Synthesis and self-assembly of nonamphiphilic hyperbranched polyoximes

Abstract

Nonamphiphilic hyperbranched polyoximes (HPOXs) were successfully synthesized by the polycondensation of trialdehyde and bis-aminooxy monomers with different molar feeding ratios. Various characterization techniques, such as 1D and 2D nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), and multi-detector gel permeation chromatography (GPC) were used to identify the highly branched structure of the HPOXs. Despite there being no amphiphilic block segments, HPOXs with a torispherical structure could self-assemble into nanoparticles in a mixed solution of dimethyl sulfoxide and H₂O. Besides, the modulation of the degree of branching (DB) and the terminal groups resulted in the appearance of spherical and bowl-shaped morphologies due to the change of the intra- and inter-molecular interactions. Accordingly, dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM), fluorescence spectroscopy (FL) together with ultraviolet and visible spectrometery (UV-vis) were employed to unravel the tentative mechanism of the formation of the HPOX self-assemblies. Moreover, dynamic oxime linkages and hydrogen bonds endowed the HPOX nanoparticles with pH and thermal dual responsiveness, which was confirmed by TEM measurements. HPOXs are developed to offer a novel pathway for the design of nonamphiphilic self-assemblies with dual responsiveness.