Authors: K.W. Lem, J.R. Haw, D.S. Lee, C. Brumlik, S. Sund, S. Curran, P. Smith, S. Brauer, D. Schmidt
Affilation: Konkuk University, Korea
Pages: 889 - 892
Keywords: polymer, nanostructure, composite, crystalline domains, barrier, films, thermal, mechanical, properties, amorphous, semicrystalline
The growth in investment on the effect of size in nanoscience and nanotechnology has been astounding. Among the $12.4B spent in 2006 worldwide Nanotechnology research funding (Lux Research, 2007), at least 50%, that is >$6B, was spent on the effect of size on the development of nanomaterials and devices. The focus of nanoscience is to understand this effect of size and its influence on the properties of material; whereas nanotechnology focuses on exploitation of the size effects to create structures, devices and systems with novel properties and functions. At the nanoscale, materials have different properties as a function of the size compared with the same materials at a larger size. The size range of most interest is typically from 100nm down to approximately 0.2 nm, because in this size range properties of the materials become tunable. Three primary reasons for this tunable behavior are: • Increases in relative surface area • Increases in the % of atoms or molecules on the surface • The dominance of quantum effects. The increase in surface area per unit mass and the % of atom on the surface result in a corresponding increase in chemical reactivity. Thus, some nanomaterials become useful as catalysts to improve the efficiency of fuel cells and batteries, or in “soft” nanotechnology for cosmetics and pharmaceuticals. In addition, as the size of matter is reduced to <100 nm, quantum effects begin to play a role that significantly changes a material’s optical, magnetic, electrical, thermal and mechanical properties. The effect of size on other properties such as surface tension or ‘stickiness’ and thermal transition temperatures are important, because these characteristics directly affect physical and chemical properties. Based on the data reported in the literature to date (Qi, 2009; Henderson et,al, 2004; Briggs et al., 2002), we have demonstrated that the Hall-Petch equation is useful to correlate the some of the observed effect of “effective” nanosize, i.e. thickness, on thermal mechanical properties of amorphous and semicrystalline polymeric films. Several viscoelastic models have been used to determine the role molecular dynamics at the surface interface on thermal mechanical behavior. The polymers examined including polystyrene, polymethyl methacrylate, and MetafuseTM plastics from DuPont.
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