Orienting Ion-Containing Block Copolymers Using AC Electric Field

Abstract

We consider orientation mechanisms for block copolymers in an electric field. Theoretical and experimental studies have shown that nonuniformity of the dielectric constant gives rise to a preferred orientation of the melt with respect to the applied field. We show that the presence of ions, as found in anionically prepared copolymers, may increase the alignment effect markedly. Time-varying (ac) and static (dc) fields are considered within a unified framework. We find that orientation of block copolymers can in principle be achieved without a dielectric contrast if there is a mobility contrast. The presence of ions is especially important at small field frequencies, as is in most experiments. Unlike the no-ions case, it is found that orienting forces depend on the polymer chain lengths. The mobile-ions mechanism suggested here can be used to reduce the magnitude of orienting fields as well as to discriminate between block copolymers of different lengths.

8 pages, 2 figures

References in corpus (2)

• Thin Film Diblock Copolymers in Electric Field: Transition from Perpendicular to Parallel Lamellae
• Structural changes in block copolymers: coupling of electric field and mobile ions

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• Electrostatic Cancellation of Gravity Effects in Liquid Mixtures
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• Motion of a transverse/parallel grain boundary in a block copolymer under oscillatory shear flow