Abstract
This work focuses on the synthesis of amphiphilic triblock terpolymers as promising can-didates for membrane applications via combination of anionic and reversible addition–fragmentation chain transfer (RAFT) polymerization. Two successful synthesis ap-proaches towards amphiphilic poly(styrene–block–isoprene–block–N,N-dimethylacryla-mide) (PS–b–PI–b–PDMA) triblock terpolymers were established. For both approaches, narrow-distributed OH-end-group functionalized poly(styrene–block–isoprene) (PS–b–PI–OH) diblock copolymers synthesized via anionic polymerization serve as basic mate-rial. These end-group functionalized diblock copolymers allow a linkage with carboxylic-acid containing agents via a Steglich-esterification to introduce the third block. Therefore, COOH-end-functionalized PDMA homopolymers synthesized by a RAFT polymeriza-tion with high control over the molecular weight were linked to the diblock copolymer allowing synthesis of low-molecular weight triblock terpolymers. As a second approach, carboxylic-acid functionalized RAFT agents were attached to the diblock copolymers forming macroRAFT agents which were subsequently chain extended to preserve PS–b–PI–b–PDMA triblock terpolymers. In addition to the desired triblock terpolymer, the products from both synthesis approaches contain unreacted initial materials as well. Fur-thermore, first essential steps towards the synthesis of amphiphilic poly(isoprene–block–styrene–block–4-vinylpyridine) (PI–b–PS–b–P4VP) triblock terpolymers are described.
The morphology of the products from the synthetic approaches for the synthesis of the PS–b–PI–b–PDMA triblock terpolymers was investigated. In bulk, a microphase-sepa-rated structure was discovered for the products from both synthetic approaches. The prod-uct after the Steglich-esterification of the diblock copolymer with the PDMA homopoly-mer shows a core-shell morphology in a polystyrene matrix, while in the product after the chain extension a core-shell-shell morphology in a PDMA matrix is observed. By tem-perature annealing and subsequent solvent vapor annealing, microphase-separated sur-face structures of spin-coated thin film with different domain sizes could be obtained.
