New Phase Segregated Block Copolymers

Block copolymers are macromolecules composed of sequences, or blocks of chemically distinct repeat units. If the blocks within a block copolymer are nonmiscible phase segregation occurs. This behavior leads to microstructure formation in the nanometer range and leads to the formation of highly ordered structures within a bulk material. Thermoplastic elastomers are polymers which consist of such nonmiscible triblock copolymers leading to elastomeric behavior at room temperature but processability at higher temperatures. Due to the thermal instability the maximum usage temperature of these materials is restricted to a maximum of 150 C. The present project deals with the synthesis of new thermostable thermoplasic elastomers. Polyaryletherketones (PEEK), polyarylethersulfanes (PES) and polyisobutylene (PIB) will be combined in block copolymers using two different approaches : one via direct chemical linkage of functionalized oligomers, the other via hydrogen bond assiciation. of telechelics with hydrogen bond forming end group moieties. The living polymerisation of isobutylene mediated by titanium catalysts will enable the specific tailoring and functionalization of polyisobutylene macromonomers. Polycondensation methods with specific end stoppers will yield the corresponding functional PEEK/PES macromonomers. The combination of both types of functional polymers (PEEK/PES and PIB) will be achieved via chemical linkage of reactive functionalities and assiciation via hydrogen bonds. The strong interaction between the PEEK/PES segments on one hand and the PIB segments on the other hand will provide the driving force of the phase separation process and impart additional stability to the hydrogen bonded network. In addition a detailed investigation of the phase segregation process mainly via solid state NMR spectroscopy is planned. In particular spin diffusion methods and high resolution proton spectroscopy will yield detailed information on the phase structure as well as on the chemical composition. This will be related to the mechanical and chemical properties of these polymers and allow for a specific tailoring of the polymer and their microphase structure.

The funded project was located in the area of material science and technology, dealing with the development of new polymeric nanostructured materials and the investigation of their properties in bulk and thin films. The critical issue was to determine the final polymeric structure starting from the initial stage, the individual molecule. This resulted in the synthesis of macromolecules with specific size, shape and - most of all - intermolecular interaction, resulting in so called thermoplastic elastomers and nanocomposites. To this purpose, also specific nanometer-sized particles mediating conductive, semiconductive and luminescent properties were incorporated in these materials by use of specific molecular interactions. The resulting materials show an high degree of reversibility, due to the noncovalent nature of the interaction, leading to materials with exciting properties. Materials were investigated either as bulk-structure, or - alternatively - processed into thin films. Due to the reversible character new modulative materials with potential application in the field of microelectronics and high performance polymers are envisioned.