Eur. Phys. J. B 4, 325-332 (1998)
https://doi.org/10.1007/s100510050387

Phase behavior of binary blends of symmetric polystyrene-polybutadiene diblock copolymers studied using SANS

¹ Condensed Matter Physics and Chemistry Department, Risø National Laboratory, P.O. Box 49, 4000 Roskilde, Denmark
² IMFUFA (Department of Mathematics and Physics), Roskilde University, P.O. Box 260, 4000 Roskilde, Denmark

Corresponding author: ^a Christine.Papadakis@risoe.dk

Received: 9 February 1998
Revised: 20 April 1998
Accepted: 24 April 1998
Published online: 15 August 1998

Abstract

Binary blends of compositionally symmetric diblock copolymers are investigated using small-angle neutron scattering. The study focuses on the miscibility of blends of polystyrene-polybutadiene diblock copolymers as a function of chain length ratio and blend composition, and the results are related to the theoretical phase diagram put forward by M.W. Matsen (J. Chem. Phys. 103, 3268 (1995)). Three different low molar mass copolymers were blended with a high molar mass copolymer. We find very good coincidence with the theoretical phase diagram obtained. Only for blends having a chain length ratio of 0.06, theory predicts that a larger amount of short copolymers can be dissolved in the matrix of long copolymers, and vice versa. With the latter blends and volume fractions of short chains between 0.11 and 0.70, the second-order Bragg-peaks do not vanish, which indicates that the lamellae are asymmetric.