Tapered Multiblock Star Copolymers: Synthesis, Selective Hydrogenation, and Properties
| Autor: | George Floudas, Philipp von Tiedemann, Ramona D. Barent, Jiaqi Yan, Richard A. Register, Holger Frey, Richard J. Spontak |
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| Rok vydání: | 2020 |
| Předmět: |
Toughness
Materials science Polymers and Plastics Precipitation (chemistry) Organic Chemistry Analytical chemistry 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology Elastomer 01 natural sciences 0104 chemical sciences Styrene Inorganic Chemistry chemistry.chemical_compound chemistry Ultimate tensile strength Materials Chemistry Copolymer Polystyrene Elongation 0210 nano-technology |
| Zdroj: | Macromolecules. 53:4422-4434 |
| ISSN: | 1520-5835 0024-9297 |
| Popis: | Two series of well-defined multiblock four-arm tapered star copolymers with “arms” of the type poly(styrene)-block-poly(isoprene-grad-styrene), (SI/S)₄, were synthesized on a multigram scale with short reaction times. Targeted molecular weight (M) values ranged from 80 to 240 kg mol–¹ with polystyrene (PS) compositions of 40 and 60 wt %. Narrowly distributed (Đ = 1.04–1.12) copolymers were obtained regardless of M and without additional purification beyond precipitation. At sufficiently high M, members of the 40 wt % PS series possessed either a cylindrical or bicontinuous morphology, whereas the 60 wt % PS series yielded lamellae. The star copolymers outperformed their corresponding linear analogues with respect to ultimate toughness and elongation at break. Young’s moduli of up to 304 ± 11 MPa were reached, and the overall toughest (83 ± 2 MJ/m³) star copolymer exhibited the highest strain at break (1198 ± 34%). Catalytic hydrogenation of the PI segments was achieved selectively without saturation of styrene units at conversions of ≥98%. More pronounced strain hardening occurred upon hydrogenation. Modulus, toughness, and ultimate strength of the linear tapered copolymer increased substantially upon hydrogenation to poly(styrene)-block-poly((ethylene-alt-propylene)-grad-styrene), SEP/S. However, these mechanical properties for the star copolymer were found to decrease upon hydrogenation to (SEP/S)₄. These materials, particularly the unsaturated multiblock stars of the highest M, are promising candidates for future advanced materials that require extremely tough elastomers. |
| Databáze: | OpenAIRE |
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