A model zwitterionic surfactant, oleyl amidopropyl betaine (OAPB), that spontaneously forms viscoelastic wormlike micelles in aqueous solution is mixed with a variety of structurally diverse organic additives. By systematically varying the nature of these additives, insight into the effects of their aromaticity and polarity on the bulk assembly and fluid behaviour of these micelles is gained by the complementary use of small-angle neutron scattering and viscosity measurements. Inclusion of non-polar additives causes the wormlike aggregates to transition into microemulsions above a critical additive concentration; the precise partitioning within the micelle is determined using contrast variation. Alternatively, polar additives do not appear to cause evolution from the wormlike structure, but instead influence the fluid rheology, with some serving to significantly increase viscosity above that of the pure surfactant solution. Addition of these molecules is accompanied by an increase in fluid viscosity when the oxygenated group of the additive is resonance stabilised or acidic. This effect is thought to be a result of surfactant–additive synergism, in which charge screening of the surfactant head-groups causes stronger attractions between molecules, increasing the scission energy of the micelles (i.e. reducing their ability to break apart and reform). Further doping of acidic additives past a critical concentration causes phase separation of the wormlike mixtures. According to ultra-small-angle neutron scattering measurements, the incorporation of all additives (polar or non-polar, aromatic or non-aromatic) results in the formation of ‘branched’ wormlike networks. These findings emphasise the significant impact of impurities or additives on the properties of aqueous wormlike micellar systems formed by zwitterionic surfactants, and could also inform selection of solutes for controlling fluid rheology.

将在水溶液中自发形成粘弹性蠕虫状胶束的两性离子表面活性剂模型油性酰胺丙基丙基甜菜碱（OAPB）与多种结构多样的有机添加剂混合。通过系统地改变这些添加剂的性质，可通过小角度中子散射和粘度测量的补充使用，深入了解其芳香性和极性对这些胶束的组装和流体行为的影响。包含非极性添加剂会导致蠕虫状聚集体转变成高于临界添加剂浓度的微乳状液。使用对比度变化确定胶束内的精确分配。另外，极性添加剂似乎不会引起蠕虫状结构的演变，反而会影响流体的流变性，其中一些可显着提高粘度，使其高于纯表面活性剂溶液的粘度。当添加剂的氧化基团被共振稳定或呈酸性时，这些分子的添加伴随着流体粘度的增加。这种作用被认为是表面活性剂-添加剂协同作用的结果，其中表面活性剂头部基团的电荷筛选导致分子之间更强的吸引力，从而增加了胶束的断裂能量（即降低他们分解和改革的能力）。酸性添加剂的进一步掺杂超过临界浓度会引起蠕虫状混合物的相分离。根据超小角中子散射测量，所有添加剂（极性或非极性，芳族或非芳族）的掺入都会形成“分支”蠕虫状网络。这些发现强调了杂质或添加剂对由两性离子表面活性剂形成的水性蠕虫状胶束系统的性能的重大影响，并且还可以为控制流体流变学的溶质选择提供依据。