TY - JOUR

T1 - Wetting description of block copolymer thin films

AU - Milner, Scott T.

AU - Morse, David C.

PY - 1996

Y1 - 1996

N2 - Symmetric diblock copolymers undergo a weakly first-order microphase separation transition to a lamellar phase. In a thin film of thickness d this transition is altered for two reasons: the film geometry imposes commensurability restrictions on the concentration profiles, and the surface field favors one of the two blocks. The latter effect dominates for d>ξ, where ξ is the correlation length near [Formula Presented]. We construct a wetting Hamiltonian, in which the slowly varying amplitude ψ(z) of the composition c(z)=2ψ(z)cos([Formula Presented]z) is the order parameter, and explore the changes in the profile induced by changes in temperature, surface field, and d/ξ. The resulting phase diagram exhibits a line of first-order prewetting transitions ending in a critical point, and a capillary condensation transition to an ordered film. Turning to commensurability effects, we compute the ranges of thickness near half-integer numbers of layers for which the free surface of a copolymer film is unstable to capillary waves, analogous to spinodal decomposition in two dimensions.

AB - Symmetric diblock copolymers undergo a weakly first-order microphase separation transition to a lamellar phase. In a thin film of thickness d this transition is altered for two reasons: the film geometry imposes commensurability restrictions on the concentration profiles, and the surface field favors one of the two blocks. The latter effect dominates for d>ξ, where ξ is the correlation length near [Formula Presented]. We construct a wetting Hamiltonian, in which the slowly varying amplitude ψ(z) of the composition c(z)=2ψ(z)cos([Formula Presented]z) is the order parameter, and explore the changes in the profile induced by changes in temperature, surface field, and d/ξ. The resulting phase diagram exhibits a line of first-order prewetting transitions ending in a critical point, and a capillary condensation transition to an ordered film. Turning to commensurability effects, we compute the ranges of thickness near half-integer numbers of layers for which the free surface of a copolymer film is unstable to capillary waves, analogous to spinodal decomposition in two dimensions.

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U2 - 10.1103/PhysRevE.54.3793

DO - 10.1103/PhysRevE.54.3793

M3 - Article

AN - SCOPUS:0030263570

SN - 1539-3755

VL - 54

SP - 3793

EP - 3810

JO - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

JF - Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

IS - 4

ER -