Self‐assembly mechanism of PEG‐ b ‐PCL and PEG‐ b ‐PBO‐ b ‐PCL amphiphilic copolymer micelles in aqueous solution from coarse grain modeling

Journal Article · Wed Mar 03 00:00:00 EST 2021 · Journal of Polymer Science

DOI:https://doi.org/10.1002/pol.20200864· OSTI ID:1778371

Sadeghi, Maryam S.  ^[1]; Moghbeli, Mohammad Reza  ^[1]; Goddard, III, William A.  ^[2]

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1. Smart Polymers and Nanocomposites Research Group, School of Chemical Engineering Iran University of Science and Technology Tehran Iran
2. Materials and Process Simulation Center (MSC) California Institute of Technology Pasadena California USA

Abstract We followed the self‐assembly of high‐molecular weight MePEG‐ b ‐PCL (poly(methyl ethylene glycol)‐ block ‐poly(ε‐caprolactone)) diblock and MePEG‐ b ‐PBO‐ b ‐PCL (poly(methyl ethylene glycol)‐ block ‐poly(1,2‐butylene oxide)‐ block ‐poly(ε‐caprolactone)) into micelles using molecular dynamics simulation with a coarse grain (CG) force field based on quantum mechanics (CGq FF). The triblock polymer included a short poly(1,2‐butylene oxide) (PBO) at the hydrophilic‐hydrophobic interface of these systems. Keeping the hydrophilic length fixed (MePEG ₄₅ ), we considered 250 chains in which the hydrophobic length changed from PCL ₄₄ or PBO ₆ ‐ b ‐PCL ₄₃ to PCL ₆₂ or PBO ₉ ‐ b ‐PCL ₆₁ . The polymers were solvated in explicit water for 2 μs of simulations at 310.15 K. We found that the longer diblock system undergoes a morphological transition from an intermediate rod‐like micelle to a prolate‐sphere, while the micelle formed from the longer triblock system is a stable rod‐like micelle. The two shorter diblock and triblock systems show similar self‐assembly processes, both resulting in slightly prolate‐spheres. The dynamics of the self‐assembly is quantified in terms of chain radius of gyration, shape anisotropy, and hydration of the micelle cores. The final micelle structures are analyzed in terms of the local density components. We conclude that the CG model accurately describes the molecular mechanisms of self‐assembly and the equilibrium micellar structures of hydrophilic and hydrophobic chains, including the quantity of solvent trapped inside the micellar core.

• Sponsoring Organization: USDOE
• Grant/Contract Number: DE‐AC05‐00OR22725; DE‐SC0017710
• OSTI ID: 1778371
• Journal Information: Journal of Polymer Science, Journal Name: Journal of Polymer Science Vol. 59 Journal Issue: 7; ISSN 2642-4150
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: United States
• Language: English