No. 389: An organic material that becomes liquid by ultraviolet radiation and returns to be a solid by heating (December 24, 2011)

A research group led by Dr. Yasuo Norikane of National Institute of Advanced Industrial Science and Technology developed an organic material that becomes liquid by ultraviolet irradiation and returns to a solid by heating. The newly developed material couples azobenzene in a circular pattern and allows for an endless repetition between liquefaction and solidification. When it is in a solid state, it is liquefied if it is irradiated by ultraviolet. If the liquefied sample is heated, it becomes a solid through crystallization and returns to liquid if the crystal is irradiated by ultraviolet. It does not show any deterioration even if liquefaction and solidification was repeated 10 times.

It is known that particles of azobenzene change with irradiation and heating, but the change is supposed to occur only in solution. There has been no such material that can change between solid and liquid endlessly with the help of the response of a compound to light. The research team thinks that the new material can be applied to a recyclable photoresist and a new kind of adhesive. It will make further efforts to improve the reaction efficiency of the new material to put it into practical use because its reaction efficiency is still low.