Logo JG-Universität MainzProf. Dr. Axel Müller


PhD Thesis

Darstellung und Charakterisierung von hyper- und hochverzweigten Methacrylaten durch Gruppenübertragungspolymerisation

Peter Simon (01/2000-01/2000)

Johannes-Gutenberg-Universität Mainz


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 tert–butyl 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 13C–NMR 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 Mark–Houwink 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).

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