Preparation of good mechanical property polystyrene nanotubes with array structure in anodic aluminum oxide template usi
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Xilin She and Zhifeng Fu College of Materials Science and Engineering, Beijing University of Chemical Technology, Beijing 100029, China
Jianjiang Li College of Chemical Engineering, Qingdao University, Qingdao 266071, China (Received 26 May 2004; accepted 4 August 2004)
The stable mechanical property polystyrene (PS) nanotubes with array structure were first prepared by filtrating a solution or melt of normal molecular weight PS (Mn ≈ 180,000) into anodic aluminum oxide (AAO) template with only 200-nm pores. The results of transmission electron microscopy and scanning electron microscopy illuminated that PS tubules were successfully obtained and the wall thickness of PS tubules prepared by the 2.5 wt%, 5.0 wt%, and 10.0 wt% PS solution were respectively 50 nm, 70 nm, and 80 nm. The structure of polymer nanotubes depends strongly on the concentration of PS solution. It was found that the wall of the nanotubes derived from melt is thicker than that of the nanotubes from solution. When the polymer solution wets AAO template, a thin polymer film will be formed on the inner porous wall. The thin film/AAO composite membrane acts as a “second-order” template and is soaked repeatedly. So PS solution wets the template and forms nanotubes according to the multi-time wetting mechanism.
I. INTRODUCTION
In recent years, the polymer nanotube, a new branch of nanotubes, has attracted considerable attention because of its outstanding functions and special applications.1,2 Until now, various polymer nanotubes have been prepared in many different ways.3–6 The template method, a simple and very effective method, is best known. Anodic aluminum oxide is usually looked upon as one of the most useful templates because it has homogeneous pores and can be removed easily. Thus, it was usually applied for preparing polymer nanotubes.7–12 As to the reported research on preparing polymer nanotubes by the template method, most of them were derived from conjugated conducting polymers such as polypyrrole,13 polyaniline,14,15 and polythiophene16 by chemical synthesis. However, a few nonconducting polymer nanotubes have been prepared by the physical technique. To our disappointment, this technique requires a
DOI: 10.1557/JMR.2004.0427 3324
J. Mater. Res., Vol. 19, No. 11, Nov 2004
large pore anodic aluminum oxide (AAO) (not less than 400 nm) and a low molecular weight polymer.2,17,18 The commercial AAO membranes usually possess less than 300-nm pores. And the process of enlarging their pores is very difficult and uncontrollable. Especially, the reported nonconducting polymer nanotubes do not possess good mechanical properties because they derived from the Mn ≈ 71,000 poly(vinylidene difluoride) (PVDF),17 the Mn ≈ 85,000 polystyrene (PS),2 and the Mw ≈ 5000 PS.18 Therefore, these disadvantages will limit further research work and wide applications of polymer nanotubes. Herein, we report the successful preparation of good mechanical property PS nanotubes with normal molecular weight PS (Mn ≈ 180,000) in a commercial AAO template (only 200-nm p
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