Size evolution of highly amphiphilic macromolecular solution assemblies via a distinct bimodal pathway

Kelley, Elizabeth G.; Murphy, R.A.; Seppala, Jonathan E.; Smart, Thomas P.; Hann, Sarah D.; Sullivan, Millicent O.; Epps, Thomas H.

doi:10.1038/ncomms4599

Cited by 74 publications

(82 citation statements)

References 64 publications

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“…Cryo-TEM experiments further demonstrated that mechanical agitation (stirring), in addition to TMB, is a requirement for producing these broadened micelle size distributions (Fig. 3e, j, o ), consistent with recent observations of complex polymer micelle size distributions in the presence of a co-solvent and solution agitation 34 . Associated structural transitions are illustrated schematically by the micelle packings in Fig.…”

Section: Resultssupporting

confidence: 89%

Formation pathways of mesoporous silica nanoparticles with dodecagonal tiling

Sun

Kao

et al. 2017

Nat Commun

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Considerable progress in the fabrication of quasicrystals demonstrates that they can be realized in a broad range of materials. However, the development of chemistries enabling direct experimental observation of early quasicrystal growth pathways remains challenging. Here, we report the synthesis of four surfactant-directed mesoporous silica nanoparticle structures, including dodecagonal quasicrystalline nanoparticles, as a function of micelle pore expander concentration or stirring rate. We demonstrate that the early formation stages of dodecagonal quasicrystalline mesoporous silica nanoparticles can be preserved, where precise control of mesoporous silica nanoparticle size down to <30 nm facilitates comparison between mesoporous silica nanoparticles and simulated single-particle growth trajectories beginning with a single tiling unit. Our results reveal details of the building block size distributions during early growth and how they promote quasicrystal formation. This work identifies simple synthetic parameters, such as stirring rate, that may be exploited to design other quasicrystal-forming self-assembly chemistries and processes.

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Section: Resultssupporting

confidence: 89%

Formation pathways of mesoporous silica nanoparticles with dodecagonal tiling

Sun

Kao

et al. 2017

Nat Commun

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“…79 2) The large hydrophilic-hydrophobic contrast represented by the high Flory-Huggins interaction parameter drives phase separation of the blocks and enables modulation of the reorganization kinetics based upon the presented solution conditions. [80][81][82][83] 3) The polymer is simple to synthesize in diverse laboratory settings by atom transfer radical polymerization (ATRP) using a chain extension from commercial PEO homopolymers. Different size PEO macroinitiators were synthesized by the esterification of commercial poly(ethylene glycol)methyl ether with 2-bromopropionic acid ( Figure S1).…”

Section: Resultsmentioning

confidence: 99%

Ordered Mesoporous to Macroporous Oxides with Tunable Isomorphic Architectures: Solution Criteria for Persistent Micelle Templates

et al. 2016

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Porous and nanoscale architectures of inorganic materials have become crucial for a range of energy and catalysis applications, where the ability to control the morphology largely determines the transport characteristics and device performance. Despite the availability of a range of block copolymer self-assembly methods, the conditions for tuning the key architectural features such as the inorganic wall-thickness have remained elusive. Towards this end we have developed solution processing guidelines that enable isomorphic nanostructures with tunable wall-thickness. A new poly(ethylene oxide-b-hexyl acrylate) (PEOb-PHA) structure directing agent (SDA) was used to demonstrate the key solution design criteria. Specifically, the use of a polymer with a high Flory-Huggins effective interaction parameter, χ, and appropriate solution conditions leads to the kinetic entrapment of persistent micelle templates (PMT) for tunable isomorphic architectures. Solubility parameters are used to predict conditions for maintaining persistent micelle sizes despite changing equilibrium conditions. Here the use of different inorganic loadings controls the inorganic wall-thickness with constant pore size. This versatile method enabled a record 55 nm oxide wall-thickness from micelle coassembly as well as the seamless transition from mesoporous materials to macroporous materials by varying the polymer molar mass and solution conditions. The processing guidelines are generalizable and were elaborated with three inorganic systems, including Nb 2 O 5 , WO 3 , and SiO 2 that were thermally stable to 600 o C for access to crystalline materials. access to extensive pore size regimes that seamlessly span from mesopores to macropores. This concept is demonstrated with a new PEO-b-PHA SDA. The use of a polymer with sufficiently high Flory-Huggins interaction parameter is needed to inhibit micelle re-equilibration that would otherwise change the final pore size with different inorganic loadings. Both micelle fusion-fission and unimer expulsion-insertion reactions may be slowed with appropriate solution conditions that inhibit micelle changes. 68-72 The demonstrated broad range of tunable pore sizes fills the gap typically found between block copolymer approaches and colloidal approaches. The resulting materials were stable to high temperatures and enabled the formation of multiple crystalline oxide frameworks. Experimental Methods Reagents: Anhydrous, inhibitor free THF (>99.9%, Aldrich), Niobium (V) ethoxide (99.9%, Fisher) and Tungsten (VI) chloride (99.9%, Acros) were stored inside a glove box and used as received. Concentrated hydrochloric acid (37 wt% ACS grade, VWR) and Tetraethoxysilane (98%, Alfa Aesar) were used as received. Poly(ethylene glycol) methyl ether (M n 20, 000 g mol-1 , Aldrich) was dried by azeotropic distillation with toluene before use.

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“…14–19 However, recent experiments have indicated that, even near equilibrium, fusion and fission processes may still occur. 20–21 Fusion of micelles is also observed under flow conditions. 22 Far from equilibrium, theoretical work by Semenov and coworkers suggest that insertion and expulsion are prevalent; 23 however, Dormidontova et al have proposed that fusion and fission processes dominate.…”

Section: Introductionmentioning

confidence: 82%

Fluorophore exchange kinetics in block copolymer micelles with varying solvent–fluorophore and solvent–polymer interactions

et al. 2016

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Fluorescence spectroscopy was employed to characterize the kinetics of guest exchange in diblock copolymer micelles composed of poly(ethylene oxide-b-ε-caprolactone) (PEO-PCL) diblock copolymers in water/tetrahydrofuran (THF) mixtures which encapsulated fluorophores. The solvent composition (THF content) of the micelle solution was varied as a means of modulating the strength of interactions between the fluorophore and solvent as well as between the micelle core and solvent. A donor-acceptor fluorophore pair was employed consisting of 3,3′-dioctadecyloxacarbocyanine perchlorate (DiO, the donor) and 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI, the acceptor). Through the process of Förster resonance energy transfer (FRET), energy was transferred from the donor to acceptor when the fluorophores were in close proximity. A micelle solution containing DiO was mixed with a micelle solution containing DiI at t=0, and the emission spectra of the mixed solution were monitored over time (at an excitation wavelength optimized for the donor). In micelle solutions containing 5 and 10 vol% THF in the bulk solvent, an increase in the acceptor peak intensity maximum occurred over time in the post-mixed solution, accompanied by a decrease in the donor peak intensity maximum, indicating the presence of energy transfer from the donor to the acceptor. At long times, the FRET ratios (acceptor peak intensity divided by the sum of the acceptor and donor peak intensities) were indistinguishable from that determined from pre-mixed micelle solutions of the same THF content (in pre-mixed solutions, DiO and DiI were encapsulated within the same micelle cores). In the micelle solution containing 20 vol% THF, the fluorophore exchange process occurred too quickly to be observed (the FRET ratios measured from the solutions mixed at t=0 were commensurate to that measured from the pre-mixed solution). A time constant describing the guest exchange process was extracted from the time-dependence of the FRET ratio through fit of an exponential decay. An increase in the THF content in the micelle solution resulted in a decrease in the time constant, and the time constant varied over five orders of magnitude as the THF content was varied from 5–20 vol%.

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Size evolution of highly amphiphilic macromolecular solution assemblies via a distinct bimodal pathway

Cited by 74 publications

References 64 publications

Formation pathways of mesoporous silica nanoparticles with dodecagonal tiling

Formation pathways of mesoporous silica nanoparticles with dodecagonal tiling

Ordered Mesoporous to Macroporous Oxides with Tunable Isomorphic Architectures: Solution Criteria for Persistent Micelle Templates

Fluorophore exchange kinetics in block copolymer micelles with varying solvent–fluorophore and solvent–polymer interactions

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