Effect of Topology and Molecular Properties on the Rheology and Fatigue Behavior of Solid Polystyrene/Polyisoprene Di- and Triblock Copolymers
Bibliographic record
Abstract
The effect of molecular properties on the rheological and fatigue behaviors of solid polystyrene (PS)/polyisoprene (PI) block copolymers was investigated. Linear model systems of PS–PI (SI), PS–PI–PS (SIS), and PI–PS–PI (ISI) block copolymers were synthesized via anionic polymerization with well-defined molecular structure variation such as block order, PI content, molecular weight, microstructure, and polydispersity. The different block sequences (SI vs SIS vs ISI) result, for similar PI contents, in different microdomain sizes, which correlate with the phase-separated morphologies as quantified via small-angle X-ray scattering (SAXS). The samples were mechanically characterized in the solid state via strain sweep tests to obtain their storage G ′(γ 0 ) and loss G ″(γ 0 ) moduli at room temperature as well as their nonlinear properties determined via the Fourier transform (FT) of the stress response. The fatigue behavior was determined via strain-controlled oscillatory torsion tests. First, the effect of strain amplitude on the number of cycles to failure was analyzed via Wöhler curves, specifically strain amplitude vs fatigue lifetime. A significant effect of the block sequence order, the microdomain size, and the chain dynamics on fatigue resistance was found. The fatigue resistance of SI diblock with 30 mol % PI outperforms the SIS or ISI triblock copolymer with a similar composition and, compared to neat PS, increases by a factor of 10 and even 4500, respectively. Second, the time-dependent stress response was analyzed via Fourier transform rheology to better quantify the time-dependent behavior of the nonlinear mechanical parameters and to determine quantitative parameters related to failure onset. Since the fatigue tests were performed under large amplitude oscillatory shear (LAOS), higher harmonics were detected and the time evolution was quantified in the FT spectra. Linear parameters such as the storage ( G ′) and loss ( G ″) moduli, as well as the third ( I 3 ) harmonic over the fundamental one ( I 1 ), were analyzed, leading to clear indications related to both brittle or ductile failure mechanisms.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".