1. Materials Characterization in Polymer/CNT Fibers using Raman Spectroscopy
Lindsey Thomson
Advisor: Dr. Satish Kumar
Project Mentor: Bradley Newcomb
Conclusions
Acknowledgements
I wish to thank Dr. Satish Kumar for accepting me onto his
research team and his support as my faculty advisor, and Dr.
Fred Cook for his advice and encouragement during my
undergraduate research. Special thanks to Brad Newcomb for
his guidance, patience, and assistance as my project mentor.
Introduction
Resonance Raman Spectroscopy (RRS) was used
to determine CNT chiralities of single-walled
(SWNT) and few-walled carbon nanotubes (FWNT).
An incident laser (λ = 785 nm, E = 1.58 eV) was
used, which allowed for the determination of SWNT
and FWNT chiralities in CNT powders and
PVA/SWNT, PAN/SWNT, and PAN,FWNT gel spun
composite fibers. Frequency shifts of the ωrbm peak
positions and intensity shifts were observed after
preparing the composite polymer/CNT fibers. ωrbm
frequency shifts were attributed to the surrounding
polymeric material (environmental effect), while
intensity shifts (up or down) are attributed to
differences in the bundling state of the CNTs within
the polymeric/CNT fibers as compared to the as-
received CNT. Stress transfer by single filament
straining of polyacrylonitrile/ carbon nanotube
(PAN/CNT) and polyvinyl alcohol/carbon nanotube
(PVA/CNT) fibers was observed by monitoring G
mode downshifts as a function of fiber strain.
Changes in energy band gap also occur, allowing
for the precise determination of SWNT chiralites.
Bundling Effects in Polymer/CNT Fibers
5 nm
GT PAN CF
𝛥𝐸𝑔𝑎𝑝 = 𝑠𝑔𝑛 2𝑛 + 𝑝 3𝑡 𝑜 [ 1 + 𝑣 σ cos 3𝜃 + 𝛾 sin 3𝜃 ]
Best fit line
• Type of polymer and type of CNT effect the
environmental coefficient
• Same chiralities are present in the fiber as in the
powder, but with an upshift in peak position
• Bundling changes the electronic transition energy
of CNTs
Table of Peak Position, Chiralities, and Diameter
Straining Effects in Polymer/CNT
Fibers
• High intensity peaks have ΔE value approaching 0
• ΔE is the difference between laser’s energy and ECNT
• High intensity in (10,2) peak represents a bundled state
• ΔE moves farther off resonance from laser when the (10,2)
peak is debundled
• Debundled CNTs can improve mechanical and electrical
properties of polymer/CNT composites
• Vertical shift due to bundling effect
• Horizontal shift due to environmental effect
Raman Spectroscopy
O'Connell, M. J.; Sivaram, S.; Doorn, S. K., Near-infrared resonance Raman excitation profile studies of single-walled carbon nanotube
intertube interactions: A direct comparison of bundled and individually dispersed HiPco nanotubes. Physical Review B 2004, 69 (23).
• Horizontal shifts of G mode due to straining along
axial direction
• G peak shifts left because stretching/straining
weakens the C-C bond
• Shift in G peak shows that the CNT within the fiber
is being strained, not just polymer sliding past the
CNT as the fiber is strained
Future Work/ Application
• Industry: use Raman to monitor bundling behavior
of CNTs on a systems line
• Control over changes in energy band gap for use
in tunable electronic devices