Morphology and hydrophobicity of a polyurethane film molded on a porous anodic alumina template

doi:10.1016/j.surfcoat.2004.10.138

Surface and Coatings Technology

Volume 200, Issue 11, 15 March 2006, Pages 3492-3495

https://doi.org/10.1016/j.surfcoat.2004.10.138 Get rights and content

Abstract

Surface characteristics are so paramount that they invariably require surface modification to improve biocompatibility as biomaterials. We describe a method for modulating the morphology and corresponding hydrophobicity of a polyurethane (PU) using PU solution and a suitable porous anodic alumina (PAA) template. The film is characterized by optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and water contact angle measurements. The water contact angle on a molded PU film surface is approximately 152°, much bigger than that of 85° on a free surface formed in air. Super-hydrophobicity is due to the enhanced roughness, which is modulated by a well-designed PAA template surface morphology.

Introduction

Polyurethanes (PU) are widely used as biomaterials due to their good mechanical properties. However, surface-induced thrombosis is one of the major drawbacks that depress their successful applications in blood-contacting artificial medical devices [1]. Thrombosis formation process is always initiated by protein adsorption on PU surfaces, so various methods to prevent thrombosis formation on PU surface have been developed to control protein adsorption by surface modification. These surface modifications may be categorized as chemical or biological surface modifications (surface chemical composition is changed) and physical modifications (surface chemical composition is not changed). The former surface modification generally relates to forming a foreign layer by a grafting, immobilizing, or coating process [2], [3], [4], [5], [6], [7]. The latter surface modification relates to nothing more than controlling morphology formation to change roughness. A rough surface is effective to improving blood compatibility through two ways: one is promoting the neointima propagation on the surface [8], [9], [10], [11], and the other is modulating the surface wettability, enhancing hydrophobicity or enhancing hydrophobicity, which prevents protein adsorption on the surface [12]. Super-hydrophobic surfaces have been obtained by selecting suitable solvents and controlling film-forming temperature [13]. In the present paper, we have prepared a super-hydrophobic a PU film through molding PU coating solution on a porous anodic alumina (PAA) template at room temperature.

Section snippets

Experiments

An aluminum sheet (99.999% purity, 15 mm×60 mm×0.5 mm) was annealed at 773 K for 5 h. Then, it was degreased in alkaline solution followed by electro-polishing under constant voltage 8 V at 288 K for 2 min in a mixed solution of perchloric acid (72%)/ethanol with 1:4 (v/v). Anodizing of aluminum specimens was conducted in H₃PO₄ solution under a constant voltage. Alternative anodizing conditions were used in order to obtain a series of PAA templates with different pore structures.

The PAA

Results and discussions

PU film is colorless and transparent when it is formed on a smooth solid such as flat glass. But it will get opalescent when molded on a rough solid, such as ground glass or PAA template. The two side surfaces of such a molded PU film can be distinguished obviously: one is smooth and bright, and the other is rough and becomes matte. The former surface is the one contacting the air, and the latter one is that contacting the PAA template during PU film formation. The apparent water contact angles

Conclusions

A super-hydrophobic PU film was obtained through molding PU solution on a PAA template. The water contact angle on a molded PU film surface is approximately 152°, much bigger than that of 85° on a free surface formed in air. Super-hydrophobicity is a result of the enhanced roughness, which is modulated by a well-designed PAA template surface morphology.

Acknowledgements

It is a pleasure to thank Zhang Yi, Wang Ying, Wang Sen, and He Suixi for collaborations and valuable discussions.

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Morphology and hydrophobicity of a polyurethane film molded on a porous anodic alumina template

Abstract

Introduction

Section snippets

Experiments

Results and discussions

Conclusions

Acknowledgements

Biomaterials

Biomaterials

Polym. Degrad. Stab.

Biomaterials

Biomaterials

Biomaterials

Biomaterials