title: Oligomer-to-polymer transition in short ethylene glycol chains connected to mobile hydrophobic anchors.
abstract: We studied the structure of short ethylene glycol (EG) chains with N repeating units (EGN, N = 3, 6, 9, 12, and 15) connected to hydrophobic dihexadecyl chains by means of a combination of differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS). These synthetic amphiphiles dispersed in water form planar lamellar stacks and hexagonal cylinders confining the EG chains to restricted geometries. Owing to the self-assembly of the anchoring points, the lateral density of EG chains in planar lamella can be quantitatively controlled. Furthermore, the chain-melting phase transition of the anchors enables us to "switch" the intermolecular distance reversibly. SAXS/WAXS results suggest that the shorter EG chains (N = 3, 6, and 9) assume a helical conformation in stacks of planar lamella. When the EG chains are further elongated (N = 12 and 15), the lamellar periodicities cannot be explained by a linear extrapolation of shorter oligomers, but can be interpreted well as polymer brushes following the scaling theorem. Such rich phase behaviors of EGN molecules can be used as a simple model of oligo/poly-saccharide chains on cell surfaces, which act not only as flexible repellers between neighboring cells but also as stable spacers for functional ligands.
authors.affiliation: Lehrstuhl für Biophysik, Technische Universität München, 85748 Garching, Germany. mtanaka@ph.tum.de
authors.forename: Motomu
authors.initials: M
authors.lastname: Tanaka
authors.forename: Florian
authors.initials: F
authors.lastname: Rehfeldt
authors.forename: Matthias F
authors.initials: MF
authors.lastname: Schneider
authors.forename: Christian
authors.initials: C
authors.lastname: Gege
authors.forename: Richard R
authors.initials: RR
authors.lastname: Schmidt
authors.forename: Sérgio S
authors.initials: SS
authors.lastname: Funari
mesh_terms: D002152:Calorimetry, Differential Scanning; D019277:Entropy; D019855:Ethylene Glycol / Q000737:chemistry; D006358:Hot Temperature; D046911:Macromolecular Substances; D008956:Models, Chemical; D008968:Molecular Conformation; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry; D011108:Polymers / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry; D012542:Scattering, Radiation; D013499:Surface Properties; D013696:Temperature; D013816:Thermodynamics; D014965:X-Rays
chemical_list: D046911:Macromolecular Substances; D011108:Polymers; D011134:Polysaccharides; D011092:Polyethylene Glycols; D019855:Ethylene Glycol