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Antiplasticization and phase behavior in phase-separated modified starch-sucrose blends: A positron lifetime and
Francesca Martini1, David J Hughes2, Gabriela Badolato Bönisch3
1Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Moruzzi 13, 56124, Pisa, Italy.
Carbohydrate Polymers
|October 14, 2020
Summary
Sucrose partially separates from hydrophobically modified starch (HMS) in ternary blends, creating nanoscale structures. This unique organization influences blend dynamics and antiplasticization effects.
Area of Science:
- Materials Science
- Polymer Chemistry
- Food Science
Background:
- Understanding phase separation in ternary blends is crucial for controlling material properties.
- Hydrophobically modified starch (HMS) and sucrose mixtures are relevant in food and material applications.
- Nanoscale organization significantly impacts blend dynamics and macroscopic behavior.
Purpose of the Study:
- To investigate the interactions, organization, and dynamics within phase-separated ternary blends of HMS, sucrose, and water.
- To elucidate the role of sucrose in the phase behavior and antiplasticization of HMS.
- To characterize the nanoscale structure of the phase-separated domains.
Main Methods:
- Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, including 1H T1 relaxation and 13C selective experiments.
- Positron Annihilation Lifetime Spectroscopy (PALS) to probe free volume and molecular packing.
- 1H spin diffusion experiments to assess nanoscale phase separation.
Main Results:
- Evidence of antiplasticization of HMS by sucrose was observed using PALS and 1H NMR T1.
- Partial phase separation between HMS and sucrose was confirmed, with significant molecular contact.
- Sucrose migration from HMS-rich domains occurred at temperatures between the glass transition temperatures (Tg).
- 1H spin diffusion indicated nanoscale phase separation (nanometric scale).
Conclusions:
- The nanoscale structure of HMS-rich domains facilitates intimate molecular contact between phases.
- Partial phase separation and nanoscale organization explain the unusual dynamic behavior observed in the blends.
- Sucrose acts as an antiplasticizer for HMS, influencing blend properties through molecular interactions and phase behavior.
Keywords:
(1)H relaxation times(13)C CP-MASAmorphous phase separationAntiplasticizationFree volumeOSA-starchPlasticizationPositron annihilationSucroseMore Related Videos
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