Combined Small-Angle Scattering for Characterization of Hierarchically Structured Polymer Systems over Nano-to-Micron Meter

Beaucage, Gregory

doi:10.1016/b978-0-444-53349-4.00032-7

Cited by 32 publications

(23 citation statements)

References 28 publications

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“…S3) finds the configurations of the assembly in THF to be random coils, as indicated by an ∼ Q −2 power-law dependence of the SANS in the mid-Q region (SI Appendix, Fig. S3): The Q −2 scaling is consistent with a Gaussian fractal chain, equivalent to a random coil in θ-solvent conditions (28), although the precise origin of the scattering cannot be unequivocally inferred from the experiments alone. The assembly revealed by SANS can thus be considered as rodlike aggregates of entangled lignin molecules (SI Appendix, Fig.…”

Section: Resultsmentioning

confidence: 97%

Deconstruction of biomass enabled by local demixing of cosolvents at cellulose and lignin surfaces

Pingali

Smith

Liu

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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A particularly promising approach to deconstructing and fractionating lignocellulosic biomass to produce green renewable fuels and high-value chemicals pretreats the biomass with organic solvents in aqueous solution. Here, neutron scattering and molecular-dynamics simulations reveal the temperature-dependent morphological changes in poplar wood biomass during tetrahydrofuran (THF):water pretreatment and provide a mechanism by which the solvent components drive efficient biomass breakdown. Whereas lignin dissociates over a wide temperature range (>25 °C) cellulose disruption occurs only above 150 °C. Neutron scattering with contrast variation provides direct evidence for the formation of THF-rich nanoclusters (Rg ∼ 0.5 nm) on the nonpolar cellulose surfaces and on hydrophobic lignin, and equivalent water-rich nanoclusters on polar cellulose surfaces. The disassembly of the amphiphilic biomass is thus enabled through the local demixing of highly functional cosolvents, THF and water, which preferentially solvate specific biomass surfaces so as to match the local solute polarity. A multiscale description of the efficiency of THF:water pretreatment is provided: matching polarity at the atomic scale prevents lignin aggregation and disrupts cellulose, leading to improvements in deconstruction at the macroscopic scale.

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Section: Resultsmentioning

confidence: 97%

Deconstruction of biomass enabled by local demixing of cosolvents at cellulose and lignin surfaces

Pingali

Smith

Liu

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…In order to go beyond the simple power-law description of the intensity spectra I(q) proposed in the main text, we model the USAXS data obtained on the 3 % vol. carbon black gel with the Beaucage model [77]. Originally designed for polymeric mass fractals [78,79], this model uses a "unified" function that interpolates between a Guinier regime at low q and a power-law Porod scaling at large q.…”

Section: Analysis Of Usaxs Measurementsmentioning

confidence: 99%

Rheoacoustic Gels: Tuning Mechanical and Flow Properties of Colloidal Gels with Ultrasonic Vibrations

et al. 2020

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Colloidal gels, where nanoscale particles aggregate into an elastic yet fragile network, are at the heart of materials that combine specific optical, electrical and mechanical properties. Tailoring the viscoelastic features of colloidal gels in real-time thanks to an external stimulus currently appears as a major challenge in the design of "smart" soft materials. Here we show that ultrasound allows one to achieve this goal in well-controlled conditions. By using a combination of rheological and structural characterization, we evidence and quantify a strong softening in three widely different colloidal gels submitted to ultrasonic vibrations (with submicron amplitude and frequency 20-500 kHz). This softening is attributed to the fragmentation of the gel network into large clusters that may or may not fully re-aggregate once ultrasound is turned off depending on the acoustic intensity. Ultrasound is further shown to dramatically decrease the gel yield stress and accelerate shear-induced fluidization, thus opening the way to a full control of elastic and flow properties by ultrasonic vibrations.Colloidal gels constitute a class soft materials with a huge spectrum of applications, ranging from paints, oil extraction and construction to pharmaceuticals and food products [1,2]. These gels are typically formed from the aggregation of attractive nanoscale particles that arrange into a space-spanning network which strength provides the system with elastic properties at rest. The particle network is, however, fragile enough that rather weak external forces disrupt the gel structure and induce flow above a critical yield strain or stress [3]. Such unique mechanical and flow properties are key to applications that require an interplay between solid and fluid behaviour, including cement placement, ink-jet printing or flow-cell batteries. In this context, decades of research have investigated the influence of physico-chemical parameters such as temperature, pH and ionic strength on the aggregation of attractive particles into colloidal gels [4][5][6][7][8][9]. While electrostatic repulsion, van der Waals attraction and steric interaction, combined in the well-known DLVO interparticle potential, generically lead to the formation of fractal networks through diffusion-or reaction-limited cluster aggregation, additional chemical effects such as hydration layers or particle bridging generate a wealth of more complex gel microstructures [10]. In the quest of smart, responsive materials, tuning the gel architecture in realtime and reversibly is a key challenge. However, playing on the above physico-chemical parameters turns out to be difficult, if not impossible when the chemistry of the material is strongly constrained. Electro-or magnetorheological materials allow for such tuning through the use of electrical and magnetic fields [11][12][13][14]. Yet, applications are obviously restricted to materials with specific compositions [15][16][17].The exquisite sensitivity of colloidal gels to external mechanical perturbations provides an...

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“…The nanocomposites with higher SiO 2 content (EAS3 and EAS5) possess an additional knee at higher q values (between 0.1 and 0.2 Å −1 ) that can be attributed to inorganic domains with higher electron density [30]. These features in the scattering may be attributed to inorganic nanoparticles arranged in hierarchical structures at different size scales [31]. The scattering data for all the samples were analyzed using modelindependent methods.…”

Section: Structure and Morphology Of The Nanocompositesmentioning

confidence: 99%

In situ synthesis of epoxy nanocomposites with hierarchical surface-modified SiO2 clusters

Adnan

Tveten

Miranti

et al. 2020

J Sol-Gel Sci Technol

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Polymer nanocomposites are often produced using in situ approaches where an inorganic filler (as the dispersed phase) is synthesized directly in an organic matrix. Such an approach generally leads to improved dispersion and reduced agglomeration of the filler material. Epoxy-based nanocomposites have demonstrated promising properties for application as high-voltage insulation materials. In this work, a sol-gel based method has been adapted to synthesize surface-functionalized SiO 2 in situ in epoxy. The synthesized SiO 2 moieties were dispersed in clusters of 10-80 nm, and formed chemical bonds with the epoxy monomers via a silane coupling agent. Raman spectra show the formation of four-membered D 1 rings, which may be part of a cage-like structure similar to that of polyhedral oligomeric silsesquioxanes (POSS). SAXS measurements indicate that the SiO 2 clusters consist of a hierarchical structure with an increasing fractal dimension with increasing SiO 2 content. The nanocomposites displayed improved thermal stability, while the glass transition behavior varied depending on the structure and content of the SiO 2 moieties. While the relative permittivity showed no significant changes from that of pure epoxy, the onset of the dielectric relaxation changed with the SiO 2 structure and content, similar to the behavior observed for the glass transition.

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Combined Small-Angle Scattering for Characterization of Hierarchically Structured Polymer Systems over Nano-to-Micron Meter

Cited by 32 publications

References 28 publications

Deconstruction of biomass enabled by local demixing of cosolvents at cellulose and lignin surfaces

Deconstruction of biomass enabled by local demixing of cosolvents at cellulose and lignin surfaces

Rheoacoustic Gels: Tuning Mechanical and Flow Properties of Colloidal Gels with Ultrasonic Vibrations

In situ synthesis of epoxy nanocomposites with hierarchical surface-modified SiO2 clusters

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