An AFM, XPS and wettability study of the surface heterogeneity of PS/PMMA-r-PMAA demixed thin films.
A series of homopolymer/random copolymer blends was used to produce heterogeneous surfaces by demixing in thin films. The chosen homopolymer is polystyrene (PS) and the random copolymer is poly(methyl methacrylate)-r-poly(methacrylic acid) (PMMA-r-PMAA), whose acidic functions could be used as reactive sites in view of further surface functionalization. The proportion of each polymer at the interface was deduced from X-ray photoelectron spectroscopy (XPS) data using, on the one hand, the O/C ratio, and on the other hand, decomposition of the carbon peak of the blends in two components corresponding to the carbon peaks of PS and PMMA-r-PMAA. Combining the information from XPS with atomic force microscopy (AFM) images, water contact angle measurements and PS selective dissolution, it appears that the surfaces obtained from blends with a high PS content (90/10 to 70/30) display pits with a bottom made of PMMA-r-PMAA, randomly distributed in a PS matrix. On the other hand, the surfaces obtained from blends with a low PS content (30/70 to 10/90) display randomly distributed PS islands surrounded by a PMMA-r-PMAA matrix. The characteristics of the heterogeneous films are thought to be governed by the higher affinity of PMMA-r-PMAA for the solvent (dioxane), which leads to the elevation of the PS phase compared to the PMMA-r-PMAA phase, and to surface enrichment in PMMA-r-PMAA.
Zuyderhoff
Emilienne M
EM
Unité de chimie des interfaces, Université catholique de Louvain, Croix du Sud 2/18, 1348 Louvain-la-Neuve, Belgium.
Dekeyser
Caroline M
CM
Rouxhet
Paul G
PG
Dupont-Gillain
Christine C
CC
D018625:Microscopy, Atomic Force; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D013053:Spectrophotometry; D013499:Surface Properties; D014867:Water / Q000737:chemistry*; D014965:X-Rays
D011137:Polystyrenes; D014867:Water; D019904:Polymethyl Methacrylate