An organic-based amphiphilic Janus polymer nanosheet: Synthesis, properties, and microscopic dispersion interpretations

• Organic-based amphiphilic Janus polymer nanosheets are synthesized via sucrose templates. • Colloidal stability and aggregation kinetics of nanosheet suspensions are systematically measured. • Optical microrheology is pioneered to study nanosuspension’s migration behavior for the first time. • AJPN could be used as solid surfactants to reduce oil–water interfacial tension and stabilize emulsions. Due to the distinctive anisotropy in shapes and affluent potential in properties, amphiphilic Janus polymer nanosheets (AJPN) have attracted widespread attention. Low-cost, controllable, and precise functional polymerization remains a great challenge to conventional template methods. Herein, an organic-based AJPN was synthesized with polystyrene as the hydrophobic side and carboxyl groups presented at the hydrophilic side. Sucrose was selected as the adsorption template, which could be removed simply by water-washing. The lateral sizes could be regulated by adjusting the ultrasonic time and power after the precise construction of polymer shells. The colloidal stability and aggregation kinetics of AJPN suspension under different conditions were quantitatively measured. In particular, Rheolaser optical microrheology was pioneered to explore the authentic migration behaviors and rheological properties of AJPN aqueous solution for the first time. The results revealed that AJPN solution presented as thermodynamically unstable solid suspension, which was far different from real solution, emulsion or cross-linked hydrogel formed by common hydrophilic polymers. The carboxyl groups and the steric effect of polymer chains greatly improved the self-stability of AJPN suspension. The influences of microscopic migration of AJPN on their macroscopic dispersion in different stages were concluded, which was closely related to the applicability of nanofluid products in storage, transportation, or performance periods. Moreover, due to the amphiphilic property, Janus nature and lamellar nanomorphology, AJPN could be used as solid surfactants to reduce oil–water interfacial tension and stabilize emulsions. We hope this work can offer more opportunities for the synthesis of AJPN with different chemical compositions, and promote the development of dispersion stability of nanosheets.