School of Chemistry, Monash University, Clayton 3800, Australia.
Phys Chem Chem Phys. 2018 Jun 20;20(24):16592-16603. doi: 10.1039/c8cp02101e.
Lamellar liquid crystals comprising oil, water and surfactant(s) were formulated and analysed in order to examine how these materials responded to the inclusion of inorganic nanoparticles, in terms of their structural and rheological characteristics. Lamellar phases were formed from mixtures of water, para-xylene and Triton X-100, and analysis was performed via small-angle neutron scattering (SANS), polarising light microscopy (PLM), and amplitude and viscosity sweeps. The partial replacement of Triton X-100 with oleic acid appeared to cause an increase in bilayer thickness, attributed to less efficient packing of the different molecules. Addition of oleic acid also appeared to cause both a loss in lamellar repeat ordering, attributed to heterogeneity of the bilayers, and a rise in long range order, potentially caused by the stiffer bilayers. Adding silica nanoparticles of different size and surface chemistry caused a stiffening of the samples at the expense of a longer-range lamellar repeat order. This strengthening is attributed to aggregation at the domain boundaries, and it was found that hydrophobic particles tended to form stronger aggregates while for larger particles (20 nm as opposed to 10 nm) aggregation was apparently reversible. These results give a more comprehensive understanding of how to reliably control the structural and rheological properties of lamellar liquid crystals, and emphasise the importance of the size and surface chemistry of any inclusions, for applications in cosmetics, drug delivery, and microfluidics.
为了研究这些材料在包含无机纳米粒子时如何响应，我们制备并分析了包含油、水和表面活性剂的层状液晶。层状相由水、对二甲苯和 Triton X-100 的混合物形成，并通过小角中子散射（SANS）、偏光显微镜（PLM）以及幅度和粘度扫描进行分析。用油酸部分替代 Triton X-100 似乎会导致双层厚度增加，这归因于不同分子的包装效率降低。油酸的添加似乎还会导致层状重复有序性丧失，这归因于双层的不均匀性，以及长程有序性上升，这可能是由于双层变硬所致。添加不同尺寸和表面化学性质的二氧化硅纳米粒子会使样品变硬，而层状重复有序性变长。这种强化归因于畴界处的聚集，并且发现疏水性颗粒往往会形成更强的聚集体，而对于较大的颗粒（20nm 而不是 10nm），聚集显然是可逆的。这些结果更全面地了解了如何可靠地控制层状液晶的结构和流变性质，并强调了任何包含物的尺寸和表面化学性质的重要性，适用于化妆品、药物输送和微流控等应用。
