1 Polymer nanocomposites with core cross-linked star polymers Steven Spoljaric 1 , Antonietta Genovese 1 , Tor Kit Goh 2 , Greg Qiao 2 , Balaji Rengarajan 1, * and Robert Shanks 1 1 School of Applied Sciences, RMIT University, GPO Box 2476V, Melbourne 3001, Australia 2 School of Chemical and Biomolecular Engineering, University of Melbourne, Australia balaji.rengarajan@rmit.edu.au 1. Introduction Star polymers are of increasing academic interest (Figure 1) and in industry due to their unique properties and greater availability. They are the simplest of hyperbranched polymers consisting of a number of linear branches or ‘arms’ connected to a central core [1]. Within this hyperbranched group, several classes can be used to subcategorise star polymers. Multi- arm star polymers are those where the polyfunctional core focal points determine the number of arms [2]. Another type includes those with a crosslinked ‘hard’ core and ‘soft’ linear arms, known as core-crosslinked star (CCS) polymers. These CCS star polymers are known to exhibit remarkable properties despite their high molecular weight. Figure 1 Annual number of refereed publications in the field of highly branched and hyperbranched molecules [3] The number of arms (functionality or f) and their length primarily influence the properties of star polymers, which include enhanced mechanical, gas barrier and rheological properties [4]. As a result, star polymers have found use in a number of industrial applications, such as polyisoprene stars as viscosity index modifiers in the petroleum industry (marketed as “Shelvis”, by Shell Chemical Co.), acrylic stars used to improve oxygen permeability and mechanical properties in contact lenses and commercial stars used as binders in toners for International Conference on Polymer Blends. Editor: S. Thomas, Mahatma Gandhi University, Kottayam, Kerala, India. 2: P12, 11-14.