Dynamic, hollow nanotubular networks with superadjustable pH-responsive and temperature resistant rheological characteristics

Recently, the interest in stimuli-responsive and adaptable materials has continuously grown in various fields and applications. For such responsive systems, different triggers, including pH, light, pressure, temperature, and electric field, have been utilized to control dynamics and assembly. Among these, pH is one of the most convenient, energy-efficient, and economic modalities. Besides, plenty of traditional materials have poor thermal and salt stability, limiting their applications. Herein, we report a new design of a pH-responsive viscoelastic supramolecular complex (VSC) based on commplexation of a new long-chain amino-amide and maleic acid. The system demonstrated a sol-gel-sol transition from pH 2 to 10, with the largest static viscosity occurring at pH 6 (similar to 1000 Pa.$) and the smallest viscosity at pH 4 (similar to 3.3 Pa.$), indicating similar to 300-fold control over the viscosity. For a given concentration, the static viscosity of VSC was about 15 times larger than that of CTAB/NaSal, a well-established dynamic viscoelastic system, and no pH-responsiveness was observed for the traditional system. In addition, the VSC demonstrated a superior temperature tolerance and lower temperature dependence. The potential of these intriguing dynamics viscoelastic systems was evaluated for hydraulic fracturing and enhanced oil recovery applications. Proppant settling velocity of DMAA/MA was 500 similar to 1000 times lower than that of CTAB/NaSal and common traditional polymers. Likewise, the oil recovery percentage could be significantly improved with the utilization of DMAA/MA compared to the CTAB/NaSal (86 % vs 52 %). Aside from applications in hydraulic fracturing and enhanced oil recovery, we anticipate that the intriguing rheological properties of this viscoelastic system can be beneficial for other chemical engineering applications including personal care products, cosmetics, lubricants, and biomedical gels.

Automated summary

Recently, there has been a growing interest in stimuli-responsive and adaptable materials in various fields and applications. This paper reports the design of a pH-responsive viscoelastic supramolecular complex (VSC) based on the complexation of a new long-chain amino-amide and maleic acid. The VSC demonstrated a sol-gel-sol transition from pH 2 to 10 and showed potential applications in hydraulic fracturing and enhanced oil recovery due to its superior temperature tolerance and viscosity control.