Regulating the self-assembly of rigid 2D ribbon-like amphiphilic homopolymer via tailoring its holistic conformation

Amphiphilic rigid backbone polymers are traditionally seemed as one-dimensional (1D) rods and show distinct self-assembly behavior to flexible polymers, but they could hardly adapt morphology-tunable self-assembly by changing their holistic conformation upon external stimuli. In this study, we synthesized a series of amphiphilic homopolymers poly(acetylene azobenzene oligoethylene glycol) (P(AAzo-EG x )) containing conjugated polyacetylene mainchain, azobenzene pendants and oligo ethylene glycol tails in each unit. This comb-like amphiphilic polymer could be treated as two-dimensional (2D) nanoribbons with tunable holistic conformation via meticulous tailoring intrastrand repulsion and interchain π-π interaction of azobenzene pendants by light, temperature, and solvent swelling. P(AAzo-EG 2 ) could self-assemble into large vesicles in ambient, whereas transformed to supramolecular helix bundles (SHBs) at 65 °C as well as depicted by dissipative particle dynamics (DPD) simulation, and then turned into grass leaf-like micelles upon sequential ultraviolet (UV) and blue light irradiation. The three assemblies featured different stacking mode of PAAzo skeletons although showed similar aggregate induce emission (AIE) effect. In this holistic macromolecular chain conformation-induced self-assembly and morphology transformation, temperature influenced the stacking of hydrophobic parts mainly by tuning the torsion of PAAzo skeleton. Certain amount of good solvent played a vital role by swelling of hydrophobic PAAzo skeleton, and helping the movement and rearrangement of azobenzene pendants and polyacetylene mainchains like a lubricant. The length and diameter of SHBs could be tuned by changing EG x tails. This work uncovered a facile strategy to tailor the self-assembly of rigid backbone polymers for fabrication of functional nanodevices.