Although, the use of vinyl pyridine polymers, especially as matrices for
nanoparticle synthesis, is growing considerably, the knowledge of thermal
degradation behavior is still missing in the literature. In this study, thermal
degradation characteristics of the homopolymers / poly(4-vinylpyridine), P4VP,
and poly(2-vinylpyridine), P2VP, the diblock copolymers / polystyrene-blockpoly(
2-vinylpyridine), (PS-b-P2VP) and polystyrene-block-poly(4-vinylpyridine),
(PS-b-P4VP), and the metal functional vinyl polymers / cobalt-polystyrene-blockpoly(
2-vinylpyridine) and cobalt-polystyrene-block-poly(4-vinylpyridine) were
investigated by direct pyrolysis mass spectrometry. The effects of the position of
the nitrogen in the pyridine ring, composition and molecular weight of diblock
copolymer and coordination of the metal to the pyridine ring of the copolymer on
thermal behavior were also investigated. The results showed that unlike most of
the vinyl polymers that decompose via depolymerization, P2VP degrades
through opposing reaction pathways / depolymerization, proton transfer to N
atom in the pyridine ring yielding unsaturated linkages on the polymer backbone
that decompose slightly at higher temperatures and loss of pyridine units. On the
other hand the thermally less stable P4VP decomposition follows
v
depolymerization in accordance to general expectations. Another finding was the
independent decomposition of both components of the diblock polymers, (PS-b-
P2VP) and (PS-b-P4VP). Thermal degradation occurs in two main steps, the
thermally less stable P2VP or P4VP chains degrade in the first step and in the
second step decomposition of PS takes place.
It was also concluded that upon coordination of metal, thermal stability of both
P2VP and P4VP increases significantly. For metal functional diblock copolymers
thermal degradation of chains coordinated to Co metal through N in the pyridine
ring occurred in three steps / cleavage of pyridine coordinated to Co, coupling and
H-transfer reactions yielding unsaturated and/or crosslinked structure and
decomposition of these thermally more stable unsaturated and/or crosslinked
blocks. TEM imaging of the metal functional block copolymers along with the
results of the pyrolysis mass spectrometry pointed out that PS-b-P2VP polymer is
a better and more effective matrix for nanoparticle synthesis.
| Identifer | oai:union.ndltd.org:METU/oai:etd.lib.metu.edu.tr:http://etd.lib.metu.edu.tr/upload/12609892/index.pdf |
| Date | 01 September 2008 |
| Creators | Elmaci, Aysegul |
| Contributors | Hacaloglu, Jale |
| Publisher | METU |
| Source Sets | Middle East Technical Univ. |
| Language | English |
| Detected Language | English |
| Type | M.S. Thesis |
| Format | text/pdf |
| Rights | To liberate the content for public access |
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