Pathway-Dependent Grain Coarsening of Block Copolymer Patterns under Controlled Solvent Evaporation

Area of Science:

• Materials Science
• Polymer Science
• Chemical Engineering

Background:

• Solvent evaporation annealing (SEA) is an efficient single-step method for processing block copolymers (BCP).
• SEA yields large-grained BCP morphologies rapidly, making it attractive for various applications.
• Understanding the kinetics of BCP grain coarsening is crucial for optimizing SEA.

Purpose of the Study:

• To quantitatively analyze the influence of time and BCP concentration on grain coarsening kinetics in thin films during SEA.
• To develop a mathematical model for BCP ordering under non-stationary conditions.
• To create a predictive tool for engineering BCP processing pathways.

Main Methods:

• Systematic investigation of BCP grain coarsening kinetics at various polymer concentrations.
• Controlled evaporation of solvent to induce annealing.
• Quantitative analysis of lateral grain growth rates.

Main Results:

• Observed a steeply decreasing exponential dependence of the kinetics power-law time exponent on polymer concentration.
• Formulated a mathematical model describing BCP ordering under non-stationary conditions.
• Developed a 2D, time- and concentration-dependent coarsening rate diagram.

Conclusions:

• The study provides a quantitative understanding of BCP grain coarsening during SEA.
• The developed model and diagram can aid in optimizing SEA and other solvent-based directed self-assembly methods.
• Insights gained are applicable to engineering BCP processing for desired morphologies.