Incorporation of silver nanoparticles coated with mercaptosuccinic acid/ poly(ethylene glycol) copolymer into epoxy for enhancement of dielectric properties Hua Ren, Shaochun Tang, Junaid Ali Syed, Xiangkang Meng * Institute of Materials Engineering, National Laboratory of Solid State Microstructures and College of Engineering and Applied Science, Nanjing University, Jiangsu, PR China highlights < Novel route to the synthesis of MSA/PEG copolymer-coated silver nanoparticles developed. < The size of silver nanoparticles is successfully controlled use different copolymer. < Developed silvereepoxy nanocomposites exhibit huge increase in dielectric constant. article info Article history: Received 30 March 2012 Received in revised form 12 September 2012 Accepted 7 October 2012 Keywords: Silver nanoparticles Epoxy resin Nanocomposites Electronic characterisation abstract A novel route to the synthesis of polymer-coated silver nanoparticles (NPs) was developed on the basis of the reduction of Tollens’ reagent using mercaptosuccinic acid/poly(ethylene glycol) (MSA/PEG) copol- ymer as reducing agent and stabilizer simultaneously. The average size of the polymer-coated silver NPs could be controlled in a wide range from 10 to 120 nm by changing the MSA/PEG molar ratio. These surface-coated silver NPs can be uniformly dispersed in polar solvent and a homogeneous silver NPs/ acetone dispersion has been prepared. Silvereepoxy nanocomposites have been developed by incor- porating these silver NPs into epoxy. The nanocomposites with silver volume content of 25% showed a more than 3000% increase in dielectric constant as compared to neat matrix and a relatively low dielectric loss below 0.05, which meets the main requirement for embedded decoupling capacitors. Moreover, thermal properties of the silvereepoxy nanocomposites were also characterized by ther- mogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The initial decompo- sition temperature and glass transition temperature were elevated with the increase of silver content, which exhibit great thermal stability and facilitate electrical applications requiring higher heat- resistance. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Incorporation of inorganic nanoparticles (NPs) into polymer matrix offers enormous possibilities for the design of functional materials with significant technological applications. Metal- polymer nanocomposites can be applied for the development of embedded-capacitor technology [1], surface enhanced Raman spectroscopy substrates [2], antibacterial materials [3], sensors [4], etc. Physical properties of these nanocomposites mainly depend on the distribution status of metallic NPs in polymer matrix and the structural compatibility of NPs toward polymeric molecules. Therefore, the key to obtain metal-polymer nanocomposites with optimized-performance is controlling the geometric size and spatial dispersion of the NPs, avoiding unexpected aggregation or agglomeration. General methods for preparation of metal particles (e.g., silver, gold, platinum, etc.) are based on the reduction of precursor ions, using various reducing agents including sodium borohydride [5], hydrazine hydrate [6], etc. Typical approaches used to minimize aggregation include proper functionalization of the NPs to make them compatible with polymeric host and selection of an adequate process, such as rapid precipitation or ultrasonication, to diminish the probability of clustering [7]. However, reaction rates are rela- tively high by using these strong reducing agents, which makes the size monodispersity and aggregation hard to be controlled by reaction conditions. Slow down the reaction rate and bring * Corresponding author. Tel.: þ86 25 83685585; fax: þ86 25 83595535. E-mail address: mengxk@nju.edu.cn (X. Meng). Contents lists available at SciVerse ScienceDirect Materials Chemistry and Physics journal homepage: www.elsevier.com/locate/matchemphys 0254-0584/$ e see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.matchemphys.2012.10.024 Materials Chemistry and Physics 137 (2012) 673e680