  Lipid lamellar hydrogels are rare soft fluids composed of a phospholipid
lamellar phase instead of fibrillar networks. The mechanical properties of
these materials are controlled by defects, induced by local accumulation of a
polymer or surfactant in a classical lipid bilayer. Herein we report a new
class of lipid lamellar hydrogels composed of one single bolaform glycosylated
lipid obtained by fermentation. The lipid is self-organized into flat
interdigitated membranes, stabilized by electrostatic repulsive forces and
stacked in micrometer-sized lamellar domains. The defects in the membranes and
the interconnection of the lamellar domains are responsible, from the nano- to
the micrometer scales, for the elastic properties of the hydrogels. The
lamellar structure is probed by combining small angle x-ray and neutron
scattering (SAXS, SANS), the defect-rich lamellar domains are visualized by
polarized light microscopy while the elastic properties are studied by
oscillatory rheology. The latter show that both storage G' and loss G'' moduli
scale as a weak power-law of the frequency, that can be fitted with fractional
rheology models. The hydrogels possess rheo-thinning properties with
second-scale recovery. We also show that ionic strength is not only necessary,
as one could expect, to control the interactions in the lamellar phase but,
most importantly, it directly controls the elastic properties of the lamellar
gels.
