Synthesis and Property Optimization of Ordered, Aryl Dense Polysiloxanes Using Boron Catalysis
Bibliographic record
Abstract
Silicones are widely used polymeric materials due to their unique properties. The material properties of silicones may be altered by incorporating various organic groups. Traditional methods for linear silicone synthesis involve ring-opening polymerization, which leaves the growing chain susceptible to acid or base mediated chain redistribution and the formation of cyclic monomer byproducts. The Piers-Rubinsztajn (PR) reaction is an alternative siloxane synthetic route that avoids the use of tin- or platinum- based, or of Brønsted acid/base catalysts. Siloxane bond formation is catalyzed by tris(pentafluorophenyl)borane (B(C6F5)3) (R’3Si-H + RO-SiR”3 → R’3Si-O-SiR”3 + RH); alkoxysilanes can be replaced with silanols or alkoxybenzenes. The catalytic activity of B(C6F5)3 was shown to be hindered by trace water in solution; water acts as a Lewis base coordinating to B(C6F5)3. Since the hydrate-free form of B(C6F5)3 is required to initiate a PR reaction, water can act as an inhibitor. In a somewhat contradictory fashion, water was also shown to react with hydrosilanes via a B(C6F5)3 catalyzed hydrolysis reaction to give silanols, that themselves are reagents for the process. The reactivity of alkoxysilanes (or aryl ethers) in the PR reaction was found to be much quicker than water. This was exploited in the synthesis of Ax(AB)yAx triblock copolymers. The aryl rich AB core was first synthesized using the PR reaction. Excess silicone condensed via hydrolysis forming the A blocks. This method of exploiting relative reactivity to tune structure was applied to elastomers made using a single linker (eugenol) with multiple functional groups – elastomer morphology was controlled by changing order of addition. The development of aryl dense silicones is of interest for use in electronic devices. Phenylmethyl homopolymers and highly ordered phenyl pendant copolymers (Ph/Si ratio of 0.5-1.5) were synthesized from monomers to give polymers with high refractive indices (1.51-1.59) and Mw up to 170 kDa. Statistically relevant libraries of aryl functional silicones were developed using combinatorial chemistry in order to analyze their structure-property relationship. Incorporating aromatic groups into silicones worked to elevate thermal stability, refractive index and improve the mechanical strength of silicone rubbers.
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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) | 0.001 | 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 | 0.001 |
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".