Effect of Side Chains on the Low-Dimensional Self-Assembly of Polyphenylene-Based “Rod–Coil” Graft Copolymers in Solution

Abstract

We synthesized a series of “rod–coil” graft copolymers containing a laterally expanded poly-p-phenylene (PPP) backbone grafted with nonionic poly(ethylene oxide) (PEO) or ionic poly(acrylic acid) (PAA) side chains (denoted as PPP-g-PEO or PPP-g-PAA). The effect of the side chains on the self-assembly of the graft copolymers in THF–water mixed solvents was investigated. The PPP-g-PEO copolymers exhibited temperature-dependent self-assembly behavior, which is affected by the grafting percentage (GP) and the degree of polymerization (DP) of PEO. At 25 °C, which is higher than the crystallization temperature (Tc) of the PEO chains, PPP-g-PEO self-assembled into ultralong helices with controlled pitches when PN > 6lm/4b, where P represents GP, N denotes DP of PEO, lm expresses the length of a repeating unit in PPP, and b is Kuhn monomer length of a free jointed PEO chain; when PN < 6lm/4b, only nonhelical nanowires were observed. At 10 °C, which is below Tc of PEO, PPP-g-PEO self-assembled into polygonal multi...