Decoupling Substrate Surface Interactions in Block Polymer Thin Film Self-Assembly

Abstract

We report a highly predictive approach to capturing the major substrate–polymer interactions that can dominate nanoscale ordering and orientation in block polymer (BP) thin films. Our approach allows one to create designer BP thin films on modified substrates while minimizing the need for extensive parameter space exploration. Herein, we systematically and quantitatively examined the influence of substrate surface energy components (dispersive and polar interactions) on thin film self-assembly, and our analysis demonstrates that although total surface energy plays a dominant role in substrate wetting, individual contributions from the dispersive and polar components of the surface energy influence the composite through-film behavior. Additionally, long-range forces as described by the Hamaker constant are under-recognized factors in thin film assembly and can alter expected wetting behavior by affecting thermodynamic stability. This more inclusive interpretation of surface energy effects, including the Hamaker constant, on BP thin films was supported by studies of interfacial and through-film behavior as gleaned from temporal island/hole measurements via in situ optical microscopy during thermal annealing. The formalism correctly predicted experimental wetting and hole formation sizes over a wide range of substrate surface energies when employing the appropriate relationships based on decoupled dispersive and polar components. Our results indicate a promising and more universal approach for matching desired BP thin film self-assembly with chemically tailored substrate modifications.