Aggregation‐Dependent Polymer Photochromism <i>via</i> Double Intramolecular Hydrogen Bonds from Excited State Intramolecular Proton Transfer
Bibliographic record
Abstract
Comprehensive Summary Excited‐state intramolecular proton transfer (ESIPT) involves photochemical tautomerization between two excited states (E* and K*) via intramolecular proton transfer. Developing polymer photochromism based on the photochemical tautomerization of organic ESIPT molecules has been rarely reported. We report the ESIPT molecule HBT‐2OH exhibits concentration‐dependent photochromic behavior in a polyurethane (PU) network. At low concentrations, HBT‐2OH primarily exists in the trans ‐enol configuration without intramolecular OH···N hydrogen bonds in PU, emitting blue fluorescence at ~464 nm (enol emission). Upon UV irradiation, the dihedral angle between the proton donor and acceptor twists to form an intramolecular OH···N H‐bond, converting trans ‐enol to cis ‐enol and resulting in ESIPT with pale yellow fluorescence at ~603 nm (keto emission). The photochromic effect of HBT‐2OH@PU diminishes at high concentrations due to that aggregation favors the cis ‐enol form. Control molecules HBT, HBO‐2OH , and HBI‐2OH show no photochromism in PU, confirming that ethanolyl branches and intramolecular OH···S hydrogen bonds stabilize the trans ‐enol configuration of HBT‐2OH . Incorporating these molecules into PMMA and PCL networks demonstrates that increased free volume and smaller aggregates enhance photochromism by reducing resistance to dihedral angle twisting. Density functional theory (DFT) calculations further confirm stable intramolecular heteroatomic hydrogen bonds (OH···S) exist in HBT‐2OH . This study offers new theoretical insights and opens avenues for research on polymer based photochromic materials.
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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".