Topography and Surface Composition of Thin Films of Blends of Polystyrene with Brominated Polystyrenes: Effects of Varying the Degree of Bromination and Annealing

A series of thin films of blends of poly(styrene- d 8 ) and poly(styrene- co - p -bromo x -styrene), where 1 ≥ x ≥ 0, cast on to silicon wafers are examined by atomic force microscopy, X-ray photoelectron spectroscopy, and static secondary ion mass spectrometry. Films deposited on wafers stripped of the native oxide are smooth. The poly(styrene- d 8 ) component segregates to the polymer−air interface, and the extent of segregation increases with the degree of bromination. An inverse linear correlation is obtained between the extent of segregation and the polymer compatibility, the latter measured by the interfacial width of bilayer films. For films deposited on wafers retaining the oxide, topographical features are observed with dimensions depending on the blend composition and degree of bromination of the polymer. The bromopolymer forms islands that are raised. The most pronounced topography is found with blends containing the fully brominated styrene. Reducing the degree of bromination increases the polymer compatibility thereby suppressing the formation of topographical features. Changes in topography and surface composition are observed when the films are annealed, leading to dewetting of the substrate.