The physicochemical characterisation of SSA systems requires the use of multiple complimentary techniques. The self-associative properties of the SSAs, alongside their tert-butyl protected precursors (Figure ) were first explored in the solid state, using single crystal X-ray diffraction techniques. Here, structures obtained from the slow evaporation of solutions containing SSA precursors 2, 4, 6 and 8 demonstrate intermolecular hydrogen bond formation between the urea NH hydrogen bond donor groups to either the urea or ester C=O functionality, as shown in Figure . However, although homogeneous single crystals of 3, 5, 7 and 9 were not obtained, a single crystal of 3 and 5, supplied as a 1:1 enantiomeric mixture was generated. The structure elucidated (Figure ) shows the alternate incorporation of the SSA anion enantiomers into a urea-anion hydrogen bonded tape. Moving into solution, the self-associative properties of this sub-class of amino acid appended SSAs were first explored in DMSO-d6 (Table ), as within this polar organic solvent, SSAs have been shown to produce hydrogen bonded anionic dimers. This enables the quantification of parameters such as SSA anion dimerization constant to be established, which we have shown to correlate with critical aggregation concentration (CAC) values obtained from aqueous solutions of that same SSA. Here, an increase in SSA anionic dimerization constant was shown to correlate with a decreasing CAC, when weighted by a calculated LogP value, obtained for the SSA anion hydrophilic moiety.