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Nanocomposites Research
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Polymer-based nanocomposites

Areas of interest:

  • Electro-spun Polymer Fibers
  • Phase Transitions and Confinement Effects in PVDF Nanocomposites
  • Organically Modified Silicate Nanocomposites
  • Carbon Nanotube Nanocomposites
Erika Cozza
Visiting Scholar, Erika Simona Cozza, from the University of Genoa, Italy, studies X-ray diffraction of PBT/POSS electrospun fibers.

Nanocomposites are, as their name implies, composite materials in which at least one of the ingredients has a size on the nanometer length scale. The Cebe group is involved in studies of the structure and properties of nanocomposites made of two basic ingredients: a semicrystalline polymer host, and an inclusion. Examples of host polymers are: poly(vinylidene fluoride), PVF2, poly(ethylene terephpthalate), PET, and poly(trimethylene terephthalate), PTT. Several types of inclusions are under study: organically modified silicate (OMS), which is a type of clay, and single and multi-walled carbon nanotubes.

Recent studies show that even very small amounts of such inclusions can have a dramatic effect on thermal properties, fire retardancy, mechanical strength, and electric behavior. Initially, the OMS (clay) particles exist as thin, stacked sheets. The best reinforcement occurs when the sheet-like structure is broken up, and the individual clay sheets are dispersed more or less uniformly throughout the polymer host. The complete separation of the stacked OMS sheets is termed "exfoliation". An intermediate level of separation is achieved if some of the polymer host can push its way in between the OMS layers, without separating them fully. This intermediate step is called "intercalation". To provide a high level of separation, our group uses ultrasonication and electro-spinning to disperse the particles.

Nanocomposites have been made in the Cebe research group using LucentiteTM and NanomerTM OMS, as well as single and multi-walled carbon nanotubes as inclusions in semicrystalline polymer hosts. Our group has found that the crystal phase of the polymer host is affected by the amount and type of the inclusion. Low amounts of OMS cause PVF2 polymer to crystallize predominantly into the orthorhombic alpha phase. As the amount of OMS increases, the monoclinic beta phase takes over, and becomes the sole crystal type above about 1% of OMS by weight. Studies of the crystal phase, and quantification of the relative amounts of the alpha and beta phase, are ongoing projects. Dielectric relaxation spectroscopy allows us to monitor the glass transition, crystal relaxation, and interfacial polarization effects in polymer based nanocomposites.

Lei using impedance analyzer
Graduate student, Lei Yu, measures the dielectric properties of PVDF/OMS nanocomposites using an impedance analyzer.
Zhen with 
		 electrospun polymer
Graduate student, Erika Cozza.

Recent efforts involve the formation of semicrystalline polymer membranes using the process of electrospinning. High voltage is applied to a polymer solution using a needle-shaped electrode. The polymer accelerates toward a grounded electrode plate where it is collected as a thin fibrous membrane. Nanocomposite membranes containing either OMS or single walled carbon nanotubes are currently being investigated.

The 2008 intern class made a different type of nanocomposite. They used carbon nanotubes for the additive, keeping the host polymer, PVDF, the same. The carbon nanotubes were mixed into PVDF and the samples were pressed into thin films. Intern Shabnam Razmpour (from RIT) examines the film quality in the upper left picture. Thin strips were cut from the film, and a home-built apparatus, called a zone-drawer, was used to stretch the film at elevated temperature. Luis Fernandez (from RIT) is shown in the upper right picture placing a film into the zone-drawer. Once the film is stretched, its structure is examined by Kyle Edenzon (lower left) using two-dimensional X-ray diffraction, and by Jenna Woodburn (lower right) using infrared spectroscopy.

Shabby examines film
Fernandez with zone drawer
Kyle Edenson
Jenna Woodburn

This program is funded by the National Science Foundation through the Polymers Program of the Division of Materials Research, grant DMR-0704056 and previously through grant DMR-0406127, and by the Petroleum Research Fund of the American Chemical Society, grant 44149-AC7.