Chiral Ethylhexyl Substituents for Optically Active Aggregates of π-Conjugated Polymers

We report an efficient synthesis of chiral (2S)-ethylhexanol for functionalizing and solubilizing conjugated polymers. The alpha-substituted chiral ethylhexyl side chains were obtained through a powerful and flexible asymmetric synthesis using pseudoephedrine as a chiral auxiliary. The dependence of the properties of conjugated polymers on molecular structure is investigated by circular dichroism, fluorescence, and absorption spectroscopy on two new chiral conjugated polymers, poly(3,3-bis((S)-2-ethylhexyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT((2S)-ethylhexyl)(2)) and poly(3,3-bis((S)-2-methylbutyl)-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine) (PProDOT((2S)-methylbutyl)(2)). The properties of PProDOT((2S)-ethylhexyl)(2)) differ significantly from those of its methylbutyl analog as investigated by chiral aggregation providing insight into the role of interchain interactions in these subsecond switching electrochromic polymers.