Synthesis, Chiroptical Behavior, and Sensing of Carboxylic Acid Functionalized.Poly(phenylene ethynylene-alt-bithiophene)s

Several poly(phenylene ethynylene-alt-bithiophene)s with (chiral) nonfunctionalized substituents were synthesized with a variable phenylene ethynylene (PE) spacer length (up to 4 repeating units). The chiroptical behavior was evaluated with UV vis and circular dichroism (CD) spectroscopy, revealing a highly solvent-sensitive aggregate formation. Based on this high sensitivity, both chiral and achiral carboxylic acid functionalized analogues were prepared, of which the length of the spacer connecting the carboxylic acid to the polymer backbone was varied. A combination of UV vis, CD, and emission spectroscopy showed a clear affinity of chiral amines toward the functionalized polymers both in solution and in film. However, a different supramolecular behavior of the polymers was observed depending on the length of the carboxylic acid functionalized side chain.status: publishe