Low Surface Energy PU Film With Small Contact Angle Hysteresis Dou Qizheng

Introductionlotus-effect Beautiful lotus flowers Water droplets Self-cleaning Bar = 20  m Surface roughness Barthlott, et al. Planta 1997, 202, 1

Hydrophobic surface with low surface energy water contact angle,  > 90° Self-Cleaning Properties  : contact angle on a rough surface  0 : contact angle on a projected ‘smooth’ surface Surface roughness enhances the hydrophobicity of hydrophobic surfaces Proper surface roughness (Lotus-alike structure) Wenzel eq. Cassie-Baxter eq. Low roll-off angles small contact angle hysteresis

The force needed for a drop to move over a solid surface (F ): The force needed for a drop to move over a solid surface (F ): F ~  LV (cos  R – cos  A )  LV is the surface tension of the liquid  LV is the surface tension of the liquid Contact angle hysteresis: Contact angle hysteresis:  A –  R or  LV (cos  R – cos  A ) Basic theory

Water contact angle : Advancing: 120º, receding: 60-70º Huge hysteresis: primarily due to the surface reorganization during the contact angle measurements. PDMS Hydrophobic High MW to limit surface reorganization Fluorinated Polyurethane Films LEIS (low-energy ion scattering) First atomic layer, only F and C can be detected

Experimental Preparation of low-surface energy films Preparation of low-surface energy films Polyurethane as polymer matrix Polyurethane as polymer matrix Poly (dimethyl siloxane) (PDMS) will be used as a low-surface energy agent Poly (dimethyl siloxane) (PDMS) will be used as a low-surface energy agent

Polymer Matrix: Solventless Liquid Oligoesters (SLO) and N3600 (cross-linker)

Polyurethane films modified with hydroxyl-terminated PDMS PDMS + SLO + N3600 → PU film of low  Approach 1 Approach 2 PDMS + N3600 → partially PDMS-modified N3600 SLO + N PDMS-N3600 → low  PU (To increase the miscibility between PDMS and other components)

Bi-functional PDMS (2) (1) EFKA 3299 HO-(EO)n-OCH 2 CH 2 CH 2 -(Si(Me) 2 O)x-CH 2 CH 2 CH 2 O-(EO)n-OH n ca. 10 x ca. 20 EO = ethylene oxide, PO = propylene oxide HO-CH 2 CH 2 -OCH 2 CH 2 -(Si(Me) 2 O) n -CH 2 CH 2 O-CH 2 CH 2 -OH n=69

Mono-hydroxyl terminated PDMS (480355): n= 63 Mono-functional PDMS

Water CA and hysteresis of PU film containing EFKA 3299 and cured at room temperature by approach 1 PU film with bi-functional EFKA3299 Surface wettability

PU film with bi-functional Surface wettability PU film containing by approach 1

PU film with bi-functional Surface wettability PU film containing by approach 1

PU film containing by approach 2 PU film with mono-functional Surface wettability

PU film containing by approach 2 PU film with mono-functional Surface wettability

Surface chemical composition PU film with bi-functional PU film containing and cured at 80 o C

Surface chemical composition PU film with mono-functional The chemical composition (Si%) of the PU films which were modified by different amount of and cured under different temperature.

Surface chemical composition PU film with mono-functional The chemical composition (N%) of the PU films which were modified by different amount of and cured under different temperature.

Surface chemical composition PU film with mono-functional The chemical composition (N% and Si%) in different depth of the PU films which were modified by0.07%wt (PDMS) 63 -OH and cured under 40 o C and 120 o C

Surface chemical composition Compare the PU film with and The chemical composition (N% and Si%) in different depth of the PU films which were modified by0.07%wt (PDMS) 63 -OH or 0.08%wt (PDMS) 69 -(OH) 2 and cured under 80 o C

PU film containing EFKA 3299 PU film containing PU film containing Model

1. Increase the roughness of the surface by adding some nano-particles into the film as a additive to get a super- hydrophobic surface. 1. Increase the roughness of the surface by adding some nano-particles into the film as a additive to get a super- hydrophobic surface. Future plans

2. Application of PDMS-modified PU films as anti-fouling coatings. 2. Application of PDMS-modified PU films as anti-fouling coatings. Future plans Coatings containing toxic materials Coatings containing toxic materials Non-toxic Systems Non-toxic Systems Fouling-release coatings based on silicones Fouling-release coatings based on silicones Perform well initially Perform well initially Soft, poor durability, short use life Soft, poor durability, short use life

Acknowledgement Dr. W. Ming Dr. W. Ming Prof. Wang Prof. Wang Prof. Lemstra Prof. Lemstra Dr. Karssenberg Dr. Karssenberg EPG/SMG/SKT group members EPG/SMG/SKT group members DPI DPI