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Polymorphic Self-Poisoning in the Isothermal Crystallization of Thermoplastic Polyurethanes.
Zakarya Baouch1, Irene Guardincerri1, Katalee Jariyavidyanont2
1Department of Chemistry and Industrial Chemistry, University of Genoa, Via Dodecaneso 31, 16146 Genoa, Italy.
Macromolecules
|March 2, 2026
Summary
The crystallization kinetics of thermoplastic polyurethanes (TPUs) depend on hard segment content and polymorph competition. Low hard segment TPUs form only Form I, while higher content TPUs show complex kinetics due to competing Form I and Form II polymorphs.
Area of Science:
- Polymer Science
- Materials Science
- Crystallization Kinetics
Background:
- Thermoplastic polyurethanes (TPUs) are multiblock copolymers.
- Properties are strongly influenced by hard segment (HS) crystallization.
- HSs can form two polymorphs: Form I (kinetically favored) and Form II (thermodynamically stable).
Purpose of the Study:
- Investigate isothermal crystallization kinetics of TPUs with varying HS content (29-80 wt %).
- Explore the influence of HS content on polymorph formation and crystallization rates.
- Understand the relationship between polymorphic competition and kinetics.
Main Methods:
- Differential scanning calorimetry (DSC)
- Wide-angle X-ray diffraction (WAXD)
- Polarized light optical microscopy (PLOM)
- Fast scanning calorimetry (FSC)
Main Results:
- TPUs with low HS content (29-33 wt %) exclusively form Form I.
- TPUs with ≥50 wt % HS exhibit nonmonotonic crystallization rates with temperature.
- Polymorphic competition between Form I and Form II causes rate inversions, possibly due to self-poisoning.
Conclusions:
- Direct link established between polymorphic competition and crystallization kinetics in TPUs.
- Findings provide insights into structure formation in TPUs.
- Offers strategies for tailoring TPU properties through controlled crystallization.
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