Self-Assembly and Optical Property of Triblock Copolymers Made of Polystyrene and Oligo(p-phenyleneethynylene) in Different Mixtures of Toluene and Hexane

Abstract

Using a combination of laser light scattering (LLS), UV−vis, and fluorescence spectrometry methods, we comparatively examined the self-assembly and optical property of two triblock copolymers made of polystyrene (PS, coillike) and oligo(p-phenyleneethynylene) (OPE, rodlike) in different mixtures of toluene and hexane. For the coil−rod−coil (PS−OPE−PS) triblock copolymer, intrachain wrapping of the two soluble PS coil blocks on the insoluble middle OPE rod block in the solvent mixture reduces the π−π stacking of OPE and makes it more planar, resulting in a red shift in its UV−vis and fluorescence spectra, presumably, due to the J-type aggregation. While for the rod−coil−rod (OPE−PS−OPE) triblock copolymer, two intrachain stacked insoluble OPE blocks are wrapped and stabilized by the soluble middle PS block in toluene. The addition of hexane, a nonsolvent of PS, leads to further interchain aggregation of OPE, resulting in large polymeric micelles with an insoluble OPE core and a soluble PS shell. The blue s...