Understanding the Ultrafast Crystallization Kinetics of Donor-Acceptor Semiconducting Polymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Physical Chemistry

Background:

• Donor-acceptor semiconducting polymers exhibit rapid crystallization kinetics at high temperatures (>300 °C), complicating traditional kinetic analysis.
• Existing experimental methods struggle to capture the subsecond crystallization timescales, limiting understanding of polymer solid-state microstructure.
• Investigating crystallization kinetics is crucial for controlling the properties of advanced semiconducting polymers.

Purpose of the Study:

• To develop and apply a novel experimental approach for analyzing fast isothermal crystallization kinetics in donor-acceptor semiconducting polymers.
• To introduce a modified Malkin model for accurately describing the complex crystallization behavior of these materials.
• To elucidate the relationship between crystallization kinetics, morphology, and nucleation mechanisms in advanced polymers.

Main Methods:

• Utilized single-step fast scanning calorimetry (FSC) to achieve subsecond resolution for isothermal crystallization studies.
• Applied a modified Malkin model to analyze the kinetic evolution of crystallization.
• Employed X-ray diffraction, melting analysis, and electron microscopy for morphological characterization.

Main Results:

• Successfully obtained reliable kinetic data for donor-acceptor polymers (PTQ10, D18) within tenths of a second using FSC.
• The modified Malkin model accurately captured the entire crystallization process, revealing two distinct regimes based on crystallization temperature.
• Identified different crystalline morphologies linked to crystallization kinetics, confirmed by multiple characterization techniques.
• Observed crystallization proceeding via rapid nanoscopic crystallite formation, governed by a dominant kinetic step, but deviating from classical nucleation behavior.

Conclusions:

• Fast scanning calorimetry (FSC) provides a powerful tool for studying rapid polymer crystallization kinetics.
• The modified Malkin model offers a robust framework for analyzing complex crystallization behavior and its link to morphology.
• The crystallization mechanism in these advanced polymers deviates from classical nucleation, suggesting unique self-nucleation processes.
• These findings establish a new paradigm for understanding and controlling the solid-state microstructure of semicrystalline polymers.