Dale W. Schaefer, Jian Zhao Department of Materials Science and Engineering University of Cincinnati Cincinnati, OH Janis Brown, Dave Anderson, Max Alexander, Liz Donaldson, Lindsay Richardson and Jeff Baur Air Force Research Laboratory Dayton, Ohio Jan Ilavsky National Institutes of Standards and Technology UNICAT Advanced Photon Source Argonne National Laboratory, 9700 South Cass Avenue Argonne, IL Hierarchical Structure of Carbon Nanotubes and Nanofibers

Multi-walled Nanofibers Single-walled Nanotubes 300 nm TEM comparing MWNFs (left) and SWNTs (right). Note the branched polymer character of the SWNTs. The SWNTs are clustered into “ropes” that are not disrupted upon water suspension. Images are from Air Force Research Laboratory (AFRL). MWNFSWNT

Scattering from Nanotubes 3000 Å

Short-Scale Structure (dried suspension) Hard Particle Diameter = 2.4 x R G = 4.3 nm= 43 Å Too small? As Received (dirty)

ASI Nanofibers 1.2 µ Light Light +USAXS+SAXS Surface roughness?

Large-Scale Structure of Suspended SWNTs and MWNFs Comparison of Small-angle Light scattering from nanotubes and nanofibers.Dispersing agents of PMAA, PSSO3 and PAAHCl were used to assist dispersion in water. SWNT Fractal StructureMWNF Rod-like Structure

SWNT Aggregates are Very Robust Reciprocal space data on SWNTs dispersed in water with polystyrene sulfonate and polymethylacrylic acid.. The data is from a Micromeritics Digisizer. Sonication has little effect on Large Scale Structure of SWNTs

Stress-Strain Data SWNT/PU

Dynamic Mechanical Properties Strain Softening

Loading Dependence (MWNTs in PU) Modulus Loss AlignDe network

Dispersion Strategies: Polyelectrolyte coatings Generic Colloid

Nanofiber -Polyelectrolyte Dispersion in PU

Mechanical Properties of Coated Nanofiber/PU Composites Comparison of DMA data from uncoated, one layer and two layers coated 15wt% nanotubes PU films. The loss as Tan delta (lower three curves) is plotted on the right axis. The legend in the figure indicates the strain sweep sequence. These samples were all swept three times.