After characterizing their photoswitching capabilities, the propensity for I-III to form supramolecular polymers was investigated using 1 H DOSY NMR. Initially, samples of I were prepared at 4 mM (deuterochlroform); at this concentration a small difference in diffusion coefficient (D) was observed upon photoswitching (as evidenced from the 1 H NMR). When converted to molecular weight (Mw, vide infra), these D values indicate the size of the E-I and Z-I species is similar and that the respective photostationary states are likely monomeric. In contrast at 4 mM, II exhibited a larger difference in diffusion coefficient (D) between the E and Z form suggesting a significant difference in molecular weight (which we attribute to formation of cyclic dimers vide infra). A similar but less pronounced difference in D was observed for III. Next, DOSY spectra were acquired at a range of concentrations of each supramolecular synthon (4 -56 mM). As concentration increased, there was a decrease in D for all building blocks (Fig. ) indicating an increase in size of the species. For I, at low concentrations (< 24 mM), D decreased slightly for the Z isomer, whilst for the E isomer a similar trend was observed; D values were consistently slightly smaller for the E isomer than those for the Z isomer. Whilst these data imply limited chain elongation at lower concentrations this minor difference might be associated with the proclivity for the Z isomer to favour cyclic oligomers and the E isomer to favour extended oligomers (see later). At higher concentrations of I (> 24 mM) the behaviour differed, with the size of both the E and Z isomers both increasing to a comparable degree. This indicated a switch in the ring-chain equilibria from cyclic species to chain extended oligomers. From these data, it was possible to calculate an approximate molecular weight (Mw) for each isomer at each concentration.