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Williams ER, Ruff CX, Stefik M. Unimer suppression enables supersaturated homopolymer swollen micelles with long-term stability after glassy entrapment. Soft Matter 2024; 20:2288-2300. [PMID: 38358107 DOI: 10.1039/d3sm01754k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
Micelle sizes are critical for a range of applications where the simple ability to adjust and lock in specific stable sizes has remained largely elusive. While micelle swelling agents are well-known, their dynamic re-equilibration in solution implies limited stability. Here, a non-equilibrium processing sequence is studied where supersaturated homopolymer swelling is combined with glassy-core ("persistent") micelles. This path-dependent process was found to sensitively depend on unimer concentration as revealed by DLS, SAXS, and TEM analysis. Here, lower-selectivity solvent combinations led to the formation of unimer-homopolymer aggregates and eventual precipitation, reminiscent of anomalous micellization. In contrast, higher-selectivity solvents enabled supersaturated homopolymer loadings favored by rapid homopolymer insertion. The demonstrated ∼40-130 nm core-size tuning exceeded prior equilibrium demonstrations and subsequent core-vitrification enabled size persistence beyond 6 months. Lastly, the linear change in micelle diameter with homopolymer addition was found to correlate with a plateau in the interfacial area per copolymer chain.
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Affiliation(s)
- Eric R Williams
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, 29208.
| | - Christian X Ruff
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, 29208.
| | - Morgan Stefik
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, 29208.
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Jara Fornerod M, Alvarez-Fernandez A, Williams ER, Skoda MWA, Prieto-Simon B, Voelcker NH, Stefik M, Coppens MO, Guldin S. Enhanced Structural Control of Soft-Templated Mesoporous Inorganic Thin Films by Inert Processing Conditions. ACS Appl Mater Interfaces 2022; 14:56143-56155. [PMID: 36503231 PMCID: PMC9782354 DOI: 10.1021/acsami.2c18090] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
Mesoporous thin films are widely used for applications in need of high surface area and efficient mass and charge transport properties. A well-established fabrication process involves the supramolecular assembly of organic molecules (e.g., block copolymers and surfactants) with inorganic materials obtained by sol-gel chemistry. Typically, subsequent calcination in air removes the organic template and reveals the porous inorganic network. A significant challenge for such coatings is the anisotropic shrinkage due to the volume contraction related to solvent evaporation, inorganic condensation, and template removal, affecting the final porosity as well as pore shape, size, arrangement, and accessibility. Here, we show that a two-step calcination process, composed of high-temperature treatment in argon followed by air calcination, is an effective fabrication strategy to reduce film contraction and enhance structural control of mesoporous thin films. Crucially, the formation of a transient carbonaceous scaffold enables the inorganic matrix to fully condense before template removal. The resulting mesoporous films retain a higher porosity as well as bigger pores with extended porous order. Such films present favorable characteristics for mass transport of large molecules. This is demonstrated for lysozyme adsorption into the mesoporous thin films as an example of enzyme storage.
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Affiliation(s)
| | - Alberto Alvarez-Fernandez
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Eric R. Williams
- Department
of Chemistry and Biochemistry, University
of South Carolina, Columbia, South Carolina 29208, United States
| | - Maximilian W. A. Skoda
- ISIS
Pulsed Neutron and Muon Source, Rutherford
Appleton Laboratory, Harwell, Oxfordshire OX11 OQX, U.K.
| | - Beatriz Prieto-Simon
- Department
of Electronic Engineering, Universitat Rovira
i Virgili, 43007 Tarragona, Spain
- ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Nicolas H. Voelcker
- Monash Institute
of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
- Melbourne
Centre for Nanofabrication, Victorian Node
of the Australian National Fabrication Facility, Clayton, Victoria 3168, Australia
| | - Morgan Stefik
- Department
of Chemistry and Biochemistry, University
of South Carolina, Columbia, South Carolina 29208, United States
| | - Marc-Olivier Coppens
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
- Centre
for Nature Inspired Engineering, University
College London, Torrington
Place, London WC1E 7JE, U.K.
| | - Stefan Guldin
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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Williams ER, van den Bergh W, Stefik M. High- χ, low- N micelles from partially perfluorinated block polymers. Soft Matter 2022; 18:7917-7930. [PMID: 36017726 DOI: 10.1039/d2sm00513a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Kinetically trapped ("persistent") micelles enable emerging applications requiring a constant core diameter. Preserving a χN barrier to chain exchange with low-N requires a commensurately higher χcore-solvent for micelle persistence. Low-N, high-χ micelles containing fluorophobic interactions were studied using poly(ethylene oxide-b-perfluorooctyl acrylate)s (O45FX, x = 8, 11) in methanolic solutions. DLS analysis of micelles revealed chain exchange only for O45F8 while SAXS analysis suggested elongated core block conformations commensurate with the contour lengths. Micelle chain exchange from solution perturbations were examined by characterizing their behavior as templates for inorganic materials via SAXS and SEM. In contrast to the F8 analog, the larger χN barrier for the O45F11 enabled persistent micelle behavior in both thin films and bulk samples despite the low Tg micelle core. Careful measures of micelle core diameters and pore sizes revealed that the nanoparticle distribution extended through the corona and 0.52 ± 0.15 nm into the core-corona interface, highlighting thermodynamics favoring both locations simultaneously.
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Affiliation(s)
- Eric R Williams
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA.
| | - Wessel van den Bergh
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA.
| | - Morgan Stefik
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208, USA.
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van den Bergh W, Williams ER, Vest NA, Chiang PH, Stefik M. Mesoporous TiO 2 Microparticles with Tailored Surfaces, Pores, Walls, and Particle Dimensions Using Persistent Micelle Templates. Langmuir 2021; 37:12874-12886. [PMID: 34617769 DOI: 10.1021/acs.langmuir.1c01865] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Mesoporous microparticles are an attractive platform to deploy high-surface-area nanomaterials in a convenient particulate form that is broadly compatible with diverse device manufacturing methods. The applications for mesoporous microparticles are numerous, spanning the gamut from drug delivery to catalysis and energy storage. For most applications, the performance of the resulting materials depends upon the architectural dimensions including the mesopore size, wall thickness, and microparticle size, yet a synthetic method to control all these parameters has remained elusive. Furthermore, some mesoporous microparticle reports noted a surface skin layer which has not been tuned before despite the important effect of such a skin layer upon transport/encapsulation. In the present study, material precursors and block polymer micelles are combined to yield mesoporous materials in a microparticle format due to phase separation from a homopolymer matrix. The skin layer thickness was kinetically controlled where a layer integration via diffusion (LID) model explains its production and dissipation. Furthermore, the independent tuning of pore size and wall thickness for mesoporous microparticles is shown for the first time using persistent micelle templates (PMT). Last, the kinetic effects of numerous processing parameters upon the microparticle size are shown.
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Affiliation(s)
- Wessel van den Bergh
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Eric R Williams
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Natalie Alicia Vest
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Pei-Hua Chiang
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Morgan Stefik
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
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Larison T, Stefik M. Persistent Micelle Corona Chemistry Enables Constant Micelle Core Size with Independent Control of Functionality and Polyelectrolyte Response. Langmuir 2021; 37:9817-9825. [PMID: 34355919 DOI: 10.1021/acs.langmuir.1c01384] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Polymer micelles have found significant uses in areas such as drug/gene delivery, medical imaging, and as templates for nanomaterials. For many of these applications, the micelle performance depends on its size and chemical functionalization. To date, however, these parameters have often been fundamentally coupled since the equilibrium size of a micelle is a function of the chemical composition in addition to other parameters. Here, we demonstrate a novel processing pathway allowing for the chemical modification to the corona of kinetically trapped "persistent" polymer micelles, termed Persistent Micelle Corona Chemistry (PMCC). Judicious planning is crucial to this size-controlled functionalization where each step requires all reagents and polymer blocks to be compatible with (1) the desired chemistry, (2) micelle persistency, and (3) micelle dispersion. A desired functionalization can be implemented with PMCC by pairing the synthetic planning with polymer solubility databases. Specifically, poly(cyclohexyl methacrylate-b-(diethoxyphosphoryl)methyl methacrylate) (PCHMA-b-PDEPMMA) was prepared to combine a glassy-core block (PCHMA) for kinetic control with a block (PDEPMMA) that is able to be hydrolyzed to yield acid groups. The processing sequence determines the resulting micelle size distribution where the hydrolyzed-then-micellized sequence yields widely varying micelle dimensions due to equilibration. In contrast, the micellized-then-hydrolyzed sequence maintains kinetically trapped micelles throughout the PMCC process. Statistically significant transmission electron microscopy (TEM) measurements demonstrate that PMCC uniquely enables this functionalization with constant average micelle core dimensions. Furthermore, these kinetically trapped micelles also subsequently maintain constant micelle core size when modifying the Coulombic interactions of the micelle corona via pH changes.
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Affiliation(s)
- Taylor Larison
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
| | - Morgan Stefik
- Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, United States
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Abstract
The combination of precision control with wide tunability remains a challenge for the fabrication of porous nanomaterials suitable for studies of nanostructure-behavior relationships. Polymer micelle templates broadly enable porous materials, however micelle equilibration hampers independent pore and wall size control. Persistent micelle templates (PMT) have emerged as a kinetic controlled platform that uniquely decouples the control of pore and wall dimensions. Here, chain exchange is inhibited to preserve a constant template dimension (pore size) despite the shifting equilibrium while materials are added between micelles. Early PMT demonstrations were synthesis intensive with limited 1-1.3× pore size tuning for a given polymer. Here we demonstrate PMT swelling with homopolymer enables 1-3.2× (13.3-41.9 nm) pore size variation while maintaining a monomodal distribution with up to 250 wt% homopolymer, considerably higher than the ∼90 wt% limit found for equilibrating micelles. These swollen PMTs enabled nanomaterial series with constant pore size and precision varied wall-thickness. Kinetic size control here is unexpected since the homopolymer undergoes dynamic exchange between micelles. The solvent selection influenced the time window before homopolymer phase separation, highlighting the importance of considering homopolymer-solvent interactions. This is the first PMT demonstration with wide variation of both the pore and wall dimensions using a single block polymer. Lastly this approach was extended to a 72 kg mol-1 block polymer to enable a wide 50-290 nm range of tunable macropores. Here the use of just two different block polymers and one homopolymer enabled wide ranging pore sizes spanning from 13.3-290 nm (1-22×).
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Affiliation(s)
- Amrita Sarkar
- Department of Chemistry & Biochemistry, University of South Carolina, Columbia, SC, USA.
| | - Akshay Thyagarajan
- Department of Chemistry & Biochemistry, University of South Carolina, Columbia, SC, USA.
| | - August Cole
- Department of Chemistry & Biochemistry, University of South Carolina, Columbia, SC, USA.
| | - Morgan Stefik
- Department of Chemistry & Biochemistry, University of South Carolina, Columbia, SC, USA.
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