Reversible addition fragmentation chain transfer (RAFT) mediated polymerization of N-vinylpyrrolidone
Date
2008-03
Authors
Pound, Gwenaelle
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : University of Stellenbosch
Abstract
Xanthate-mediated polymerization was investigated as a tool for the preparation
of well-defined poly(N-vinylpyrrolidone) and copolymers of N-vinylpyrrolidone. Some
results regarding the monomer vinyl acetate are included, mostly for comparison
purposes. The structure of the leaving/reinitiating group of the xanthate mediating agent
was tuned to match the monomer reactivity. This was achieved by studying the
initialization behaviour of monomer-xanthate systems via in situ 1H-NMR spectroscopy.
Additionally, the latter technique was valuable to identify side reactions affecting the
monomer, xanthate and/or polymeric species. Subsequently, experimental conditions
were defined, and used to optimize the level of control achieved during polymerization.
Block copolymers were prepared from a xanthate end-functional poly(ethylene
glycol) with both vinyl acetate and N-vinylpyrrolidone. Finally, the preparation of
poly(N-vinylpyrrolidone) with a range of well-defined end groups was achieved via postpolymerization
treatment of the xanthate end-functional polymerization product. 3
different routes were investigated, which lead to poly(N-vinylpyrrolidone) with 1)
aldehyde or alcohol, 2) thiol or 3) unsaturated ω-chain-end functionality, in high yield,
while the α-chain-end functionality is defined by the structure of the xanthate leaving
group. The ω-aldehyde end-functional poly(N-vinylpyrrolidone) was successfully
conjugated to the lysine residues of the model protein lysozyme via reductive amination.
Particular attention was drawn to characterizing the polymerization products.
NMR spectroscopy, liquid chromatographic and mass-spectroscopic techniques were
used. The major achievements emerging from polymer analysis carried out in this study
included the following:
- a library of NMR chemical shifts for N-vinylpyrrolidone derivatives;
- an estimation of the critical conditions for poly(N-vinylpyrrolidone) relevant for
separation according to the polymer chain-ends;
- conditions for the separation of block-copolymers comprising a poly(ethylene
glycol) segment and a poly(N-vinylpyrrolidone) or poly(vinyl acetate) segment
via liquid chromatography; - valuable results on matrix-assisted laser ionization-desorption time-of-flight mass
spectroscopy (MALDI-ToF-MS) of poly(N-vinylpyrrolidone).
Description
Thesis (PhD (Chemistry and Polymer Science)--University of Stellenbosch, 2008.
Keywords
Living polymerization, N-vinylpyrrolidone, Raft, Xanthtate, Dissertations -- Polymer science, Theses -- Polymer science, Vinyl polymers, Addition polymerization