Equilibrium surface composition of diblock copolymers

The surface composition of a series of symmetric diblock copolymers of polystyrene (PS) and polymethylmethacrylate (PMMA) was studied using x-ray photoelectron spectroscopy (XPS). Each copolymer was composed of N segments where N ranged from 270 to 5200. At large N, where the system is highly segreg...

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Bibliographic Details
Published in:The Journal of chemical physics 1990-01, Vol.92 (2), p.1478-1482
Main Authors: GREEN, P. F, CHRISTENSEN, T. M, RUSSELL, T. P, JEROME, R
Format: Article
Language:English
Subjects:
360602 - Other Materials- Structure & Phase Studies
Applied sciences
CHAINS
CHEMICAL COMPOSITION
COPOLYMERS
ELECTRON SPECTROSCOPY
ENERGY
ESTERS
Exact sciences and technology
FREE ENERGY
INTERACTIONS
MATERIALS
MATERIALS SCIENCE
ORGANIC COMPOUNDS
ORGANIC POLYMERS
PETROCHEMICALS
PETROLEUM PRODUCTS
PHOTOELECTRON SPECTROSCOPY
PHYSICAL PROPERTIES
Physicochemistry of polymers
PLASTICS
PMMA
POLYACRYLATES
POLYMERS
POLYOLEFINS
POLYSTYRENE
POLYVINYLS
Properties and characterization
SPECTROSCOPY
SURFACE ENERGY
SURFACE PROPERTIES
SYNTHESIS
SYNTHETIC MATERIALS
THERMODYNAMIC PROPERTIES
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Summary:The surface composition of a series of symmetric diblock copolymers of polystyrene (PS) and polymethylmethacrylate (PMMA) was studied using x-ray photoelectron spectroscopy (XPS). Each copolymer was composed of N segments where N ranged from 270 to 5200. At large N, where the system is highly segregated, the surface is composed only of PS, the lower surface energy component. For smaller N, where the system is in the weak segregation limit, both the PS and PMMA segments coexist at the surface. The surface excess ψ1 of PS in the weak segregation limit is well described by ψ1=α−βN−1/2, in good agreement with mean field predictions. The constants α and β depend on the interactions between the unlike segments on the copolymer chain and on the surface energy differences between the components. We also show that the strength of the segmental interactions in the vicinity of the surface are weaker than from those in the bulk.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.458106