Fig.1

Synthesis routes toward preparation of ultralong-chain ionic surfactants"

Fig.2

Krafft point （TK） plotted as a function of molar ratio of hydrotropic salt to NaOEr, CS/CD, where CD is fixed at 1 wt%. Photographs A and B, corresponding to the same sample at CS/CD = 3 of the NaOEr-BTAB system, represent the typical clear micellar solution above TK and crystals below TK, respectively"

Fig.3

Effects of chain length and NaCl addition on the solubility of amidosulfobetaine surfactants [14]:（A） Effect of NaCl concentration on the Krafft temperature of long-chain amidosulfobetaines n-DAS （n = 18, 20, 22, and 24） ;（B） Schematic illustration of the sharp decrease in the Krafft temperature of long-chain amidosulfobetaines induced by a small amount of added salt;（C） Plot of the Krafft temperature （TK） of n-DAS versus surfactant tail length （n） in 3 000 mmol/L NaCl aqueous solution. Effects of chain length and NaCl addition on the solubility of amidocarboxybetaine surfactants [16] :（D） Effect of NaCl concentration on the TK of long-chain carboxybetaines CnDAB （n = 18, 20, 22, and 24） ;（E） Schematic illustration of the possible structures of ultra-long-chain carboxybetaines in aqueous solution"

Fig.4

Steady rheology of the NaOEr-BTAB system at different BTAB concentrations （NaOEr concentration: 70 mmol/L）"

Fig.5

Effect of organic salt concentration on （A） zero-shear viscosity （η0） and （B） plateau modulus （G0） and relaxation time （τR） at 50 ℃ for NaOEr-BTAB and NaOEr-TMAB systems. The NaOEr concentration is fixed at 70 mmol/L"

Fig.6

Effect of temperature on the steady and dynamic rheology of the 70 mmol/L NaOEr + 70 mmol/L BTAB system （insets: Arrhenius plots of η0 and τR）"

Fig.7

Shear viscosity and dynamic viscoelasticity of 250 mmol/L EDAI solution at 30 ℃"

Fig.8

Temperature （A） - and time-dependent （B） apparent viscosity of EDAB and EDPA systems in 20 wt% HCl"

Fig.9

（A） Shear viscosity （η） of 100 mmol/L n-DAS solutions at 80 ℃ as a function of shear rate （$ \dot{\gamma}$）. Influence of pH on rheological behaviours of EMAO solution at 30 ℃.（B） Steady rheology and （C） zero-shear viscosity versus pH curve. Steady-shear rheology and zero-shear viscosity of 0.5 wt% C22AO in EG-water （50/50, v/v）[18]. Steady-shear viscosity versus shear rate at differen temperatures for samples at （D） pH 2.0, （E） pH 6.8, and （F） pH 13.0[19]"

Fig.10

Performances evaluation of EDAB cryo-VES fluid containing GL when employed as an aircraft deicing/anti-icing fluid and an anti-icing clear fracturing fluid [21].（A） A 30 mmol/L EDAB VES fluid with 50 vol% EG attached to a glass substrate with ~ 30 ℃ inclination upon temperature increase from -20 to 20 ℃. With rising temperature, the fluid viscosity declines, and the fluid ultimately drains off the substrate.（B） Proppant-suspending capability of the 60 mmol/L EDAB fluid at 60 and 90 ℃.（C） Flow behaviour of ceramsite dispersed in the 60 mmol/L EDAB fluid at -20 ℃.（D） Gel breaking of 60 mmol/L EDAB fluid with ceramsite using 2-ethyl-1-hexanol as a breaker at 20 ℃"