Interfacial reaction-induced roughening in polymer thin films

Area of Science:

• Polymer Science
• Materials Science
• Chemical Engineering

Background:

• Reactive blending of immiscible polymers is crucial for creating advanced materials with enhanced properties.
• Understanding the interplay between reaction kinetics and morphology evolution is key to controlling blend characteristics.

Purpose of the Study:

• To investigate the reaction dynamics and morphology evolution during reactive blending of immiscible polymers using a phase-field model.
• To explore the influence of various parameters, including interface shapes, layer thicknesses, reaction rates, and polymer interaction strength, on blend formation.

Main Methods:

• Utilized a phase-field model to simulate diffusive transport and reaction in layered films of end-reactive polymers.
• Systematically varied parameters such as Damkohler number (Da_f), Flory-Huggins interaction parameter (χ), and film thickness.
• Investigated the effects of reversible reactions, fraction of reactive end groups, and thermal fluctuations.

Main Results:

• Interfacial roughening and spontaneous emulsion formation were observed, influenced by film thickness, reaction rate, and polymer miscibility.
• Thicker films and higher χ values led to slower reaction and later roughening.
• Increasing Da_f accelerated the reaction and roughening onset.
• A critical concentration of the reaction product (diblock) was necessary for roughening and emulsification.

Conclusions:

• The study elucidates the mechanisms governing morphology evolution in reactive polymer blending.
• Identified key parameters controlling spontaneous emulsification, providing insights for material design.
• Demonstrated the significant role of reaction product concentration and thermal fluctuations in initiating and sustaining emulsification.