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

Abstract

The ever-growing catalog of monomers being incorporated into block polymers affords exceptional control over phase behavior and nanoscale structure. The segregation strength, , is the fundamental link between the molecular-level detail and the thermodynamics. However, predicting phase behavior mandates at least one experimental measurement of for each pair of blocks. This typically requires access to the disordered state. We describe a method for estimating from small-angle X-ray scattering measurements of the interfacial width between lamellar microdomains, , in the microphase-separated melt. The segregation strength is determined by comparing to self-consistent field theory calculations of the intrinsic interfacial width, , as a function of the mean-field . The method is validated using a series of independent experimental measurements of and , measured via the order-disorder transition temperature, . The average absolute relative difference between calculated from and the value calculated from is a modest 11%. Corrections for nonplanarity of the interfaces are investigated but do not improve the agreement between the experiments and theory. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.