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Herein, a zwitterionic Gemini VES (named VES-C) with double ultra-long hydrophobic tails was designed and synthesized which aimed to construct WLM net-structures in high-salinity aqueous solution. Due to the carboxylic group on the spacer, it exhibits partial carboxyl betaine properties and performs well in high salinity environment. Molecular dynamic simulation was carried out and RDF curves were analyzed to predict and explain the mechanism of salinity tolerance of VES-C. Compared with cationic Gemini VESs, a series of experiments were conducted by varying salinity, including surface tension, DLS, 1H NMR and fluorescent probe, to explain the salt-tolerance mechanism of VES-C. The salinity cloudy point of VES-C surpasses 10 wt%, exhibiting superior salt-tolerance to those cationic Gemini VESs. Trough viscosity measurement, oscillatory measurement and microstructure observation, it proves that VES-C molecules can construct WLM netlike structures within the salinity range from 3 wt% to 10 wt% (optimal salinity: 4 wt%), thus VES-C can be applied as the clean thickener to prepared seawater or brine based fracturing fluid by constructing WLM netlike structure in high salinity aqueous environment, which leaves the preparation of clean fracturing fluid independent of freshwater resources.

Supramolecular linear polyacrylamide (SL-PAM) was prepared by host–guest interaction of β-cyclodextrin (β-CD) dimmer and adamantane-terminated polyacrylamide (AT-PAM). The β-CD dimmer was synthesized by mono 6-deoxytosyl-β-cyclodextrin and p-phenylenediamine. AT-PAM was prepared by reversible addition-fragmentation chain transfer radical polymerization (RAFT) using the adamantane-terminated trithiocarbonate (ATT) as chain transfer agent. The structures of β-CD dimmer and AT-PAM were determined by 1H NMR. 2D NOESY NMR and thermal analysis of SL-PAM sample were carried out to validate the formation of the inclusion complex. The salt tolerance and temperature resistance of SL-PAM were also investigated. Compared with polyacrylamide, the temperature resistance of SL-PAM has no obvious advantage, but salt tolerance of SL-PAM is good within a certain range of salinity.