Control of surface properties using fluorinated polymer brushes produced by surface-initiated controlled radical polymerization.
Surface-grafted styrene-based homopolymer and diblock copolymer brushes bearing semifluorinated alkyl side groups were synthesized by nitroxide-mediated controlled radical polymerization on planar silicon oxide surfaces. The polymer brushes were characterized by X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and time-dependent water contact angle measurements. Angle-resolved XPS studies and water contact angle measurements showed that, in the case of the diblock copolymer brushes, the second block to be added was always exposed at the polymer-air interface regardless of its surface energy. Values of z*/Rg were estimated based on the radius of gyration, Rg, of the grafted homopolymer or block copolymer chains for the grafted brushes and thickness of the brush, z*. The fact that z*/Rg > 1 suggests that all these brushes are stretched. These results support the idea that after grafting the first block onto the surface the nitroxide-end capped polymer chains were able to polymerize the second block in a "living" fashion and the stretched brush so formed was dense enough that the outermost block in all cases completely covers the surface. NEXAFS analysis showed a relationship between the surface orientation of the fluorinated side chains and brush thickness with thicker brushes having more oriented side chains. Time-dependent water contact angle measurements revealed that the orientation of the side chains of the brush improved the surface stability toward reconstruction upon prolonged exposure to water.
Andruzzi
Luisa
L
Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853, USA.
Hexemer
Alexander
A
Li
Xuefa
X
Ober
Christopher K
CK
Kramer
Edward J
EJ
Galli
Giancarlo
G
Chiellini
Emo
E
Fischer
Daniel A
DA
D000042:Absorption; D005465:Fluorocarbon Polymers / Q000737:chemistry*; D015394:Molecular Structure; D012822:Silicon Dioxide / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission / Q000379:methods; D020058:Styrene / Q000737:chemistry; D013499:Surface Properties; D013997:Time Factors; D014965:X-Rays
D005465:Fluorocarbon Polymers; D020058:Styrene; D012822:Silicon Dioxide