PHYSIK-DEPARTMENT



Chemical modification of carbon nanotubes
for nanocomposite applications

Dissertation
von

Anastasia A. Golosova


TECHNISCHE UNIVERSITÄT
ÜNCHEN M TECHNISCHE UNIVERSITÄT MÜNCHEN
Fachgebiet Physik weicher Materie




Chemical modification of carbon nanotubes
for nanocomposite applications

Anastasia A. Golosova



Vollständiger Abdruck der von der Fakultät für Physik der Technischen Universität
München zur Erlangung des akademischen Grades eines
Doktors der Naturwissenschaften (Dr. rer. nat.)
genehmigten Dissertation.


Vorsitzender: Univ.-Prof. Dr. Ralf Metzler
Prüfer der Dissertation: 1. Univ.-Prof. Christine M. Papadakis, Ph.D.
2. Univ.-Prof. Dr. Rainer Jordan, Technische Universität Dresden



Die Dissertation wurde am …12.07.2011… bei der Technischen Universität München
eingereicht und durch die Fakultät für Physik am …25.07.2011… angenommen.
Great difficulties are felt at first [in research] and these cannot be
overcome except by starting from experiments … and then by conceiving
certain hypotheses … But even so, very much hard work remains to be done
and one needs not only great perspicacity but often a degree of good fortune.
(Huygens)




Preface 

The present dissertation is the result of the project “Functional nanocomposites by directed
assembly”, funded by International Graduate School of Science and Engineering (IGSSE).
IGSSE is a scientific institution of TU München that offers an interdisciplinary and team-
oriented approach to a research. The present work is not an exception. The goals of the
project could only be obtained in close collaboration between polymer chemistry, polymer
physics and materials engineering. The chemical modification of the carbon nanotubes and
its characterization was carried out in the WACKER-Lehrstuhl für Makromolekulare
Chemie, TU München, whereas analysis of the carbon nanotubes’ dispersions in the
Fachegebiet Physik weicher Materie, Physikdepartment, TU München. The preparation and
characterization of the carbon nanotubes/block copolymer nanocomposites was performed
during a three-months research stay at the DTU Nanotech, Technical University of
Denmark.




Abstract 

Nanocomposites from carbon nanotubes (CNTs) and anisotropic, nanostructured block
copolymers are expected to have anisotropic mechanical and electrical properties.
However, for efficient incorporation of CNTs into a polymer matrix, a chemical
functionalization of CNTs is required; also, a thorough characterization of their dispersion
ability is of key importance. A straightforward procedure for the covalent modification of
both single-walled and multi-walled CNTs with polymer grafts is presented. Self-initiated
photografting photopolymerization of vinyl monomers (styrene and 4-vinylpyridine) onto
CNTs results in a highly functionalized material with up to 44 wt.% of polymer grafts.
Using small-angle scattering, the effect of the modification of CNTs on their agglomeration
behavior in dilute toluene dispersions was studied. While small-angle X-ray scattering
gives overall information, small-angle neutron scattering together with the use of deuterated
solvents offers the possibility to highlight the polymer shells or the CNTs. The structure of
the CNTs and their agglomerates were modeled as fractal aggregates of homogeneous or
core-shell cylinders for single- and multi-walled CNTs, respectively. This way, the
dispersibility of the CNTs as well as the thickness of the shell formed by the grafted
polymers in dependence on the time of polymerization was characterized. The presence of
the covalently bound polymer was found to significantly improve the dispersion ability of
the CNTs. Improved dispersibility of the polystyrene-modified CNTs was also observed in
a poly(styrene-b-isoprene) diblock copolymer matrix, and it was shown that anisotropic,
nanostructured block copolymer may serve as a 3D template for the directed self-assembly
of the modified CNTs.