Novel heat-resistant materials: Synthesis and properties of fully saturated hydrocarbon-based block copolymers.

摘要

Polystyrene (PS)-based materials are widely used in many applications. However, the upper use temperatures of these materials are limited by the T_g of PS. This thesis demonstrated that novel PCEP-based materials can be used as high upper use temperature substitutes without sacrificing the properties and manufacture cost.; High T_g materials were prepared using a two-step process: anionic copolymerization of α-methylstyrene (αMS) with styrene (leading to copolymers referred to as SAMS), with subsequent catalytic hydrogenation. The product, poly(cyclohexyl ethylene-co-2-cyclohexyl propylene) is referred to as PCEP. PCEP exhibits T_g values between 140°C and 178°C, depending on the composition and composition distribution in the polymerization product. Other properties of PCEP such as thermal stability, density, modulus and rheological properties were also examined and compared to those of PS.; We also successfully incorporated PCEP copolymers into multiblock (di-, tri-, penta-) copolymers with poly(ethylene-co-ethyl ethylene) (PEE). The properties of the block copolymer are influenced by the mole percent of 2-cyclohexyl propylene units in the PCEP block (CP%) and the mole percent of hydrogenated 1,2-polybutadiene units in the PEE block (1,2%). Increasing CP% increases the upper T_g without affecting the χ between the two blocks, the lower T_g, the rheological behavior and the tensile properties of the block copolymers. Varying 1,2%, on the other hand, can significantly change χ, the T_g's, as well as the flow and tensile properties.; This thesis also investigated the flow and tensile properties of elastomeric PCHE-PEE₆₀-PCHE triblock and matched PCHE-PEE₆₀-PCHE-PEE ₆₀-PCHE pentablock copolymers with twice the molecular weights. Pentablock copolymers exhibited similar tensile properties at room temperature as those of triblock copolymers. At elevated temperatures, pentablock copolymers are more difficult to relax under stress. This is likely due to required coordinated microdomain movements in a pentablock copolymer.