One-pot synthesis and self-assembly of supramolecular dendritic polymers

Abstract

We report the design and synthesis of novel supramolecular dendrimers, formed by the association of X–Y₂ type single-chain polymeric building blocks Ba-(PnBuA-HW)₂, with (poly(n-butyl acrylate) PnBuA) separating the two specific interacting supramolecular moieties X (barbiturate, Ba) and Y (Hamilton wedge, HW). Based on a one-pot two-step synthesis, the mid-Ba and α,ω-HW functionalized X–Y₂ type polymer, Ba-(PnBuA-HW)₂, is generated via a direct thiol–bromo click reaction with Ba-(PnBuA-RAFT)₂, (M_n,NMR = 5.0 kDa, M_n,SEC = 4.8 kDa, Đ = 1.25, prepared via reversible addition–fragmentation chain transfer (RAFT) polymerization), successfully attaching the heterocomplementary supramolecular moieties (HW) at both chain ends in a one-pot fashion at room temperature within one hour. The so obtained Ba-(PnBuA-HW)₂ (M_n,NMR = 7.1 kDa, M_n,SEC = 6.7 kDa, Đ = 1.23) assembles into supramolecular dendritic polymers via hydrogen-bonds (H-bonds), illustrating impressive viscosity enhancement in the bulk state (at 20 °C by a factor as high as ∼1839). Atomic force microscopy (AFM) investigations reveal large but defined disc-like objects when spin-coated from a Ba-(PnBuA-HW)₂ solution, enabling to tune morphology at the mesoscale to generate hierarchical strucutures by choice of the solvent.