PhD Thesis
Darstellung und Charakterisierung von hyper- und hochverzweigten Methacrylaten durch Gruppenübertragungspolymerisation
Peter Simon (01/2000-01/2000)
Johannes-Gutenberg-Universität Mainz
Summary
The
Self-Condensing Group Transfer polymerization of
2-[(2-methyl-1-triethylsiloxy-1-propenenyl)oxy]ethyl
methacrylate (MTSHEMA) and the copolymerization with methyl
methacrylate (MMA)
and tertbutyl methacrylate (tBMA)
were investigated. Because MTSHEMA
consists of a polymerizable methacryolyl group and an initiating
silylketenactetal unit Self-Condensing Vinyl-Polymerization (SCVP)
leads to
hyperbranched methacrylates whereas the Self-Condensing Vinyl
Copolymerization
yields highly branched methacrylates, respectively.
The
homopolymerization of MTSHEMA at room temperature catalyzed by
tetrabutyl
ammonium bibenzoate generates only low molecular weight polymer.
Qualitative 13CNMR
spectroscopy shows, that this finding is due to a nucloephilic attack
of an
active chain end to a penultimate carbonyl group (backbiting reaction).
Furthermore, the reaction of an active chain end with the double bond
of the
core unit could be proven by kinetic evidence. The two side reactions
can be
suppressed by lowering the temperature and by the use of initiators.
Contrary
to the results of the homopolymerization, copolmerization of MTSHEMA
with
methyl methacrylate proceeds at room temperature without side
reactions. The
variation of the comonomer ratio provides control over the molecular
weight,
the degree of branching, and the viscosity in solution.
The
molecular weight distribution of all polymers was determined using size
exclusion chromatography with an on-line viscosity detector and an
on-line
multi-angle laser light scattering. Furthermore, this multi-detector
approach
enables the determination of the MarkHouwink parameters and the
corresponding
light-scattering exponent. For all polymers the Mark-Houwink exponents
of the
branched polymers are lower than those of the linear ones. This shows
that the
branched polymers exhibit a more compact structure in solution. The
comparison
of the contraction factors as determined from the viscosities and the
radii of
gyration permits an estimation of the degree of branching.
The
results of the homopolymerization as well as the copolymerization are
in
agreement with theory in first approximation. Deviation are due to the
complexity of the theoretical model.
The
results of viscoelatic spectroscopy show that the behavior of branched
polymers
in melt is in agreement with the Rouse theory indicating the absence of
entanglements.
Copolymerization
of MTSHEMA with tert-butyl
methacrylate yields highly branched poly (tert-butyl
methacrylate). Hydrolysis of this polymer leads to a highly branched
polyelektrolyte, poly(methacrylic acid).