Polyelectrolyte Complexes Formed from Conjugated Polymers: Array-Based Sensing of Organic Acids.

One fluorescent, positively charged poly(para-phenyleneethynylene) (PAE 1) forms electrostatic complexes with five negatively charged pyridine- or benzothiadiazole-containing poly(para-aryleneethynylene)s (PAE 2-PAE 6). The PAE 2-PAE 6 are less fluorescent in water and act as quenchers for PAE 1 in their electrostatic complexes C 1-C 5; the PAE-complexes (2 µm) were exposed to thirteen different carboxylic acids (50 mm) in buffered aqueous solution. The fluorescence responses of the small library of electrostatic PAE-complexes towards the acids was analyzed; discrimination of all of the thirteen acids was achieved. The investigated acids include acetic, butyric, tartaric, maleic, lactic, sorbic, oxalic, aspartic, and citric acids. A random, simple, ad-hoc library of electrostatic polymer complexes, C 1-C 5, therefore discerns the thirteen carboxylic acids in water.