Flowerlike Multipetal Structures of Nanoparticles Decorated by Amphiphilic Homopolymers

Abstract

This paper aims to address nanoparticles decorated by amphiphilic homopolymers composed of monomeric units with significantly different groups. It is shown that the amphiphilic structure of monomer units and the resulting effective surface activity cause the grafted macromolecules to combine into thin layers, which are arranged on a spherical nanoparticle, have a different curvature, and form a multipetal flowerlike structure. The conditions for the formation of multipetal structures are outlined, and the possibility of cascades of transformations with a smooth increase in the petal number and its sharp growth is revealed. The results are presented in the form of structure diagrams obtained in a computer experiment and constructed within the framework of the original analytical theory.

Hedgehog, Chamomile and Multipetal Polymeric Structures on the Nanoparticle Surface: Theoretical Insights

“…They are shown in Figure 2 . These are the so-called hedgehogs [ 35 ], when macromolecules combine into spikes radially diverging from the nanoparticle ( Figure 2 a); chamomile, when these spikes unite at the ends and form loops ( Figure 2 b) and multipetalers [ 36 ], when macromolecules combine into thin membrane-like lamellae arranged in a symmetrical manner ( Figure 2 c). The depicted structures are very different, but what they have in common are that ( i ) grafted macromolecules are joined into several basic components (spike, loop or petal); ( ii ) the basic components have solvophilic surface from B beads; A beads are hidden inside; ( iii ) the volume fraction φ of monomer units inside basic component (spike, loop or petal) is high, close to unity: φ ~1; ( iv ) the basic components can stretch, curve and interact with next to components (either spike, loop or membrane-like petal) with excluded volume repulsion and van der Waals attraction [ 49 , 50 , 51 , 52 ].…”

“…The free energies of elasticity of the basic components (spikes, loops or membrane-like petals) and their steric interactions were addressed in Helfrich approximation [ 50 , 51 , 52 ] adapted to describe core–shell structures of amphiphilic homopolymers [ 36 , 53 ]. For each of the structures (hedgehog, chamomile, multipetaler), all Helfrich terms were written out; then, their contributions were evaluated and only the significant ones were left.…”

“…The divergent cylindrical strands and lamellas were reported also for the spherical nanoparticles coated with amphiphilic homopolymers [ 35 , 36 , 37 ]. The structures are referred to as hedgehogs and multipetalers, correspondingly.…”

Hedgehog, Chamomile, and Multipetal Polymeric Structures on the Nanoparticle Surface: Computer Modelling

“…Diverging cylindrical filaments and lamellae on the surface of spherical nanoparticles have been observed when modeling nanoparticles coated with an amphiphilic homopolymer [ 48 , 49 ]. Amphiphilic homopolymers are macromolecules with complex monomer units containing groups with different affinities to the solvent [ 50 , 51 , 52 , 53 , 54 , 55 ].…”

Fibril Assembly and Gelation of Macromolecules with Amphiphilic Repeating Units

“…That means every monomer of such macromolecule contains both solvophobic and solvophilic chemical residues. This leads to the strong surface activity of amphiphilic homopolymers and allows them to self-assemble into structures resembling those formed in living systems by proteins and lipids. − Despite the fact that usually amphiphilic block-copolymers are synthetic macromolecules, which are used to mimic assembly features of biomacromolecules, , the amphiphilic homopolymers have a few advantages over them, such as facilitated polymerization protocols, higher surface activity, and ability to form unimolecular structures . Moreover, as a result of intrinsic connectivity of amphiphilic units along the chain and hence poor entropy, these homopolymers have a lower critical association concentration compared to block-copolymer analogues …”