Self-Assembled Polymeric Nanofibers as “Smart” Thermoresponsive Viscosity Modifiers

Thermoresponsive polymer nanofibers are promising candidates for viscosity modifiers in various applications such as oil lubricants and thixotropic agents, offering great control over fluid behavior in response to temperature via the reversible glass transition of the nanofibers. In this study, thermoresponsive polymer nanofibers with diameters of 40–60 nm are synthesized using styrene and butyl acrylate as core-forming blocks via reversible addition–fragmentation chain transfer (RAFT) aqueous emulsion polymerization. It is found that the thermoresponsivity is governed by the glass-transition temperature (Tg) of the nanofibers, which can be finely tuned via the composition of the nanofibers. The nanofibers are prepared by the self-assembly of amphiphilic block copolymers, and the Tg can be varied between −53 and 100 °C by simply adjusting the monomer ratio. Aqueous dispersions of the nanofibers exhibit reversible viscosity change (by more than an order of magnitude) in response to temperature without morphology disintegration. Consequently, these nanofibers can achieve the desired effect at lower concentrations, making them highly promising as viscosity modifiers.