Fast and reversible microscale formation of columns in carbon nanotube suspensions

Abstract

Homogeneous carbon nanotube suspensions are studied in the semidilute regime, which is permitted by the use of an effective polysiloxane surfactant, PySi70, as a liquid matrix. We study such suspensions under an AC electric field by optical microscopy, transient light transmission and impedance spectroscopy. Optical microscopy shows the formation of long-range microscale columnar order as a result of a fast field-induced phase separation. The aggregation process is found to be reversible and repeatable, with nanotubes re-dispersing into a homogeneous solution, in a diffusive manner, in the seconds following removal of the electric field. The suggested role of the induced dipolar forces is consistent with the relatively fast columnar formation and characteristic concentration of maximum field-response. The equilibrium columnar structure provides fast field-induced control of the transparency and dielectric response, while avoiding electrical breakdown.

Crystallization of isotactic polypropylene inside dense networks of carbon nanofillers

“…Polymeric composites based on carbon nanotubes (CNTs) and graphene nanosheets (GNSs), because of their outstanding physical and mechanical properties, have attracted increasing attention . It has been found that many physical behaviors of the polymer matrix, such as the glass transition, phase separation, and crystallization, are dramatically altered through the incorporation of carbon nanofillers, which eventually have a significant influence on the properties of the ultimate composites, that is, the mechanical properties, thermal conductivity, and electromagnetic shielding properties . In addition, the structural characteristics of CNTs and GNSs and their physical interactions originating from their high aspect ratios and high specific surface areas are closely related to the phase behaviors and properties of carbon nanofiller/polymer composites …”