Cross-Nucleation between Polymorphs: Quantitative Modeling of Kinetics and Morphology

Area of Science:

• Crystallization science
• Materials science
• Polymer science

Background:

• Cross-nucleation, the growth of one polymorph on another, is primarily described phenomenologically.
• Recent quantitative studies are emerging for specific systems.
• Understanding cross-nucleation is crucial for controlling material properties.

Purpose of the Study:

• To develop a model framework for cross-nucleation on a spherulitic seed-surface geometry.
• To analyze the kinetic competition between seed growth and cross-nucleus formation.
• To investigate the temperature dependency of cross-nucleation in isotactic polypropylene.

Main Methods:

• Proposed a model incorporating tangential growth rate of the daughter polymorph.
• Applied the model to describe experimental data for cross-nuclei formation.
• Observed and analyzed the kinetic competition between α- and β-phases of isotactic polypropylene.

Main Results:

• The model successfully describes experimental data for cross-nuclei formation on crystal periphery.
• The model's accuracy relies on a single parameter: the cross-nucleation rate.
• A significant temperature dependency was observed in the kinetic competition of isotactic polypropylene phases.

Conclusions:

• The proposed model provides a quantitative framework for understanding cross-nucleation phenomena.
• The cross-nucleation rate is a key parameter governing the process.
• Temperature plays a critical role in the competitive growth of polymorphs, as seen in isotactic polypropylene.