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-EGx))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 interchainπ-πinteraction 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℃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 EGxtails.This work uncovered a facile strategy to tailor the self-assembly of rigid backbone polymers for fabrication of functional nanodevices.