Hyaluronic acid and polyalkylene glycol (PAG) based materials have been found to exhibit a synergistic interaction, in which the viscosity of the mixture is more than twice as high as the viscosity expected from the viscosity of the individual components. The mixture otherwise has similar properties...http://www.google.com.au/patents/US7074424?utm_source=gb-gplus-sharePatent US7074424 - Polyalkylene glycol viscosity-enhancing polymeric formulations