Solvent Remodeling in Single‐Chain Amphiphilic Heteropolymer Systems

Abstract

This work demonstrates the remodeling of single‐chain nanoparticles (SCNPs) upon a transition to organic solvent through molecular dynamics simulations. Methacrylate‐based random heteropolymers (RHPs), assembled via transient noncovalent linkages in water, have shown promise in an assortment of applications that harness their bio‐inspired properties. While their molecular behavior has been broadly characterized in aqueous environments, many newer applications include the use of organic solvent rather than bio‐mimetic conditions. The polymer assemblies, typically driven by the hydrophobic effect in water, are less well understood in nonaqueous solution. Here, a specific RHP system is examined which forms compact globular morphologies in highly polar or highly nonpolar environments while adopting extended conformations in solvents of intermediate polarity. The pivotal role of electrostatic interactions between charge groups in low dielectric mediums is also observed. Finally, high temperature anneal cycles are compared to room temperature transformations to illuminate barriers to remodeling upon environmental changes.

Thermoresponsive Reversible Unimer Micelles of Amphiphilic Fluorinated Copolymers

“…[15,[28][29][30][31] Furthermore, the responsive self-folding and self-assembly of copolymers, which is typically driven by the hydrophobic effect in water, is non-restricted to the use of water as a solvent. [32][33][34][35][36][37][38] As a function of the nature of the environment, the remodeling of SCNPs from a compact globular conformation (in highly polar solvents) to the reverse globule (in highly nonpolar solvents) was predicted through molecular dynamics simulations, [39] while the same copolymers exhibited unfolded extended conformations in solvents of intermediate polarity. [39,40] The present work is focused on understanding the morphology of self-assembled nanostructures of (meth)acrylate copolymers with oligoethyleneglycol and perflurohexylethyl side chains synthesized via activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) as a function of the external environment, changing from water, to organic (tetrahydrofuran [THF] and dimethylformamide [DMF]) and to perfluorinated hexafluorobenzene (HFB) solvents.…”

“…[ 32–38 ] As a function of the nature of the environment, the remodeling of SCNPs from a compact globular conformation (in highly polar solvents) to the reverse globule (in highly nonpolar solvents) was predicted through molecular dynamics simulations, [ 39 ] while the same copolymers exhibited unfolded extended conformations in solvents of intermediate polarity. [ 39,40 ]…”

“…[32][33][34][35][36][37][38] As a function of the nature of the environment, the remodeling of SCNPs from a compact globular conformation (in highly polar solvents) to the reverse globule (in highly nonpolar solvents) was predicted through molecular dynamics simulations, [39] while the same copolymers exhibited unfolded extended conformations in solvents of intermediate polarity. [39,40] The present work is focused on understanding the morphology of self-assembled nanostructures of (meth)acrylate copolymers with oligoethyleneglycol and perflurohexylethyl side chains synthesized via activators regenerated by electron transfer atom transfer radical polymerization (ARGET-ATRP) as a function of the external environment, changing from water, to organic (tetrahydrofuran [THF] and dimethylformamide [DMF]) and to perfluorinated hexafluorobenzene (HFB) solvents. Various complementary techniques, such as turbidimetry, dynamic light scattering (DLS), and small angle X-ray scattering (SAXS), were employed to elucidate the formation of self-folded thermoresponsive, reversible, intrachain nanostructures, or unimer micelles, of the amphiphilic fluorinated copolymers in solution.…”

“…Furthermore, the responsive self‐folding and self‐assembly of copolymers, which is typically driven by the hydrophobic effect in water, is non‐restricted to the use of water as a solvent. [ 32–38 ] As a function of the nature of the environment, the remodeling of SCNPs from a compact globular conformation (in highly polar solvents) to the reverse globule (in highly nonpolar solvents) was predicted through molecular dynamics simulations, [ 39 ] while the same copolymers exhibited unfolded extended conformations in solvents of intermediate polarity. [ 39,40 ]…”

Dynamic Transformation of Bio-Inspired Single-Chain Nanoparticles at Interfaces

“…29 Each monomer and the hexane molecule were 173 assigned partial charges from restrained electrostatic potential 174 (RESP) charges using Gaussian 03 Revision D.01, as in prior 175 work. [30][31][32] Temperature was controlled by a Langevin thermo-176 stat with a collision frequency of 2 ps −1 , 33 bond lengths were 177 constrained by the SHAKE algorithm with bonds involving hy-178 drogen, 34 and an isotropic Berendsen barostat was used with a 179 time constant 1.0 ps when pressure is specified. 35 If pressure is 180 not specified, the simulation is instead performed at constant vol-181 ume.…”