Showing papers by "Kenneth R. Shull published in 1993"

Segment distributions in lamellar diblock copolymers

Abstract: Predictions from a self-consistent-field theory of inhomogeneous polymer systems are compared to results obtained from neutron reflectivity studies fo ordered lamellar diblock copolymers and their blends with homopolymers. Previously measured distributions of chain ends and junction points in neat diblock copolymers, and of homopolymers in diblock copolymer/homopolymer blends, were found to be in quantitative agreement with theory. By extending the theory to more strongly segregated systems, we show that relatively weak centralization of chain ends within the appropriate domain of a lamellar diblock copolymer is expected in all cases

Interfacial phase transitions in block copolymer/homopolymer blends

Abstract: A theoretical treatment of A-B diblock copolymer aggregation in matrices of homopolymer A is developed. These aggregates, termed «bulk» micelles when they form within a homogeneous matrix phase and surfaces micelles when they form at a surface or interface, can be pointlike (spherical), linear (cylindrical), or planar (lamellar). Bulk micelles set the limiting value of the copolymer chemical potential which can be obtained in a given system. Surface micelles will be formed at lower copolymer chemical potentials when the surface has a preferential affinity for the B repeat units which make up the micelle core

Topological coarsening of symmetric diblock copolymer films: Model 2D systems.

Abstract: Films of diblock copolymers with thicknesses less than a lamellar period on a noninteracting surface were found to be model systems for studying the late stages of two dimensional phase separation. It was found under conditions of constant surface coverage that the average particle size , the inverse of the total number of particles N(t) -1 , and the correlation length ξ(t) varied as t a , t 2a , and t a , respectively, where a=0.23±0.03