Lamellar biogels comprising fluid membranes with a newly synthesized class of polyethylene glycol-surfactants
- Materials Research Laboratory, Materials Department and Physics Department, Biochemistry and Molecular Biology Program, University of California, Santa Barbara, California 93106 (United States)
- Makromolekulare Chemie I and Bayreuther Institut fuer Makromolekuelforschung (BIMF), Universitaet Bayreuth, 95440 Bayreuth (Germany)
A series of four polymer{endash}surfactant macromolecules, each consisting of a double-chain hydrophobic moiety attached onto a monofunctional polyethylene glycol (PEG) polymer chain, were synthesized in order to study their effect upon the fluid lamellar liquid crystalline (L{sub {alpha}}) phase of the dimyristoylphosphatidylcholine/pentanol/water system. The main finding of this study is that the addition of these compounds induces a new lamellar gel, called L{sub {alpha},g}. We have determined the phase diagrams as a function of PEG{endash}surfactant concentration, c{sub PEG}, and weight fraction water, {Phi}{sub W}. All phase diagrams are qualitatively similar and show the existence of the gel. Unlike more common polymer physical gels, this gel can be induced either by increasing c{sub PEG} or by adding water at constant c{sub PEG}. In particular, less polymer is required for gelation as water concentration increases. Moreover, the gel phase is attained at concentrations of PEG{endash}surfactant far below that required for classical polymer gels and is stable at temperatures comparable to the lower critical solution temperature of free PEG{endash}water mixtures. Small angle x-ray experiments demonstrate the lamellar structure of the gel phase, while wide angle x-ray scattering experiments prove that the structure is L{sub {alpha}}, not L{sub {beta}{sup {prime}}} (a common chain-ordered phase which is also a gel). The rheological behavior of the L{sub {alpha},g} phase demonstrates the existence of three dimensional elastic properties. Polarized light microscopy of L{sub {alpha},g} samples reveals that the L{sub {alpha},g} is induced by a proliferation of defect structures, including whispy lines, spherulitic defects, and a nematiclike Schlieren texture. We propose a model of topological defects created by the aggregation of PEG{endash}surfactant into highly curved regions within the membranes. (Abstract Truncated)
- OSTI ID:
- 527998
- Journal Information:
- Journal of Chemical Physics, Vol. 107, Issue 9; Other Information: PBD: Sep 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Lamellar Gels and Spontaneous Vesicles in Catanionic Surfactant Mixtures
Zero Spontaneous Curvature and Its Effects on Lamellar Phase Morphology and Vesicle Size Distributions