Tailoring Nanospace

Anita J. Hill^1,2

¹CSIRO Manufacturing and Infrastructure Technology, Private Bag 33 S Clayton MDC 3169 VIC AUSTRALIA, ²Monash University School of Chemistry, Clayton, VIC 3800 AUSTRALIA

anita.hill@csiro.au tel:+61 39545-2777 fax: +61 39544-1128

The nanospace between and along polymer chains has dimensions of order 0.1 nm to a few nm. This unoccupied volume has static and dynamic components, both of which are critical to the transport of gas and vapour molecules and ions through the polymer. Alterations of the nanospace by less than 0.1nm can cause two orders of magnitude variation in flux. The addition of inorganic nanoparticles to polymeric matrices has been utilized over the past few years to tailor transport properties. Most interesting in this work are the unexpected results caused by nanodimensionality: in some cases the addition of non-porous inorganic filler decreases flux but in other cases flux increases. Thus, researchers have explored hybrid or nanocomposite structures of inorganic domains within an organic matrix to produce barrier polymers (low flux) and membrane polymers (high flux). The solid state ionics community has also used incorporation of nanometer-sized domains of an inorganic phase within an organic matrix to improve ionic conductivity of polymer electrolytes. The inability to model and predict these outcomes using current rules of mixing is indicative of the significant effect of the nanoparticle on the packing of nearby polymer chains. This alteration in packing and nanospace can be measured by positron annihilation lifetime spectroscopy (PALS). PALS has been used to study the ortho-Positronium (oPs) accessible nanospace in nanocomposite membrane and barrier polymers as well as nanocomposite polymer electrolytes. The oPs annihilation characteristics are used to measure the effect of nanoparticles on the nanospace through which the ions and molecules move.

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