PDMS–Fluorous Polyoxetane–PDMS Triblock Hybrid Elastomers: Tough and Transparent with Novel Bulk Morphologies
Bibliographic record
Abstract
PDMS-3F-1.1-PDMS and PDMS-3F-4.5-PDMS triblock hybrid elastomers are investigated, wherein (1) 3F-1.1 and 3F-4.5 are poly(3-methyl-3-trifluoroethoxymethyl)-1,3-propylene oxide with M n = 1.1 or 4.5 kDa, (2) segments are linked by urethane/urea forming reactions, and (3) the intermediate PDMS-3F-PDMS aminopropyl end segments are end-capped with isocyanatopropyltriethoxysilane. After condensation cure, PDMS-3F-PDMS triblock hybrids (A-1.1 and A-4.5) form robust elastomers. In a second set, bis(triethoxysilylethane), BTESE, was incorporated to probe effects of increased siliceous domain content (B-1.1, B-4.5). All compositions are optically transparent due to nearly identical refractive indexes for 3F and PDMS segments. TM-AFM images for A-4.5, A-1.1, and B-4.5 fracture surfaces reveal microscale bulk phase separation. The A-4.5 triblock hybrid shows a particularly interesting morphology comprised of 2–3 μm ovaloids (low modulus) surrounded by a higher modulus matrix. A model is proposed for this microscale morphology based on the relative rates of physical network formation (PN, H-bonding) and chemical network formation (CN, SiO 1.5 ) during coating deposition Despite low hard segment weight percents (2.6–3.5) the hybrid triblocks have moderate toughness with strain at break ranging from 260 to 492%. Triblock hybrid elastomer B-1.1 has the highest −SiO 1.5 wt % (mostly from BTESE) and lowest 3F wt % (3F-1.1). No sign of microscale phase separation is observed by TM-AFM imaging, and a separate T g for the 3F segment is not detected by DMA; these findings are ascribed to network constrained phase separation of that results in 3F being incorporated in an “interphase”. The absence of a separate T g for 3F leads to a gradual decrease in storage modulus (8 to 1.4 MPa) from −90 to 150 °C. In contrast to the complex bulk morphology, TM-AFM imaging shows the hybrid surfaces are devoid of microstructural features attributable to phase separation. Based on contact angle measurements and XPS analysis, the outermost surface for all PDMS-3F-PDMS hybrid triblocks elastomers is dominated by PDMS.
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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 | 0.000 |
| 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".