title: Influence of the solvent and the enantiomeric purity on the transition between different supramolecular polymers.
abstract: The self-assembly of two enantiomerically pure hexa(oligo(p-phenylene vinylene))-substituted benzenes having 24 stereocenters was studied in pure methylcyclohexane (MCH) and in a mixture of MCH/toluene (4:1). Irrespective of the solvent a cooperative supramolecular polymerization mechanism was determined for these star-shaped molecules by using temperature-dependent CD and UV/Vis spectroscopy. Quite remarkably, a transition from one helical supramolecular state (A) to a second more thermodynamically stable supramolecular helical assembly (B) was observed. The rate of the A→B transition was strongly dependent on the nature of the solvent; being faster in the solvent mixture than in pure MCH. By using size exclusion chromatography we could relate the increased rate to a decreased stability of the supramolecular A state in the solvent mixture. Next, we mixed the two enantiomerically pure hexa-substituted benzene derivatives in a so-called majority-rules experiment, which lead to the anitcipated chiral amplification in the A state. More importantly it appeared that the A→B transition was significantly hampered in these mixed systems. Furthermore, the absence of chiral amplification in the B state revealed the formation of separated enantiomerically pure assemblies. Therefore, by using a wide variety of spectroscopic and chromatographic techniques we determined the influence of solvent and enantiomeric purity on the transition between different supramolecular states.
authors.affiliation: Institute for Complex Molecular Systems and the Laboratory of Macromolecular and Organic Chemistry, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Martin
authors.initials: M
authors.lastname: Wolffs
authors.forename: Juliën L J
authors.initials: JL
authors.lastname: van Velthoven
authors.forename: Xianwen
authors.initials: X
authors.lastname: Lou
authors.forename: Ralf A A
authors.initials: RA
authors.lastname: Bovee
authors.forename: Maarten
authors.initials: M
authors.lastname: Pouderoijen
authors.forename: Joost L J
authors.initials: JL
authors.lastname: van Dongen
authors.forename: Albertus P H J
authors.initials: AP
authors.lastname: Schenning
authors.forename: E W
authors.initials: EW
authors.lastname: Meijer
mesh_terms: D046911:Macromolecular Substances / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D058105:Polymerization; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013237:Stereoisomerism; D013816:Thermodynamics
chemical_list: D046911:Macromolecular Substances; D011108:Polymers; D012997:Solvents