Pathway complexity in fibre assembly from liquid crystals to hyper-helical gelmorphs [dataset]

A chiral acyl-semicarbazide gelator 1RR/SS undergoes self-assembly to give three different supramolecular gels of differing fibre morphology (‘gelmorphs’) as well as lyotropic liquid crystalline droplets depending on the assembly pathway. The three gels have either hyperhelical (HH-gel), tape-fibre (TF-gel) or thin fibrils derived from the liquid crystalline phase (LC-gels). The gels exhibit very different rheological properties with elastic modulus, G′, and yield stress decreasing in the order HH > TF > LC and separated by an order of magnitude in each case. The gelator 1RR/SS exists as three slowly interconverting conformers (termed conformers C, B and A) in solution in the ratio 78:21:1, respectively and are self-associated in solution. XRPD data on the freeze dried gels show that all three gels comprise the unsymmetrical, intramolecular hydrogen bonded conformer B which is the least soluble component. In the solid state, however, material comprising conformer B is unstable and slowly converts to crystalline conformer A, an extended linear form which is the minor component in solution. The kinetics of gel fibre assembly have been monitored by circular dichroism spectroscopy which show that formation of the remarkable HH-gels by sonication at 25 oC is cooperative and may well involve association of the growing fibril with major conformer C as a chaperone. In contrast, formation of the TF-gels at 70 oC is isodesmic. This single molecule dynamic conformational library shows how very different materials with different morphology and hence very different materials properties can arise from pathway complexity as a result of emergent interactions during the assembly process.