Logo JG-Universität MainzProf. Dr. Axel Müller


PhD Thesis

Polarmodifikation von Butadienkautschuk mit Polyethylenglykol

Mabel Braun (01/2002-01/2002)


The synthesis of polar modified polybutadiene rubbers by reaction of living anions of polybutadiene with chain-end functionalised polyethylene glycol (PEG) was investigated. The reaction system and the strategy of copolymer synthesis were determined by the copolymer’s potential use. Polybutadienes (PB) should have a high fraction of 1,4-units to serve as adhesion-increasing components in silica-filled rubber mixtures for tire applications. On the other hand, modification reactions with functionalised PEG should be uncomplicated and cheap.

Two types of functionalised PEG were generated. First, PEG with a substitutable end group were reacted with living anions of polybutadiene. Those PEG were carrying chlorine or iodine atoms or sulfonic acid ester end groups. The latter were not suitable for replacement by PB anions under chosen conditions. Using halide-functionalised PEG, chain coupling efficiencies of up to 50 % of the theoretical value were reached. Side products were identified by liquid chromatography under critical conditions (LACCC) and two-dimensional chromatography (LACCC coupled with gel permeation chromatography). This reaction is uncomplicated in realisation and hence provides potential of industrial use - but it is not complete due to its reaction mechanism.

An alternative way is to couple living PB-anions with PEG carrying a non homopolymerisable double bond, e. g. polyethylene glycols with a diphenyl ethylene (DPE) or benzophenone end group. Numerous side products were found in the reaction of PEG-DPE with the anions, as was modification of PB with a benzophenone-functionalised PEG. The latter led to copolymers with PEG fractions of 67 % of the theoretical value. Formation of side products was again clarified by two-dimensional chromatography. By changing some parameters, better control of this type of reaction could be achieved. Thus it may be an interesting method in synthesis of block copolymers or branched polymers from dienes and polyethylene glycol.

Within the framework of an industry cooperation several modified polybutadienes were synthesised in lots of 500 g, using chlorine-functionalised PEG. The copolymers were utilised in typical rubber mixes for tire applications by the cooperation partner. Mechanical properties of the uncured mixes and of cured specimens were specified by typical methods. As a result of the very small polyethylene glycol proportion within the mixture no distinct influence of this fraction on the determined properties could be detected

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