Sorbonne Université, Centre National de la Recherche Scientifique, Laboratoire de Chimie de la Matière Condensée de Paris, LCMCP, F-75005 Paris, France.
Soft Matter. 2020 Mar 11;16(10):2528-2539. doi: 10.1039/c9sm02158b.
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.
脂质层状水凝胶是由磷脂层状相而不是纤维状网络组成的罕见软流体。这些材料的机械性能受缺陷控制，这些缺陷是由聚合物或表面活性剂在经典脂质双层中的局部积累引起的。本文报道了一类由发酵得到的单一 bola 形糖基化脂质组成的新型脂质层状水凝胶。脂质自组装成平插的交错膜，由静电斥力稳定，并堆积成微米级的层状畴。从纳米到微米尺度上，膜中的缺陷和层状畴的连接负责水凝胶的弹性性质。通过小角 X 射线和中子散射（SAXS、SANS）结合，探测层状结构，通过偏光显微镜可视化富含缺陷的层状畴，通过振荡流变学研究弹性性质。后者表明，存储模量 G'和损耗模量 G''都以弱幂律频率的形式变化，可以用分数流变学模型拟合。水凝胶具有流变稀释特性和二次恢复。我们还表明，离子强度不仅如预期的那样是控制层状相中相互作用所必需的，而且最重要的是，它直接控制层状凝胶的弹性性质。
