ABSTRACT: Two new block copolymers containing dimethylsiloxane and semifluorinated styrene blocks (BSF6 and BSF8) were prepared using a polysiloxane azo-macroinitiator and corresponding semifluorinated styrene monomers StyF6 and StyF8. The thermal properties of the block copolymers were investigated by DSC, which showed the formation of a thermotropic mesophase in BSF8. This was attributed to the self-assembly of the semifluorinated side groups in microphase separated domains of the incompatible polymer blocks. Coatings with 300 nm thicknesses had a root mean square roughness of 10 nm by atomic force microscopy. Using water and alcohols, wetting behavior was studied along with a model polydimethysiloxane (PDMS) network. High advancing (θadv = 122°) and receding (θrec = 82°) water contact angles were observed for BSF8. Using 2-propanol, BSF8 displayed oleophobicity (θadv = 64° and θrec = 45°) while a reference PDMS coating was completely wetted (θadv = θrec = 0°). Utilizing θadv for a series of alcohols, a fit to a modified equation of state gave a low value for BSF8 surface tension (γSV = 10.5 mN/m). Both the wetting behavior of BSF8 and surface dynamics associated with wetting are consistent with the presence of a well-ordered, liquid crystalline fluorocarbon surface domain. In contrast, BSF6 surfaces are swollen by alcohols and display a cycle-dependent wetting behavior in water. BSF6 surfaces are thus labile to surface reorganization and/or solvent adsorption.
Wetting Behavior of Films of New Fluorinated Styrene-Siloxane Block Copolymers
GALLI, GIANCARLO;CHIELLINI, EMO;
2004-01-01
Abstract
ABSTRACT: Two new block copolymers containing dimethylsiloxane and semifluorinated styrene blocks (BSF6 and BSF8) were prepared using a polysiloxane azo-macroinitiator and corresponding semifluorinated styrene monomers StyF6 and StyF8. The thermal properties of the block copolymers were investigated by DSC, which showed the formation of a thermotropic mesophase in BSF8. This was attributed to the self-assembly of the semifluorinated side groups in microphase separated domains of the incompatible polymer blocks. Coatings with 300 nm thicknesses had a root mean square roughness of 10 nm by atomic force microscopy. Using water and alcohols, wetting behavior was studied along with a model polydimethysiloxane (PDMS) network. High advancing (θadv = 122°) and receding (θrec = 82°) water contact angles were observed for BSF8. Using 2-propanol, BSF8 displayed oleophobicity (θadv = 64° and θrec = 45°) while a reference PDMS coating was completely wetted (θadv = θrec = 0°). Utilizing θadv for a series of alcohols, a fit to a modified equation of state gave a low value for BSF8 surface tension (γSV = 10.5 mN/m). Both the wetting behavior of BSF8 and surface dynamics associated with wetting are consistent with the presence of a well-ordered, liquid crystalline fluorocarbon surface domain. In contrast, BSF6 surfaces are swollen by alcohols and display a cycle-dependent wetting behavior in water. BSF6 surfaces are thus labile to surface reorganization and/or solvent adsorption.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
