Zoubeida Ounaies, Ph.D. in Engineering Science and Mechanics in ’95 and Assistant Professor in the Department of Aerospace Engineering at the Texas A&M University will be delivering a seminar on “Active Polymer Nanocomposites: Towards Enhanced Sensing and Actuation Performance.”

The seminar scheduled for Tuesday, January 27, 2009 will begin at 4:00 pm in 135 Reber Building.

In the last two decades, electroactive polymers (EAPs) have gained notoriety as a valuable class of smart materials. Polymers offer the advantage of processing flexibility, lightweight, and durability. Other notable features of polymers include their low dielectric constant, low elastic stiffness, and low density, which may result in a high voltage sensitivity (good sensor characteristics) and low acoustic and mechanical impedance (crucial for medical and underwater applications). Shortfalls of current EAPs however include relatively small electromechanical coupling coefficient, high actuation voltage and poor blocked stress.

In this presentation, we explore nanocomposite concepts to address these materials limitations and enhance the electroactive response of polymers. Our goal is to judiciously control nanoparticle dispersion, distribution, and interfacial interactions to develop polymer nanocomposites with inherent electromechanical coupling. Specifically, the study investigates carbon nanotube, carbon nanofiber and nanoclay-based polymer nanocomposites as electrostrictive and piezoelectric materials. Stable solutions of nanoparticles combined with a series of polymers are prepared and processed into various forms such as films, fibers, and non-woven mats. Electrical and dielectric properties of the resulting nanocomposites are investigated as a function of frequency and volume content.

The dispersion is assessed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Differential Scanning Calorimetery (DSC) is used to study the effect of the nanoparticles on the glass transition temperature, Tg, and in some cases the crystallinity of the resulting nanocomposite. The percolation threshold is computed by using bulk conductivity data and it is found that, in most cases, percolation occurs at about 0.04 to 0.2 vol%.

The interaction between the nanoparticle and the polymer matrix is studied using spectrometry and electron microscopy. Our results indicate that the interface between the nanoparticles and the polymers is a key factor in the observed electromechanical response. Better wetting and interaction between nanoparticle and polar polymers compared to non-polar ones is considered the primary reason for enhanced actuation response in these nanocomposites. We further address the issue of nanoparticle dispersion and distribution by implementing electric field micro-tailoring of carbon nanotubes in liquid and solid polymers.

The anticipated outcome is the development of lightweight, active structural polymer nanocomposites with unique combinations of mechanical, electrical, and coupled properties for use in lightening strike mitigation, EMI shielding, structural health monitoring, and energy harvesting.