Materials Science

Stickier with SWNTs

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Science  17 Nov 2006:
Vol. 314, Issue 5802, pp. 1051
DOI: 10.1126/science.314.5802.1051a

Adhesives that bond quickly and firmly to most surfaces on application of only a small amount of pressure are increasingly sought to eliminate the need for chemical activators or crosslinkers. Under tension, such pressure-sensitive adhesives form cavities that expand into fibrils, which in turn extend before detaching from the surface; it is these processes that contribute to the energy of adhesion. Wang et al. explored the adhesive properties of a poly(butyl acrylate) dispersion mixed with single-walled carbon nanotubes (SWNTs) that were functionalized with poly(vinyl alcohol) to confer hydrophilicity. They found that the SWNTs had the somewhat surprising effect of rendering the polymer both stiffer and more dissipative, two characteristics that usually vary in opposing fashion. Improved adhesive properties resulted from SWNT loading as low as 0.05 weight %, with 0.3 weight % proving optimal. During debonding, the SWNTs were found both to reduce the nucleation of cavities and to stabilize the walls between cavities, thus allowing them to absorb more energy before detachment from the substrate as fibrils. The optimized material also exhibited high optical clarity and a 10-order-of-magnitude increase in conductivity. These features bode well for eventual applications of this relatively environmentally benign material in electronics and displays. — MSL

Adv. Mater. 18, 2730 (2006).

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