Diblock Copolymer Thin Films On Substrates Modified by Random Copolymer Brushes

The self assembly of diblock copolymer thin films into lamellar and cylindrical structures has been proposed as a method of creating small patterns in polymer thin films for electronic materials applications.  A key obstacle, however, is inducing the structures to align perpendicularly, rather than parallel, to the substrate.  To achieve this goal, a “neutral” substrate may be created using a random copolymer brush composed of the species present in the diblock copolymer.  We use self consistent field theory to study the system of diblock copolymer films on random copolymer brushes. Our study focuses on the “neutral window” and examines its dependencies on grafting density, relative chain length between the free and grafted polymers, and blockiness of the random copolymer chains.