Estimating the Segregation Strength of Microphase-Separated Diblock Copolymers from the Interfacial Width

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Block polymers offer tunable phase behavior and nanoscale structures through monomer selection.
• Segregation strength (χN) is crucial for linking molecular properties to polymer thermodynamics.
• Predicting polymer phase behavior typically requires experimental measurement of χN in the disordered state.

Purpose of the Study:

• To develop and validate a novel method for estimating polymer segregation strength (χN).
• To utilize small-angle X-ray scattering (SAXS) measurements of interfacial width (tx) in the microphase-separated state.
• To provide an alternative to traditional methods requiring access to the disordered polymer state.

Main Methods:

• Estimated χN by comparing experimental interfacial width (tx) with self-consistent field theory (SCFT) calculations of intrinsic interfacial width (ti).
• Validated the method using independent experimental measurements of tx and χN derived from the order-disorder transition temperature (TODT).
• Investigated corrections for interfacial nonplanarity to assess their impact on theoretical agreement.

Main Results:

• Successfully estimated χN from interfacial width measurements (tx).
• Achieved an average absolute relative difference of 11% between χN calculated from tx and χN from TODT.
• Found that corrections for interfacial nonplanarity did not significantly improve agreement between experiment and theory.

Conclusions:

• The developed method provides a reliable alternative for estimating polymer segregation strength (χN) from the microphase-separated state.
• This approach simplifies the prediction of block polymer phase behavior by avoiding the need to access the disordered state.
• The findings contribute to a better understanding of polymer thermodynamics and self-assembly.