Molecular Origin of the Odd–Even Effect of Macroscopic Properties of <i>n</i>-Alkanethiolate Self-Assembled Monolayers: Bulk or Interface?
Bibliographic record
Abstract
Elucidating the influence of the monolayer interface versus bulk on the macroscopic properties (e.g., surface hydrophobicity, charge transport, and electron transfer) of organic self-assembled monolayers (SAMs) chemically anchored to metal surfaces is a challenge. This article reports the characterization of prototypical SAMs of n-alkanethiolates on gold (CH3(CH2)nSAu, n = 6–19) at the macroscopic scale by electrochemical impedance spectroscopy and contact angle goniometry, and at the molecular level, by infrared reflection absorption spectroscopy. The SAM capacitance, dielectric constant, and surface hydrophobicity exhibit dependencies on both the length (n) and parity (nodd or neven) of the polymethylene chain. The peak positions of the CH2 stretching modes indicate a progressive increase in the chain conformational order with increasing n between n = 6 and 16. SAMs of nodd have a greater degree of structural gauche defects than SAMs of neven. The peak intensities and positions of the CH3 stretching modes are chain length independent but show an odd–even alternation of the spatial orientation of the terminal CH3. The correlations between the different data trends establish that the chain length dependencies of the dielectric constant and surface hydrophobicity originate from changes in the polymethylene chain conformation (bulk), while the odd–even variation arises primarily from a difference in the chemical composition of the interface related to the terminal group orientation. These findings provide new physical insights into the structure–property relation of SAMs for the design of ultrathin film dielectrics as well as the understanding of stereostructural effects on the electrical characteristics of tunnel junctions.
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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) | 0.001 | 0.001 |
| 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".