The overall aim of this project is to reduce uncertainties in aerosol hygroscopic growth through measurement of the largest available library of compounds to refine equilibrium state models. Equilibrium hygroscopicity curves of simple straight chain dicarboxylic acids have been used to parametrise thermodynamic models (UNIFAC, E-AIM and AIOMFAC). Here we present equilibrium hygroscopicity curves of dicarboxylic acid molecules of increasing molecular complexity through the addition of single or multiple methyl, ethyl branching groups. On comparison with thermodynamic model predictions we conclude that UNIFAC parametrisations do not reproduce experimental observations. Further to this we also present data for a wide range of amino acids, sugars and alcohols to allow for key structural comparisons and the relationship between molecular structure and water uptake to be investigated.