2D Self-assembly of an amido-ended hyperbranched polyester induced by platinum ion coordination effect

Abstract

Compared with amphiphilic hyperbranched polymers (HBPs), the self-assembly of hydrophilic HBPs remains a challenging area. In this article, we report the self-assembly of an amido-ended, hydrophilic hyperbranched polyester (HTDA-2), by taking advantage of the induction effect of the platinum ion. Self-assembled HTDA-2-Pt polymers are composed of ordered 2D tree-like structures with a diameter of about 500 μm and a trunk-width of approx. 1–2 μm, as shown by transmission/reflection polarizing optical microscopy (TRPOM), scanning electron microscopy (SEM) and dynamic light scattering (DLS). Factors such as temperature, time, solvent, concentration and humidity which influence the morphology of the self-assemblies were investigated using XPS, XRD, SEM, and FT-IR techniques. It is proposed that the coordination between the platinum and oxygen atoms in the amido groups together with hydrogen bonding may induce individual aggregation of core chains and peripheral chains, resulting in micro-phase separation and formation of micelles. These micelles then aggregate and self-assemble into perfect tree-like structures on the surface of a glass substrate in a limited region. The dimension (D_f) of about 1.59 for the fractal tree-like morphology suggests perfect fractal behavior of the self-assemblies. Another interesting finding is the appearance of crystal behavior of the tree-like self-assemblies as revealed by XRD analysis.