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 H 2 O. 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 selfassemblies. 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.

Reversible Self-Assembly of Backbone-Thermoresponsive Long Chain Hyperbranched Poly(N-Isopropyl Acrylamide)

“…The resulting polymer LCHBPNIPAM ( M n,SEC-MALLS = 44,300 Da, M w / M n = 1.27; η n = 7.0, α = 0.43) was obtained by the click chemistry of the AB 2 macromonomer ( M n,SEC-MALLS = 4200 Da, M w / M n = 1.20) according to our previously work [ 38 ]. Generally, the backbone-thermoresponsive hyperbranched polymer based on hydrophilic-hydrophobic balance can self-assemble to form multi-compartment vesicles below lower critical solution temperature (LCST), and the micelles aggregate to larger particles above LCST [ 39 , 43 , 44 , 45 , 46 , 47 ]. Thus, the thermo-induced reversible self-assembly behavior of LCHBPNIPAM with an intensely increasing Z-average diameter ( D z ) values at 35 °C (LCST point) ( Figure 1 B) was easily promoted via directly dissolving it in water with a concentration of 0.2 mg/mL at a cyclic temperature of heating from 20 to 65 °C, and then cooling to 20 °C.…”

Bioapplications of hyperbranched polymers

“…To date, a series of acid-cleavable HBPs have been designed and applied in biological and biomedical fields to obtain pH-sensitive materials. [40][41][42][43][44][45] Introducing pH-sensitive moieties into HBPs endows them with responsive capacity. Current approaches toward the development of pH-responsive HBPs involve either the incorporation of ''titratable'' groups including amines or carboxylic acids into the terminal group of HBPs or the introduction of acid liable linkages such as acylhydrazone or oxime into the backbone of HBPs that degrade under acidic conditions.…”

How does a tiny terminal alkynyl end group drive fully hydrophilic homopolymers to self-assemble into multicompartment vesicles and flower-like complex particles?

“…Compared with the above-mentioned simple linear structure, amphiphilic homopolymers with unique non-linear topologies, such as Y-shaped, 37 cyclic, 38 hyperbranched, [39][40][41] and dendronized, 42 have exhibited some unusual self-assembly behaviour and interesting applications. Therefore, we intend to introduce a kind of simple and usual end group into hydrophilic linear or non-linear homopolymers to drive their selfassembly in aqueous solution.…”