title: A direct comparison of one- and two-component dendritic self-assembled materials: elucidating molecular recognition pathways.
abstract: This paper compares and contrasts, for the first time, one- and two-component gelation systems that are direct structural analogues and draws conclusions about the molecular recognition pathways that underpin fibrillar self-assembly. The new one-component systems comprise l-lysine-based dendritic headgroups covalently connected to an aliphatic diamine spacer chain via an amide bond. One-component gelators with different generations of headgroup (from first to third generation) and different length spacer chains are reported. The self-assembly of these dendrimers in toluene was elucidated using thermal measurements, circular dichroism (CD) and NMR spectroscopies, scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). The observations are compared with previous results for the analogous two-component gelation system in which the dendritic headgroups are bound to the aliphatic spacer chain noncovalently via acid-amine interactions. The one-component system is inherently a more effective gelator, partly as a consequence of the additional covalent amide groups that provide a new hydrogen bonding molecular recognition pathway, whereas the two-component analogue relies solely on intermolecular hydrogen bond interactions between the chiral dendritic headgroups. Furthermore, because these amide groups are important in the assembly process for the one-component system, the chiral information preset in the dendritic headgroups is not always transcribed into the nanoscale assembly, whereas for the two-component system, fiber formation is always accompanied by chiral ordering because the molecular recognition pathway is completely dependent on hydrogen bond interactions between well-organized chiral dendritic headgroups.
authors.affiliation: Department of Chemistry, University of York, Heslington, York YO10 5DD, UK.
authors.forename: Buqing
authors.initials: B
authors.lastname: Huang
authors.forename: Andrew R
authors.initials: AR
authors.lastname: Hirst
authors.forename: David K
authors.initials: DK
authors.lastname: Smith
authors.forename: Valeria
authors.initials: V
authors.lastname: Castelletto
authors.forename: Ian W
authors.initials: IW
authors.lastname: Hamley