Nearly 40% new drugs are poorly water-soluble.To achieve good oral absorption of these compounds, solubilisation in the gut fluid is extremely important.Water-soluble polymers can improve the absorption of these drugs.To date there is no insight into the effect of gut bile salts on the in vivo behaviour of water-soluble polymer based oral delivery systems for poorly soluble drugs.The aim of this project is to understand the effects of the polymer-bile salts interactions on the solubilisation process of poorly water-soluble compounds using SESANS. A better understanding of the polymer-bile salt interaction through a structural characterisation of the polymer-surfactant assemblies (100-300nm) by SESANS can provide useful guidance on polymer selection,rationalising formulation development and lead to the generation of new bio-polymers designed for the effective drug delivery.