Eur. Phys. J. E (2016) 39: 43
https://doi.org/10.1140/epje/i2016-16043-4

Regular Article

Confinement effects on the miscibility of block copolymer blends

Department of Chemical Engineering, Department of Physics & Astronomy, and the Waterloo Institute for Nanotechnology, University of Waterloo, Waterloo, Ontario, Canada

^* e-mail: r6spence@uwaterloo.ca
^** e-mail: mwmatsen@uwaterloo.ca

Received: 21 February 2016
Revised: 26 March 2016
Accepted: 30 March 2016
Published online: 22 April 2016

Abstract

Thin films of long and short symmetric AB diblock copolymers are examined using self-consistent field theory (SCFT). We focus on hard confining walls with a preference for the A component, such that the lamellar domains orient parallel to the film with an even number of monolayers. For neat melts, confinement causes the lamellar period, D , to deviate from its bulk value, D_b, in order to be commensurate with the film thickness, i.e., . For blends, however, the melt also has the option of macrophase separating into large and small monolayers so as to provide a better fit, where . In addition to performing full SCFT calculations of the entire film, we develop a semi-analytical calculation for the coexistence of thick and thin monolayers that helps explain the complicated interplay between miscibility and commensurability.