Stepwise blue-red-yellow color change of a polydiacetylene sensor through internal and external transitions

Abstract

A reversible red-yellow color change in PDA (polydiacetylene) was achieved by controlling the head group of the diacetylene molecules. Typical PDAs show blue-red color transitions, and this reversible red-yellow color transition could be applied to various sensing applications. The introduction of an alkyl substituent to the head group as an internal stimulus resulted in a primary blue-red color change, and this change became clearer as the length of the alkyl chain became longer. The PDA vesicle, once colored red in response to an internal stimulus, showed a reversible and very selective red-yellow color change in response to a second external stimulus, such as temperature or pH.