Modulation of stimuli-responsiveness toward acid vapor between real-time and write-erase responses based on conjugated polymers containing azobenzene and Schiff base moieties

Abstract

We developed three types of film-type stimuli-responsive polymers based on aza-substituted conjugated polymers involving azobenzene, N_bith, N_fluo and Schiff base moieties, C_bith. All polymer films showed bathochromic shifts in absorption spectra followed by chromic behaviors by fuming trifluoroacetic acid (TFA). In particular, we disclosed that there were three significant differences on acid detecting ability between azobenzene and Schiff base derivatives in terms of absorption wavelengths, stability, and proton holding time. The azobenzene polymers exhibited real-time responses toward vapor fuming, meanwhile write and erase chromic behaviors were reversibly accomplished with the Schiff base polymer by exposing to acid and amine vapor. Theoretical calculation revealed that red-shifted absorption bands should be induced by protonation on nitrogen atoms in the aza-substituted positions. Diverse responses through dynamic regulation of electronic properties of main-chain conjugation can be accomplished by introducing the aza-substituents in polymers.