the shade that will be obtained with the darkening. In different parts of the world, people prefer sunglasses in different shades. In the USA they like gray, in Europe they prefer brown, in Brazil they ask for green lenses, and in India there is a demand for lenses
In fashionable shades, such as purple, orange and burgundy. In addition to all these, in many countries there is a demand for "driver's glasses", which in the darkening process change color, from yellow to gray.
Prof. Krongaus and members of his research group are meanwhile working on future applications. One possible direction is the development of darkening crystals that would be suitable for implantation inside the eye in cataract removal surgery instead of the natural crystal, to protect the eye from strong radiation. Another promising direction is the development of plasma technology that will allow surfaces to be covered with a thin film of darkening material using steam - under vacuum conditions.
Photochromic materials are currently sold in the world market at a price of about 50 thousand dollars per kg - almost twice the price of gold. The steadily increasing volume of sales is another reminder of the way in which basic research contributes to the development of advanced consumer products.