文档介绍：第六章 疏水材料--超疏水
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1 Wettability
Young’s equation:
cosθ=(γSV –γSL)/ γLV
Hydrophobic: θ›90 ° ;
Hydrophilic
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2、 The theoretics of Supperrepellent material
Wettability
Cassie model
Wenzel model
Young’s equation
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For smooth, flat, uniform solid surface, the relationship between contact angle and surface energy can be described by Yong’s equation (Thomas Young, 1805 ) :
cosθ=(γSV –γSL)/ γLV
Interfacial tension: γSV 、 γSL 、 γLV
Yong’s equation
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Hydrophobic surface
The surface free energy of materials is related to the species and the concentration of the functional surface groups
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Functional surface
Hydrophilic groups:
—OH、—CHO、
—COOH、—NH2
Hydrophobic groups：
—CnH2n+1、
—CH=CH2、
—C6H5、—X、—NO2
—CF3
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Fluorinated polymer
CH2 (36 dyn cm-1) > CH3 (30 dyncm-1) > CF2 (23 dyn cm-1) > CF3 (15 dyn cm-1)
The reason of choosing fluorosilicone
Low surface energy and high surface-active of CF3 group
Improves the adhesion and compatibility
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self-assembly
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For smooth, flat, uniform solid surface, the highest contact angle is only 119º。
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Real solid surface with concave-convex structure
Wenzel model
Cassie model
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Cosθ*=
=r COS θ
Wenzel model：
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Cosθ*=
=r COS θ
Providing θ =110º，if r>， θ* will be larger than 150º
Wenzel model
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Cassie model
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Cosθ’= fcosθ+(1-f)cos180°
= fcosθ+f-1
Area fraction f=Σa/Σ(a+b)
let’s assume that θ =110º，if f is less than , θ’ will be larger than 150º.
Cassie model
Providing CA between liqiud and air is 180°
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PAN Nano fiber material
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Self-cleaning effect
Dirt
LOGO
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Roughening a hydrophobic material
Fabrication
3、The fabricatio