Chirality-induced copolymer blend with small chiral molecules

Achiral pi-conjugated polymers (PCP) have attracted intense interest due to their tunable optoelectronic properties, which have led to a variety of applications. Recently, blends of PCP with small chiral molecules have attracted further interest. The new features of chirality-induced PCP provide novel materials with potential applications in spin related optoelectronic devices. Here, we investigate the chirality-induced optoelectronic properties in blends of poly(9,9-dioctylfluorene-alt-benzothiadiazole) [F8BT], which is inherently achiral, with the chiral molecules PT-II-30 (S)-M and PT-II-29 (R)-M. We have used circular dichroism (CD) and circular photoluminescence (CP-PL) spectroscopies to characterize the chiro-optical properties of the blends. We show that the achiral F8BT exhibits large CD and CP-PL when blended with the molecules, indicating that chiral materials can induce chirality in achiral PCP. We have optimized the chiral properties of the polymer/chiral molecule blend by normalizing the CD and the PL dissymmetry by the absorbance and PL intensity, respectively, to obtain the g(CD) and g(PL) values.