Amplifying Chiroptical Properties of Conjugated Polymer Thin-Film Using an Achiral Additive

Chiral conjugated polymers bearing enantiopure side chains offer the possibility to harness the effect of chirality in organic electronic devices. However, its use is hampered by the low degree of circular polarization in absorption (gabs) in most of the conjugated polymer thin-films studied. Here we demonstrate a versatile method to significantly increase the gabs by using a few weight percentages of a commercially available achiral long-chain alcohol as an additive. This additive enhances the chiroptical properties in both absorption and emission by ca. 5-10 times in the thin-films. We envisage that the alcohol additive acts as a plasticizer which enhances the long-range chiral liquid crystalline ordering of the polymer chains, thereby amplifying the chiroptical properties in the thin-film. The application of this methodology to various conjugated polymers has been demonstrated.