Molecular Insights on Morphology, Composition, and Stability of Mixed Micelles Formed by Ionic Surfactant and Nonionic Block Copolymer in Water Using Coarse-Grained Molecular Dynamics Simulations

Abstract

The nanoscale association domains are the ultimate determinants of the macroscopic properties of complex fluids involving amphiphilic polymers and surfactants, and hence, it is foremost important to understand the role of polymer/surfactant concentration on these domains. We have used coarse-grained molecular dynamics simulations to investigate the effect of polymer/surfactant concentration on the morphology of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, i.e., pluronics or poloxamers) block copolymer, and ionic surfactants sodium dodecyl sulfate (SDS), mixed micelles in aqueous solution. The proclivity of the surfactant to form the mixed micelles is also probed using umbrella sampling simulations. In this study, we observed that the core of the pluronic + SDS formed mixed micelles consists of PPO, the alkyl tail of SDS, and some water molecules, whereas the PEO, water, and sulfate headgroups of SDS form a shell, consistent with experimental observations. The micelles are spherical at high-pluronic/low-SDS compositions, ellipsoidal at high-SDS/low-pluronic compositions, and wormlike-cylindrical at high-pluronic/high-SDS compositions. The transitions in micelle morphology are governed by the solvent accessible surface area of mixed aggregates, electrostatic repulsion between SDS-headgroups, and dehydration of PEO and PPO segments. The free energy barrier for SDS escape is much higher in mixed micelles than in pure SDS micelles, indicating a stronger tendency for SDS to form pluronic-SDS mixed micelles.

Exploiting Pharma 4.0 Technologies in the Non-Biological Complex Drugs Manufacturing: Innovations and Implications

“…Overall, the molecular insights gained from studying the co-assembly of an ionic surfactant and an amphiphilic triblock copolymer in aqueous media have potential applications in various complex fluid mixtures. However, the accuracy of the results relies on the coarse-grained force field used, which can be improved with more computationally expensive atomistic simulations for quantitative comparisons with experimental data [88].…”

Role of Unimers to Polymersomes Transition in Pluronic Blends for Controlled and Designated Drug Conveyance

“…38 Another study incorporated paclitaxel (PTX) drugs into a binary system of Pluronic L101 and P105 for the treatment of multidrug-resistant diseases. 40 By combining hydrophilic (F68, F87, F127, P85, P105) and hydrophobic (L61, L81, L101, L121) Pluronic, mixed micelles have been prepared and characterized. 38 Patel et al examined the self-assembly and phase behavior of the P123 + F127 system with an enhanced quercetin (QCT) solubilization.…”

“…They found an increase in the aggregation number at lower concentrations and a micellar phase-to-lamellar phase transition when the concentration was raised. 40 Albano et al employed MD simulations to investigate the characteristics of Pluronic F127 within micellar and lamellar phases. 41 Nie et al revealed that Pluronic micelles can attain drug-loading capacities of 80%.…”

“…Bhendale et al found an open- to folded-chain structural change upon increasing the concentration of Pluronic L64 through coarse-grained (CG) simulations. They found an increase in the aggregation number at lower concentrations and a micellar phase-to-lamellar phase transition when the concentration was raised . Albano et al employed MD simulations to investigate the characteristics of Pluronic F127 within micellar and lamellar phases .…”

Does freezing induce self-assembly of polymers? A molecular dynamics study

“…1–4 The molecular self-assemblies are mediated by weak, non-covalent interactions like hydrogen bonding, aromatic stacking, metal coordination, van der Waals interactions, hydrophobic interactions, and depletion forces, and they occur at diverse spatiotemporal scales. 3–12 It is an easy bottom-up approach that facilitates greater control over the size, shape, and ordering of individual molecular building blocks and produces novel supramolecular architectures with distinct chemical and structural properties. Owing to the ease of scaling and advanced biomimicking capabilities, self-assembly is widely used in the field of biomedicine, 1 drug delivery, 8 tissue engineering, catalysis, 9,10 fabrication of nanomaterials, 2,13 photovoltaics, 9 and energy storage devices.…”