Polybutadien und Butadien enthaltende Copolymere mit gezielt eingebauten vulkanisierbaren Gruppen durch RAFT-Polymerisation

Abstract

Reversible Addition Fragmentation Chain Transfer (RAFT) polymerisation is a radical polymerisation based on the principle of degenerative chain transfer. Polymers produced by this method feature a narrow polydispersity and can form complex macromolecular architectures. Furthermore, functionalisation of polymer chains is easily achieved via RAFT polymerisation since ideally every single polymer chain carries a RAFT unit which can then be modified further, in a defined way. This thesis focuses on the functionalisation of polybutadiene and 1,3-butadiene-containing copolymers with specifically built-in sulphur-containing groups by using RAFT-agents in different ways. Two approaches were pursued: α,ω-functionalisation of polymer chains using modified RAFT agents and functionalisation along the polymer chains by specific monomers. Due to the intended industrial application of the polymers, easily scalable syntheses had priority during this project. As the RAFT unit already consists of a sulphur-containing group, strategies for functionalising the RAFT leaving group were developed and investigated to enable the formation of an α,ω-functionalised polymer. In addition to common RAFT agents, macro RAFT agents were used. In this case the sulphur-containing groups were tethered to the polymer in situ during the polymerisation process. Furthermore, the synthesis of styrene-based monomers was successful. Due to the similarity of styrene and 1,3-butadiene, the styrene derivatives copolymerise well with 1,3-butadiene and incorporate the sulphur-containing group along the polymer chain. Further investigations focused on the copolymerisation behaviour of these monomers. Extensive studies with styrene as model system for 1,3-butadiene were conducted. The obtained results were verified in copolymerisation reactions of the functionalized monomers with 1,3-butadiene. Moreover, it was possible to prove the applicability of switchable RAFT agents for the synthesis of poly(butadiene)-block-poly(vinyl acetate), even though 1,3-butadiene and vinyl acetate are two monomers which differ in their electronic behaviour and do not form copolymers in a conventional radical polymerisation. Because of the similarity of vinyl acetate and ethylene, these findings open up new possibilities in the synthesis of poly(butadiene)-block-poly(ethylene) using degenerative chain transfer polymerisations. Therefore, the array of non-polar monomers suitable for the synthesis of block copolymers via RAFT polymerisation is extended considerably.