Patnarin Worajittiphon

Locking carbon nanotubes in confined lattice geometries--a route to low percolation in conducting composites.

A significant reduction in the electrical percolation threshold is achieved by locking carbon nanotubes (CNTs) in a predominantly hexagonally close-packed (HCP) colloidal crystal lattice of partially plasticized latex particles. Contrary to other widely used latex processing where CNTs are randomly distributed within the latex matrix, for the first time, we show that excluding CNTs from occupying the interior volume of the latex particles promotes the formation of a nonrandom segregated network. The electrical percolation threshold is four times lower in an ordered segregated network made with colloidal particles near their glass transition temperature (T(g)) in comparison to in a random network made with particles at a temperature well above the T(g). This method allows for a highly reproducible way to fabricate robust, stretchable, and electrically conducting thin films with significantly improved transparency and lattice percolation at a very low CNT inclusion which may find applications in flexible and stretchable electronics as well as other stretchable technologies. For instance, our technology is particularly apt for touch screen applications, where one needs homogeneous distribution of the conductive filler throughout the matrix.

Colloid-Assisted Self-Assembly of Robust, Three-Dimensional Networks of Carbon Nanotubes over Large Areas

Natural materials, such as bone and spider silk, possess remarkable properties as a result of sophisticated nanoscale structuring. They have inspired the design of synthetic materials whose structure at the nanoscale is carefully engineered or where nanoparticles, such as rods or wires, are self-assembled. Although much work has been done in recent years to create ordered structures using diblock copolymers and template-assisted assembly, no reports describe highly ordered, three-dimensional nanotube arrays within a polymeric material. There are only reports of two-dimensional network structures and structures on micrometer-size scales. Here, we describe an approach that uses plasticized colloidal particles as a template for the self-assembly of carbon nanotubes (CNTs) into ordered, three-dimensional networks. The nanocomposites can be strained by over 200% and still retain high conductivity when relaxed. The method is potentially general and so may find applications in areas such as sensing, photonics, and functional composites.

Enhanced Thermal Actuation in Thin Polymer Films Through Particle Nano‐Squeezing by Carbon Nanotube Belts

The continuous development of nanoscale electronic, sensing, and actuating devices requires researchers and manufactures to devise new methods to design materials with nanoscale features and ultimately with projected improvement in performance. The extraordinary mechanical and electronic properties of carbon nanotubes (CNTs) have attracted widespread interest for a range of applications. CNTs exhibit a very low linear expansion coeffi cient, α , (on the order of the α of diamond, ca. 1.1 × 10 − 6 K − 1 ) and a uniquely high thermal conductivity along their longitudinal axis. [ 1 , 2 ] In contrast to CNTs, polymers generally have a higher α , which is dependent on temperature. In amorphous polymers, there are two distinct regions of expansivity with different values of thermal expansion: the glassy (lower α ) and rubbery (higher α ) regions, separated by a phase transition at the glass transition temperature ( T g ). [ 3 ] Furthermore, the α of polymers can be drastically varied by reinforcement with microfi bers, CNTs, and, more recently, graphene oxide sheets. [ 4–6 ]

Stretchable Conductive Networks of Carbon Nanotubes Using Plasticized Colloidal Templates

We present a study of the behavior of highly ordered, segregated single-wall carbon nanotube networks under applied strain. Polymer latex templates induce self-assembly of carbon nanotubes into hexagonal (2D) and honeycomb (3D) networks within the matrix. Using mechanical and spectroscopic analysis, we have studied the strain transfer mechanisms between the carbon nanotube network and the polymer matrix. Axial deformation of the nanotube network under applied strain is indicated by downshifts in the 2D mode in the Raman spectra, as well as variation in the Radial Breathing modes. The slippage within nanotube bundles at high strain is indicated by a reduction in the 2D mode rate of change. The fractional resistance change of the composites with strain obeys power law dependence. We present a model for the behavior of carbon nanotube bundles under strain informed by these measurements, and potential applications for such composite materials in elastic electronic devices that can tolerate high strain.