Dynamics of Polymerization and Gelation in Epoxy Nanocomposites <i>via</i> X-ray Photon Correlation Spectroscopy

Trigg, Edward B.; Wiegart, Lutz; Fluerasu, Andrei; Koerner, Hilmar

doi:10.1021/acs.macromol.1c00727

Cited by 13 publications

(10 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Many strategies exist to manipulate these interactions, e.g., polymer grafts, − external fields, − and polymer crystallization. − In addition to these factors, we require an understanding of NP dynamics in polymer melts since NP dispersion in many instances can be far from equilibrium and, in that case, determined by local NP (and chain) dynamics. To gain critical insights into this topic, we use X-ray photon correlation spectroscopy (XPCS), a technique that has examined NP dynamics across a variety of PNC systems, − to probe the dynamics of silica NPs in entangled ( M n / M e ∼ 2.5–20) poly(ethylene oxide) (PEO) melts. We are particularly interested in NP diffusion in the melt state, and how it relates to crystallization-induced NP ordering when the nanocomposite is cooled to temperatures below the polymer’s melting point.…”

Section: Introductionmentioning

confidence: 99%

Nanoparticle Diffusion in Miscible Polymer Nanocomposite Melts

et al. 2023

View full text Add to dashboard Cite

X-ray photon correlation spectroscopy measurements were used to quantify the dynamics of bare and bimodal grafted silica nanoparticles mixed with PEO melts of different molecular weights. In dilute polymer nanocomposite (PNC) samples, we find diffusive NP behavior as described by the Stokes–Einstein relationship so long as the adsorbed PEO polymer layer is taken into account in determining both the effective NP size and its role on composite viscosity. The size of this bound layer was found to be approximately 2R g, where R g is the chain radius of gyration. We also expanded our system to investigate how the dynamics of grafted NPs differ from bare NPs with an adsorbed layer. We showed that the dynamics again can be determined by an effective NP radius at a scale smaller than the effective interparticle spacing; however, at larger length scales, the morphology and grafting parameters play a major role in the system dynamics. These results allow us to quantify NP ordering driven by polymer crystallization. It has previously been speculated that behavior is controlled by the relative ratio of time scale of crystal growth and the diffusive time scale of the NPs, a Peclet number. When the former time scale is longer, then the NPs are expected to be segregated into the interlamellar amorphous zones, while the NPs are too slow to be reorganized in the opposite case. We show here that this conjecture is quantitatively correct and the demarcation in behavior occurs for Pe = 1. Thus, we provide a way to estimate a critical spherulite growth rate for any semicrystalline PNC, at which a given NP can be ordered. Together, the results of this study permit us to tunably design PNCs through directed dispersion of NPs in a polymer matrix.

show abstract

Section: Introductionmentioning

confidence: 99%

Nanoparticle Diffusion in Miscible Polymer Nanocomposite Melts

et al. 2023

View full text Add to dashboard Cite

show abstract

“…At early times, the conversion is nonzero, starting near α ≈ 0.2 at the beginning of the isothermal cure process. This is due to unavoidable curing that occurs during the ramp from room temperature to 100 °C, as confirmed by DSC (see Figure S2 in the Supporting Information) and noted by previous researchers . The conversion profile exhibits a sigmoidal shape on a logarithmic time scale with conversion dynamics slowing down after 3000 s as the reaction nears completion.…”

Section: Results and Discussionmentioning

confidence: 99%

Evaluating Models That Predict Epoxy Conversion Using Rheological Properties

Romberg,

Roberts,

Snyder

et al. 2024

ACS Appl. Polym. Mater.

View full text Add to dashboard Cite

Simultaneous rheology and conversion measurements of neat and composite epoxy resins reveal that conventional models neither accurately nor fully describe the relationship between rheology and conversion. We find that models predicting thermoset conversion based on mixing rules of rheological properties are quantitatively inaccurate and do not account for chemical gelation. Models based on percolation theory and the divergence of the viscosity at the gel point are more accurate but valid only before the gel point. Here, we propose the use of the generalized effective medium (GEM) model, which incorporates the divergence of the rheological properties on both sides of the critical gel point. We show that the GEM model works well for both neat resins and filled systems, and the resulting parameters estimate the gel point and scaling behavior on either side of the sol−gel transition.

show abstract

“…Real-space observation, such as electron microscopy, − has revealed the possibility of an interlocking or anchoring effect, , as described by the mechanical theory. Depth profiling techniques such as dynamic secondary ion mass spectroscopy (DSIMS), , X-ray/neutron reflectivity measurements, − and confocal Raman scattering have enabled us to examine the interfacial layer formed by the interdiffusion of polymers, of which the thickness directly affects the adhesion strength. − However, there seems to be very limited exploration of experimental approaches to electronic theory. X-ray photoelectron spectroscopy measurements with Ar gas cluster ion beam sputtering and transmission electron microscopy with electron energy-loss spectroscopy are plausible techniques for this purpose.…”

Section: Introductionmentioning

confidence: 99%

Electronic Interaction of Epoxy Resin with Copper at the Adhered Interface

Saeki,

Kawaguchi,

Tsuji

et al. 2024

Langmuir

View full text Add to dashboard Cite

A better understanding of the aggregation states of adhesive molecules in the interfacial region with an adherend is crucial for controlling the adhesion strength and is of great inherent academic interest. The adhesion mechanism has been described through four theories: adsorption, mechanical, diffusion, and electronic. While interfacial characterization techniques have been developed to validate the aforementioned theories, that related to the electronic theory has not yet been thoroughly studied. We here directly detected the electronic interaction between a commonly used thermosetting adhesive, cured epoxy of diglycidyl ether of bisphenol A (DGEBA) and 4,4′-diaminodiphenylmethane (DDM), and copper (Cu). This study used a combination of density functional theory (DFT) calculations and femtosecond transient absorption spectroscopic (TAS) measurements as this epoxy adhesive-Cu pairing is extensively used in electronic device packaging. The DFT calculations predicted that π electrons in a DDM molecule adsorbed onto the Cu surface flowed out onto the Cu surface, resulting in a positive charge on the DDM. TAS measurements for the Cu/epoxy multilayer film, a model sample containing many metal/adhesive interfaces, revealed that the electronic states of excited DDM moieties at the Cu interface were different from those in the bulk region. These results were in good accordance with the prediction by DFT calculations. Thus, it can be concluded that TAS is applicable to characterize the electronic interaction of adhesives with metal adherends in a nondestructive manner.

show abstract

Dynamics of Polymerization and Gelation in Epoxy Nanocomposites via X-ray Photon Correlation Spectroscopy

Cited by 13 publications

References 47 publications

Nanoparticle Diffusion in Miscible Polymer Nanocomposite Melts

Nanoparticle Diffusion in Miscible Polymer Nanocomposite Melts

Evaluating Models That Predict Epoxy Conversion Using Rheological Properties

Electronic Interaction of Epoxy Resin with Copper at the Adhered Interface

Contact Info

Product

Resources

About