title: Thixotropic twin-dendritic organogelators.
abstract: Twin-dendritic organogelators have been prepared through selective functionalization of N-(3-aminopropyl)-1,3-propanediamine (APPDA) with self-assembling dendrons by using 1,1'-carbonyldiimidazole (CDI). Subsequent modification of the APPDA linker provided an additional degree of structural diversity by which to tailor the gelator self-assembly in bulk or in the gel state. These compounds are able to gel cyclohexane, toluene, n-butyl acetate, ethyl acetate, dichloromethane, and tetrahydrofuran. 3,4-Disubstituted apical branching units provided the most efficient organogelators and show a propensity to form thixotropic gels, wherein the gel recovers its elasticity after being subjected to shear. Structural and retrostructural analysis of the twin-dendritic organogelators reveals the bulk structural characteristics to be indicative of the subsequent gel properties. Diverse self-organized arrays were identified in bulk and all are able to form gels, thus indicating the role of quasiequivalence in mediating self-assembly in the gel state. Furthermore, we have found that porous columnar mesophases provide a strategy by which to prepare thixotropic gels. We demonstrate the importance of weak lateral hydrogen bonding within a column stratum versus hydrogen bonding along the length of the column for forming porous columnar mesophases and, by extension, thixotropic gels.
authors.affiliation: Roy & Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA. percec@sas.upenn.edu
authors.forename: Virgil
authors.initials: V
authors.lastname: Percec
authors.forename: Mihai
authors.initials: M
authors.lastname: Peterca
authors.forename: Michael E
authors.initials: ME
authors.lastname: Yurchenko
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Rudick
authors.forename: Paul A
authors.initials: PA
authors.lastname: Heiney
mesh_terms: D018360:Crystallography, X-Ray; D050091:Dendrimers / Q000138:chemical synthesis / Q000737:chemistry*; D003959:Diamines / Q000737:chemistry*; D005782:Gels; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011407:Propane / Q000031:analogs & derivatives* / Q000737:chemistry; D014783:Viscosity
chemical_list: D050091:Dendrimers; D003959:Diamines; D005782:Gels; D007093:Imidazoles; C527934:N-(3-aminopropyl)-1,3-propanediamine; C006900:N,N-carbonyldiimidazole; D011407:Propane