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Abstract Polymer‐grafted hybrid materials have been ubiquitously employed in various engineering applications. The design of these hybrid materials with superior performances requires a molecularly detailed understanding of the structure and dynamics of the polymer brushes and their interactions with the grafting substrate. Molecular dynamics (MD) simulations are very well suited for the study of these materials which can provide molecular insights into the effects of polymer composition and length, grafting density, substrate composition and curvatures, and nanoconfinement. However, few existing tools are available to generate such systems, which would otherwise reduce the barrier of preparation for such systems to enable high throughput simulations. Here polyGraft, a general, flexible, and easy to use Python program, is introduced for automated generation of molecular structure and topology of polymer grafted hybrid materials for MD simulations purposes, ranging from polymer brushes grafted to hard substrates, to densely grafted bottlebrush polymers. polyGraft is openly accessible on GitHub (https://github.com/nanogchen/polyGraft).
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Nanoparticle Brushes: Macromolecular Ligands for Materials Synthesis
In this Account, we describe our recent work in developing polymer brush coatings for nanoparticles, which we use to modulate particle behavior on demand, select specific nanoscopic architectures to form, and bolster traditional bulk polymers to form stronger materials by design. Distinguished by the polymer type and capabilities, three classes of nanoparticles are discussed here: nanocomposite tectons (NCTs), which use synthetic polymers end-functionalized with supramolecular recognition groups capable of directing their assembly; programmable atom equivalents (PAEs) containing brushes of synthetic DNA that employ Watson–Crick base pairing to encode particle binding interactions; and cross-linkable nanoparticles (XNPs) that can both stabilize nanoparticles in solution and polymer matrices and subsequently form multivalent cross-links to strengthen polymer composites. We describe the formation of these brushes through “grafting-from” and “grafting-to” strategies and illustrate aspects that are important for future advancement. We also examine the new capabilities brushes provide, looking closely at dynamic polymer processes that provide control over the assembly state of particles. Finally, we provide a brief overview of the technological applications of nanoparticles with polymer brushes, focusing on the integration of nanoparticles into traditional materials and the processing of nanoparticles into bulk solids.
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- Award ID(s):
- 2204222
- PAR ID:
- 10496668
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- Accounts of Chemical Research
- Volume:
- 56
- Issue:
- 14
- ISSN:
- 0001-4842
- Page Range / eLocation ID:
- 1931 to 1941
- Subject(s) / Keyword(s):
- Ligands, Nanoparticles, Polymer brushes, Polymer particles, Polymers
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Bottlebrush polymers, macromolecules consisting of dense polymer side chains grafted from a central polymer backbone, have unique properties resulting from this well-defined molecular architecture. With the advent of controlled radical polymerization techniques, access to these architectures has become more readily available. However, synthetic challenges remain, including the need for intermediate purification, the use of toxic solvents, and challenges with achieving long bottlebrush architectures due to backbone entanglements. Herein, we report hybrid bonding bottlebrush polymers (systems integrating covalent and noncovalent bonding of structural units) consisting of poly(sodium 4-styrenesulfonate) (p(NaSS)) brushes grafted from a peptide amphiphile (PA) supramolecular polymer backbone. This was achieved using photoinitiated electron/energy transfer-reversible addition–fragmentation chain transfer (PET-RAFT) polymerization in water. The structure of the hybrid bonding bottlebrush architecture was characterized using cryogenic transmission electron microscopy, and its properties were probed using rheological measurements. We observed that hybrid bonding bottlebrush polymers were able to organize into block architectures containing domains with high brush grafting density and others with no observable brushes. This finding is possibly a result of dynamic behavior unique to supramolecular polymer backbones, enabling molecular exchange or translational diffusion of monomers along the length of the assemblies. The hybrid bottlebrush polymers exhibited higher solution viscosity at moderate shear, protected supramolecular polymer backbones from disassembly at high shear, and supported self-healing capabilities, depending on grafting densities. Our results demonstrate an opportunity for novel properties in easily synthesized bottlebrush polymer architectures built with supramolecular polymers that might be useful in biomedical applications or for aqueous lubrication.more » « less
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Abstract Modification of a surface with polymer brushes has emerged as an effective approach to tune the properties of a substrate. Brushes grown from an inimer‐containing cross‐linkable polymer coating provide significant advantages compared to other “grafting‐from” methods, such as improved stability, increased grafting density, and the potential to control the grafting density. So far, the inimer coating method has only been applied for surface‐initiated controlled radical polymerizations. In this work, an approach is presented for the fabrication of a stable cross‐linked ultra‐thin polymer coating containing hydroxyl groups which serve as initiating sites for surface‐initiated ring‐opening polymerization (SI‐ROP). The polymers used for the fabrication of the coatings consist of 2‐((tetrahydro‐2H‐pyran‐2‐yl)oxy)ethyl methacrylate (THPEMA), a small fraction of a cross‐linkable unit, and a diluent styrene. Three coatings with varying THPEMA and styrene content are fabricated, and poly(dimethyl siloxane) (PDMS) and poly(caprolactone) (PCL) brushes are grown by SI‐ROP of hexamethylcyclotrisiloxane (D3), and ε‐caprolactone respectively. The brushes are characterized by atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS), static contact angle measurements, ellipsometry and size exclusion chromatography (SEC). The results demonstrate a well‐controlled ROP of D3and ability to control grafting density by tuning the THPEMA content of the coatings.more » « less
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The adhesion of nanoparticles to lipid vesicles causes curvature deformations to the membrane to an extent determined by the competition between the adhesive interaction and the membrane’s elasticity. These deformations can extend over length scales larger than the size of a nanoparticle, leading to an effective membrane-curvature-mediated interaction between nanoparticles. Nanoparticles with uniform surfaces tend to aggregate into unidimensionally close-packed clusters at moderate adhesion strengths and endocytose at high adhesion strengths. Here, we show that the suppression of close-packed clustering and endocytosis can be achieved by the surface modification of the nanoparticles into Janus particles where a moiety of their surface is grafted with polymers under a good solvent condition. The osmotic pressure of the polymer brushes prevents membrane wrapping of the nanoparticles’ moieties that are grafted with polymers, thus suppressing their endocytosis. Furthermore, a repulsion between polymer brushes belonging to two nearby nanoparticles destabilizes the dimerization of the nanoparticles over a wide range of values of the polymers’ molecular weight and grafting density. This surface modification of nanoparticles should allow for reliable, non-close-packed, and tunable self-assemblies of nanoparticles.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.accounts.3c00160
