Diblock Copolymers Containing Metal Complexes in the Side Chain of One Block

Abstract

The synthesis of novel block copolymers with metal complexes in the side chain of the polymer and their bulk self-assembly are described. Atom transfer radical polymerization plus postpolymerization chemistry were used to synthesize these novel diblock and four-arm star diblock copolymers. One block was functionalized with an asymmetric ruthenium(II) bisterpyridine complex containing a C16 alkyl chain in the 4‘ position. 1H NMR and FT-IR were used to monitor the postpolymerization chemistry, while polarized optical microscopy, small angle X-ray scattering (SAXS), and wide-angle X-ray diffraction were used to characterize the self-assembled structures. The diblock copolymer microphase separated in the bulk to form a structure-within-structure morphology “cylinders in a sea of rods” that have spacings of 38 and 5.7 nm, respectively, and the C16 chains were crystalline. The star copolymer was birefringent in the bulk, gave a SAXS signal corresponding to 38 nm, and had crystalline C16 side chains; however, no evidence for structure-within-structure could be found in the SAXS experiments. This could be due to slow relaxation times, since the molecular weight was three times larger than the linear diblock copolymer, or frustrated packing due to the star architecture.