Nanodiamond and onion-like carbon polymer nanocomposites O. Shenderova a , T. Tyler a , G. Cunningham a, ⁎ , M. Ray a , J. Walsh a , M. Casulli a , S. Hens a , G. McGuire a , V. Kuznetsov b , S. Lipa c a International Technology Center, Raleigh, NC 27715, USA b Boreskov Institute of Catalysis, Novosibirsk, Russia c North Carolina State University, Raleigh, NC, 27695, USA Available online 16 January 2007 Abstract The current work demonstrates that nanodiamond (ND) of detonation origin and onion-like carbon (OLC) are valuable additives in multifunctional polymer composites, particularly for polymers used in microelectronic applications. We demonstrate that addition of ND to a polyimide matrix increases the thermal degradation temperature of the composites up to 30 °C and also improves adhesion. The addition of 2 wt.% of ND increases thermal conductivity of PDMS up to 15%. Finally, we also demonstrate that the addition of OLC to polydimethylsiloxane and polyurethane matrices increases the loss tangent of the composites. Published by Elsevier B.V. Keywords: Diamond crystal; Nanoparticles; Nanotechnology 1. Introduction Previous reports demonstrated that nanodiamond (ND) particles synthesized by the detonation of carbon-containing explosives are potential nano-additives for metallic and polymeric matrices [1,2]. Detonation ND, with ∼ 5 nm average primary particle size, is chemically and mechanically stable and can withstand high temperatures during composite processing. Nanodiamond-based nanoelements are readily functionalized, including functionalization which promotes cross-linking with polymer chains during nanocomposite curing [1–3]. The addition of ND to structural polymers results in an increase in mechanical strength, wear-resistance, and heat-aging resistance [1,2]. Highly effective coatings based on the incorporation of ND in fluoroelastomers and polysiloxanes have been developed, and the elastic modulus and strength of rubbers based on poly- isoprene, butadiene–styrene, butadiene–nitrile, as well as natural rubbers, have been considerably improved [1,2]. An increase in cross-linking is one mechanism to explain the increased polymer composite strength resulting from ND addition [2]. In the current paper we explore ND-based polymer composites for several other applications. One of the important areas of application, where novel polymer nanocomposites can provide a breakthrough, is microelectronics, particularly the low-k class of polymers for inter-level dielectrics. As a rule, materials possessing a low dielectric constant (k) also exhibit low thermal conductivity [4]. Heat dissipation is already a concern for many high speed microprocessor chips and will become an issue for other devices as device dimensions continue to shrink [5]. As a result, the thermal properties (temperature of thermal degradation, thermal conductivity) of polymer dielectrics must be addressed. In order to achieve a low dielectric constant for polymer based dielectrics, fluorine is often incorporated into the chemical structure. The addition of fluorine, however, often results in a lower thermal stability [4]. As a result, there is a balance between achieving a low dielectric constant for polymers and maintaining acceptable thermal stability. Additionally, due to the high levels of fluorine content in such polymers, adhesion to adjacent layers is often a problem. Below we demonstrate that the thermal degradation and adhesion properties of low-k dielectrics can be improved by using ND-polymer composites. A process of incorporating ND into a polyimide matrix (k ∼ 3.4) and the properties of such composites are reported. In addition to polyimide, several other polymer matrices, with incorporation of 1–2 wt.% of nanodiamond particles, were Diamond & Related Materials 16 (2007) 1213 – 1217 www.elsevier.com/locate/diamond ⁎ Corresponding author. International Technology Center, 8100 Brownleigh Dr. Suite 120, Raleigh, NC 27617-7300, USA. Tel.: +1 919 881 0250; fax: +1 919 881 0440. E-mail address: gcunningham@itc-inc.org (G. Cunningham). 0925-9635/$ - see front matter. Published by Elsevier B.V. doi:10.1016/j.diamond.2006.11.086