title: Supramolecular structural diversity among first-generation hybrid dendrimers and twin dendrons.
abstract: Hybrid dendrimers, obtained by complete monofunctionalization of the peripheral amines of a "zero-generation" polyethyleneimine dendrimer, provide structurally diverse lamellar, columnar, and cubic self-organized lattices that are less readily available from other modified dendritic structures. The reaction of tris(2-aminoethyl)amine (TREN) with 4-dodecyloxybenzimidazolide provides only the corresponding zero-generation TREN dendrimer. From the mixture of tri- and disubstituted TREN derivatives obtained from first-generation self-assembling dendritic imidazolides, the hybrid dendrimer and a twin dendron could be separated, purified, and characterized. The hybrid dendrimers display smectic, columnar hexagonal (Phi(h)), and cubic (Pm_3n) lattices. The TREN twin dendrons, on which only two peripheral amines have been acylated, exhibit centered-rectangular columnar (Phi(r-c)), Phi(h), and Pm_3n lattices. The existence of a thermoreversible Phi(h)-to-Pm_3n phase transition in the first-generation hybrid dendrimers and twin dendrons is exploited to elucidate an epitaxial relationship between the two mesophases. We postulate a mechanism by which the transition proceeds. The thermoreversible Phi(h)-to-Pm_3n phase change is accompanied by optical property changes that are suitable for rudimentary signaling or logic functions. This structural diversity reflects the quasiequivalence of flat-taper and conical self-assembling dendrons and the ability of flexible dendrimers to accommodate concomitant conformational and shape changes.
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: Jonathan G
authors.initials: JG
authors.lastname: Rudick
authors.forename: Mihai
authors.initials: M
authors.lastname: Peterca
authors.forename: Michael E
authors.initials: ME
authors.lastname: Yurchenko
authors.forename: Jan
authors.initials: J
authors.lastname: Smidrkal
authors.forename: Paul A
authors.initials: PA
authors.lastname: Heiney
mesh_terms: D050091:Dendrimers / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014961:X-Ray Diffraction
chemical_list: D050091:Dendrimers