A direct comparison of one- and two-component dendritic self-assembled materials: Elucidating molecular recognition pathways

TY - JOUR

T1 - A direct comparison of one- and two-component dendritic self-assembled materials: Elucidating molecular recognition pathways

AU - Huang, B Q

AU - Hirst, A R

AU - Smith, D K

AU - Castelletto, V

AU - Hamley, I W

PY - 2005/5/18

Y1 - 2005/5/18

N2 - 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.

AB - 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.

KW - 2-DIRECTIONAL CASCADE MOLECULES

KW - GEL-PHASE MATERIALS

KW - ORGANIC-SOLVENTS

KW - L-LYSINE

KW - ASSOCIATION PROPERTIES

KW - PEPTIDIC DENDRIMERS

KW - GELATION PROPERTIES

KW - ROOM-TEMPERATURE

KW - AQUEOUS-SOLUTION

KW - LATENT GELATORS

U2 - 10.1021/ja050412d

DO - 10.1021/ja050412d

M3 - Article

SN - 0002-7863

VL - 127

SP - 7130

EP - 7139

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

IS - 19

ER -