Polymer Self-Assembly into Unique Fractal Nanostructures in Solution by a One-Shot Synthetic Procedure

Abstract

A fractal nanostructure having a high surface area is potentially useful in sensors, catalysts, functional coatings, and biomedical and electronic applications. Preparation of fractal nanostructures on solid substrates has been reported using various inorganic or organic compounds. However, achieving such a process using polymers in solution has been extremely challenging. Here, we report a simple one-shot preparation of polymer fractal nanostructures in solution via an unprecedented assembly mechanism controlled by polymerization and self-assembly kinetics. This was possible only because one monomer was significantly more reactive than the other, thereby easily forming a diblock copolymer microstructure. Then, the second insoluble block containing poly(p-phenylenevinylene) (PPV) without any side chains spontaneously underwent self-assembly during polymerization by an in situ nanoparticlization of conjugated polymers (INCP) method. The formation of fractal structures in solution was confirmed by various imaging techniques such as atomic force microscopy, transmission electron microscopy (TEM), and cryogenic TEM. The diffusion-limited aggregation theory was adopted to explain the branching patterns of the fractal nanostructures according to the changes in polymerization conditions such as the monomer concentration and the presence of additives. Finally, after detailed kinetic analyses, we proposed a plausible mechanism for the formation of unique fractal nanostructures, where the gradual formation and continuous growth of micelles in a chain-growth-like manner were accounted for.

Stimulus-responsive Self-Assembly of Protein-Based Fractals by Computational Design

“…Many fractal fabrication efforts have relied on top-down patterning of surfaces 9 . The bottom-up design of supramolecular fractal topologies – both deterministic (e.g., Sierpinski’s triangles) 10,11 and stochastic fractals (e.g., arborols) 12,13 – has been performed with small molecule building blocks such as inorganic metal-ligand complexes or synthetic dendritic polymers utilizing co-ordinate or covalent bonds, respectively. Self-similar quasi-fractal shapes built with DNA origami have been reported 14–16 , however, fractal topologies have not been designed with proteins, which possess a wide range of functionality, biocompatibility, and whose properties are dynamically controllable by reversible post-translational modifications 17 .…”

Self‐Assembly of Di‐Guanine Peptide Nucleic Acid Amphiphiles into Fractal Patterns

“…Prolonged incubation of the compound for 30 days at 4 °C resulted in extended aggregation to form structures as shown in Figure f, which eventually led to the formation of fractal patterns as shown in Figure g. Here the nanorods are known to act as nucleation sites for the chain‐like growth of the aggregate leading to continuous formation of new branches resulting in fractal patterns . The formed fractal appears to be dendritic in nature.…”

“…Fractal nanostructures exhibit high surface area and present several promising applications in sensors, catalysis, biomedicine and electronics. Different inorganic and organic compounds and polymers have been used to prepare fractal patterns . The physico‐chemical principles that support the fractal formation have remained subtle and hence the bottom up construction of fractals is challenging …”

Synthesis of Well‐Defined Poly(norbornene) Containing Carbon Nanodots by Controlled ROMP

“…ROMP of NB‐HBC with an M/I ratio of 100 at 0.1 M afforded a polymer molecular weight ( M n ) of 116 kDa with a moderate dispersity of 1.36 (Table , entry 1). To reduce this dispersity, we added a common solvent for ROMP, THF as a cosolvent, but this increased the dispersity to 1.43 (Table , entry 2) presumably due to π–π interaction of the HBC moiety or aggregation of the polymers (see the Supporting Information for further details), causing less ideal polymerization in the less soluble THF (Table , entry 2). To suppress the π–π interactions, we lowered the concentration to 0.05 M in CF and the polymer with a narrow dispersity of 1.24 was prepared with full consumption (Table , entry 3).…”

“…The ROMP of norbornene (NB) derivatives has become a powerful tool to synthesize complex macromolecules including block copolymers, graft‐polymers, and dendronized polymers . Despite the versatility of the ROMP, its synthetic application for the production of polymers with PAH moieties has been rarely investigated.…”