Zur anionischen Copolymerisation von 5-( N,N-Dialkylamino)isoprenen
Gerd Mannebach (01/1999-01/1999)
The incorporation of amine functions into diene monomers leads to polar monomers which provide access to new polymers with a wide range of properties. Within this work homo- and copolymers of 5-(N,N-dialkylamino)isoprenes were prepared in n-hexane and THF. It is shown that side reactions occur in nonpolar solvents at elevated temperatures, which prevent full conversion. A polymerization in THF - initiated with alkyllithium - is extremely slow. In contrast to nonpolar solvents it shows first order kinetics with respect to the concentration of monomers. In the copolymerization of 5-(N,N-dialkylamino)isoprenes in n-hexane the composition of the copolymers is strongly dependent on the steric effects of the alkyl side chains of the amino group. For larger differences in the bulkiness of the alkyl side chains the structures are more blocklike. During the copolymerization of 5-(N,N-dialkylamino)isoprene with 1,3-butadiene one finds that the polar aminoisoprene is incorporated first into the polymer. On varying the dialkylaminogroup, copolymers with tapered or blocklike structures are obtained which contain different 1,2-contents of butadiene. Kinetic experiments show that the solubility of the living polymer and the rate of propagation are dependent on intra- and intermolecular interactions between the amino functions and the living chain ends. The reactivity ratios in the copolymerization with 1,3-butadiene were determined. Rheological experiments indicate an interaction of the dialkylamino groups in the polymer melt as well as microphase separation. Polar modified solution SBRs were synthesized by anionic terpolymerization of 5-(N,N-dialkylamino)isoprenes with styrene and 1,3-butadiene in n-hexane, with an addition of small amounts of THF. By comparing the kinetic experiments in the absence and presence of THF an increase of the rate of propagation is found for the statistical copolymerization of styrene with 1,3-butadiene. In a cooperation with BAYER AG these new polarmodified solution SBRs were investigated in rubber mixtures and an enhancement of properties compared to conventional polymers used for profile tires was found.