A. New Strategy for Designing Conjugated Polymer-Based Fluorescence Sensing Films via Introduction of Conformation Controllable Side Chains

A fluorescence behavior controllable conjugated polymer (CP)-based fluorescent film was developed by chemical attaching poly(2,5-dihexadecyloxyphenyleneethynylene) (M-PPEs) onto a glass plate surface. It was revealed that the profile of the fluorescence emission spectrum of the film depended upon the polarity of its medium. This dependence has been attributed to the alteration of the conformation of the side chains of the polymer in immobilized state. In poor solvents or vapors, the side chains may adopt a compact coil conformation, resulting in aggregation of the immobilized polymers, and thereby fluorescence emission of the film is reduced because of the so-called aggregation-induced fluorescence quenching effect. Whereas in good solvents or vapors, the side chains tend to be swollen and adopt extended or loose coil structure, thereby preventing aggregation of the polymers, coupled with increasing of the fluorescence emission. Interestingly, this alteration process is fully reversible, and the retention time for each equilibration is less than I min. The film is also responsible for the changes in the compositions of mixture solvents, such as THF/methanol. In particular, two-input INH and OR logic gates were presented on the basis of the film. No doubt, this finding can be taken as a new strategy for the design of CPs and self-assembled monolayer (SAM)-based fluorescent sensing films and will definitely expand their applications.