title: Bolalipid fiber aggregation can be modulated by the introduction of sulfur atoms into the spacer chains.
abstract: The aggregation behavior in aqueous suspension of two symmetrical single-chain bolaamphiphiles, namely 12,21-dithiadotriacontane-1,32-diyl-bis [2-(tri-methylammonio)ethylphosphate] (PC-C32SS-PC) and 12,21-dithiadotriacontane-1,32-diyl-bis[2-(dimethylammonio)ethylphosphate] (Me(2)PE-C32SS-Me(2)PE), containing sulfur as heteroatoms in the chains, was studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FT-IR), small angle neutron scattering (SANS), and transmission electron microscopy (TEM). The rheological properties of hydrogels formed by the aggregation into nanofibers were studied by oscillatory rheology. Based on the well-characterized behavior of bolalipids with long alkyl chains which at room temperature can form a network of nanofibers leading to the formation of a hydrogel, we investigated whether the incorporation of two heteroatoms of sulfur into the spacer chain of the molecules has an influence on the aggregation properties. Compared to the analogues without sulfur, the fibrous aggregates formed by sulfur containing compounds are less stable and build weaker viscoelastic gels. This is due to a perturbation of the packing of the chains as the sulfur atoms change the bond angle in the chain compared to the molecules with pure alkyl chains leading to kinks in the chain. For the bolaamphiphile with the Me(2)PE headgroups this effect is less pronounced due to the possibility of forming stabilizing hydrogen bonds between the headgroups.
authors.affiliation: Institute of Chemistry, Physical Chemistry, MLU Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle, Germany.
authors.forename: Gesche
authors.initials: G
authors.lastname: Graf
authors.forename: Simon
authors.initials: S
authors.lastname: Drescher
authors.forename: Annette
authors.initials: A
authors.lastname: Meister
authors.forename: Vasyl M
authors.initials: VM
authors.lastname: Haramus
authors.forename: Bodo
authors.initials: B
authors.lastname: Dobner
authors.forename: Alfred
authors.initials: A
authors.lastname: Blume
mesh_terms: D008958:Models, Molecular; D015394:Molecular Structure; D010755:Organophosphates / Q000737:chemistry*; D010316:Particle Size; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D010755:Organophosphates; D000644:Quaternary Ammonium Compounds; D013455:Sulfur