Nonetheless, these findings were generally in agreement with the DOSY NMR results. Below 24 mM a constant viscosity with a slope of 1.7 was observed for (Z)-II. Above 24 mM, the slope increased to 4.0, indicating oligomerization. In comparison to DOSY NMR data, which indicated a small increase in size, the viscosities measured for II suggest a more significant increase in molecular weight in both concentration regimes. A possible explanation for this is due to the folded shape of (Z)-II. Viscosity, depends also on solvation and shape for instance single stranded DNA has lower intrinsic viscosity than double stranded DNA, however at low ionic strength this trend can be reversed. We thus interpret the data to indicate (Z)-II forms a self-assembled foldamer with shorter more compact and rigid structure. Given diffusion coefficient is correlated with the hydrodynamic radius of a spherical molecule, differences in shape between oligomers of (Z)-and (E)-II are unlikely to be accounted for. This relationship, defined by the Stokes-Einstein equation, may offer a reasonable explanation for the discrepancy between the DOSY and viscosity data. The viscosities for (E)-II increased more steadily with concentration with a slope of 2.6, indicative of concentration dependent polymerization across the concentration gradient; an inflection point for the critical concentration (~24 mM) denoting transition from the cyclic to oligomeric regime in the double logarithmic plot can be perceived (Fig. ). In prior studies, a shorter ditopic synthon bearing UPy units linked via a tetrafluoroazobenzene photoswitch was reported to form cyclic dimers in the Z form which oligomerize with a critical concentration of ~45 mM whereas the E form assembled oligomers according to an isodesmic relationship. In contrast, richer behaviour is observed here; taken together, the DOSY and viscosity data indicate (E)-II appears to prefer self-assembled dimers in the low concentration regime and oligomerizes at higher concentration with a critical concentration of ~24 mM, whilst (Z)-II adopts an intramolecular hydrogen-bonded monomeric configuration at low concentration and oligomerizes at higher concentration with a critical concentration of ~ 24 mM to produces a different self-assembled structure to (E)-II.