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The Shull Group |
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57. "Interfacial Activity of Gradient Copolymers" Shull, K.R., Macromolecules,
35, 8631 (2002).
Abstract: Numerical self consistent field (SCF) theory is
used to study the equilibrium segregation of A/B gradient copolymers to the
interface between immiscible A and B homopolymers. A generalized SCF theory
is developed that allows arbitrary composition gradients to be investigated.
The focus of this paper is on symmetric copolymers consisting of equal amounts
of A and B repeat units, with a linear or hyperbolic tangent composition gradient.
A gradient parameter, l, is introduced that describes
the length of the composition gradient relative to the length of the entire
copolymer molecule. Critical values of the copolymer chemical potential corresponding
to the formation of copolymer micelles, or to a vanishing interfacial free energy
between A and B homopolymer phases, decrease with l,
and are about 1.6kBT lower for l = 1 than for l
= 0. The width of the concentration profile of A or B repeat units within a
lamellar copolymer phase, or across an emulsified interface, increases with
l, and is equal to about twice the copolymer radius
of gyration for l = 1.