New approach for SANS measurement of micelle chain mixing during size and morphology transitions

Larison, Taylor; Pingali, Sai Venkatesh; Stefik, Morgan

doi:10.1039/d3sm00157a

Cited by 2 publications

(2 citation statements)

References 56 publications

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“…It is noted that a recently developed shifting reference relaxation function (SRR(t)) approach extends the simplicity of R(t) with added tolerance to size and morphology changes. 61 Separate measurements of EO-MA and EO-DMA micelles were most consistent with spherical micelles having a radius of ∼8.6 nm (Figure S7). Here, the analysis of SANS data with R(t) plots clearly shows distinct slopes, indicating that the initial rates are higher than the steady rates.…”

Section: ■ Results and Discussionmentioning

confidence: 58%

“…Comparison here of the quiescent and in situ ultrasonication SANS data also confirms that there is no detectable intensity change as a result of bubbles (Figure S10). It is noted that a recently developed shifting reference relaxation function (SRR( t )) approach extends the simplicity of R ( t ) with added tolerance to size and morphology changes . Separate measurements of EO-MA and EO-DMA micelles were most consistent with spherical micelles having a radius of ∼8.6 nm (Figure S7).…”

Section: Resultsmentioning

confidence: 91%

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Bimodal Rates for Cavitation-Induced Chain Exchange Between Micelles

Larison,

Williams,

Collins

et al. 2023

Macromolecules

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Ultrasonic cavitation temporarily activates chain exchange for otherwise kinetically trapped block polymer micelles. Initial studies of cavitation-induced exchange (CIE) examined dilute polymer concentrations (0.1–1.0 wt %) with low extents of mixing (R(t) of ∼0.9 or ∼10% mixed). This study examines CIE kinetics with in situ SANS measurements during continuous ultrasonication for extended timescales that reach deeper extents of mixing (R(t) of ∼0.6 or ∼40% mixed) with semidilute polymer concentrations (1.0–5.0 wt %). All these time-dependent measurements revealed two distinct mixing rates: a fast initial rate for ∼15 min followed by transition to a 10.8x slower steady rate corresponding to the transition from gas-bubbles to vapor-bubbles. The faster rate of chain exchange for gas-bubble cavitation further connects the CIE to surface area turnover as the rate-limiting step. Both regimes had exchange rates that were directly proportional to the polymer concentration without apparent steric hindrances, suggesting that neither gas-bubble nor vapor-bubble cavitation heat was rate-limiting.

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Section: ■ Results and Discussionmentioning

confidence: 58%

Section: Resultsmentioning

confidence: 91%

Bimodal Rates for Cavitation-Induced Chain Exchange Between Micelles

Larison,

Williams,

Collins

et al. 2023

Macromolecules

Self Cite

View full text Add to dashboard Cite

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Kinetics of Chain Exchange in Asymmetric ABA′ Triblock Polymer Micelles by Time-Resolved Small-Angle Neutron Scattering

Kim,

Wang,

White

et al. 2024

Macromolecules

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The effect of corona block asymmetry on chain exchange kinetics has been investigated using time-resolved smallangle neutron scattering (TR-SANS) with a series of AB di-and ABA′ triblock micelles composed of poly(ethylene-alt-propylene) (A) and polystyrene (B) block copolymers in squalane. The four copolymers maintain constant molecular weight and total block composition, but have different asymmetry ratios of the end blocks, denoted as SEP, EPSEP′-1, EPSEP′-2, and EPSEP. The TR-SANS results reveal a 10-fold acceleration in the chain exchange rate for asymmetric triblock copolymer micelles (EPSEP′-1 and EPSEP′-2) and a hundred-fold acceleration for symmetric triblock copolymers (EPSEP), compared to the SEP diblock copolymer. This enhanced exchange rate is primarily attributed to differences in the micelle structure associated with corona chain entropy during extraction, supported by calculations of grafting chain density and stretching of corona chains. Thus, this study demonstrates an interesting and significant role of block copolymer asymmetry in molecular exchange dynamics.

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New approach for SANS measurement of micelle chain mixing during size and morphology transitions

Abstract: Molecular exchange between micelles or other assemblies is measurable during size and morphology changes by combining appropriate time-resolved small-angle neutron scattering (TR-SANS) measurements with the SRR approach.

Cited by 2 publications

References 56 publications

Bimodal Rates for Cavitation-Induced Chain Exchange Between Micelles

Bimodal Rates for Cavitation-Induced Chain Exchange Between Micelles

Kinetics of Chain Exchange in Asymmetric ABA′ Triblock Polymer Micelles by Time-Resolved Small-Angle Neutron Scattering

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