Effect of Group-14 and Group-16 Substitution on the Photophysics of Structurally Related Donor–Acceptor Polymers
Bibliographic record
Abstract
A series of eight polymers based on the parent structure, poly[2,6-(4,4-bis-(2-ethylhexyl)-4 H -cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT), were synthesized for a systematic group-14 and group-16 single atom substitution study. The eight polymers were constructed with C/Si/Ge and S/Se/Te varied in the donor and acceptor, respectively. By examining experimental spectroscopic data and DFT calculated geometry and electronic structure, we gain new physical insights into the effects of heavy atom substitution at different positions in a donor–acceptor polymer. Absorption and emission experiments demonstrate that group-14 substitution in the donor unit only slightly blue shifts the long wavelength absorption (HOMO to LUMO transition) and that group-16 substitution in the acceptor affects this absorption to a much greater extent. Solvatochromism experiments show that the charge transfer excited state is most polarized when the acceptor contains a lighter atom and is influenced very little by the atom in the donor. Changing the atom in the acceptor has less effect on the absorption of the Si-donor and Ge-donor polymers than the C-donor polymers. Polymers that contain C-donors are stronger light absorbers than their Si-donor and Ge-donor analogues regardless of which atom is in the acceptor position. These results clarify the effects of single atom substitution on donor–acceptor polymers and aid in the future design of polymers containing heavy atoms.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".