Polymorphism in Biphenyl-Based Self-Assembled Monolayers of Thiols

Abstract

Self-assembled monolayers of omega-(4'-methylbiphenyl-4-yl) butanethiol (H3C-C6H4-C6H4-(CH2)n-SH) on Au(111) substrates were investigated with scanning tunneling microscopy and contact angle measurements. A striking polymorphism was observed upon annealing, and structural changes were paralleled by a switch in stability against exchange by other thiols from unstable to stable. The phase formed at temperatures above 413 K was characterized by a very high structural perfection over areas exceeding 105 nm2. The results suggest an additional dimension in the control of structure and properties of thiol monolayers if different factors contributing to the energetics of SAMs enter in a competing rather than a cooperative way.

Odd‐Even Effects in Ion‐Beam‐Induced Desorption of Biphenyl‐Substituted Alkanethiol Self‐Assembled Monolayers

“…Importantly, this odd-even variation in the BPnS/Au(111) film structure is also reflected in different aspects of the film stability such as: 1) stability against exchange by other thiols, [16,17] 2) electrochemical stability, [18,19] 3) stability towards electron-induced modification, [20] and 4) stability towards thermally induced phase transitions. [21][22][23] In all these odd-even effects, related to the different aspects of the film stability, the odd numbered BPnS/Au(111) SAMs are more stable. A simple phenomenological model has been proposed [22] for explaining this difference in stability of odd-and even-numbered BPnS/Au(111) SAMs.…”

Systemische Chemie an Grenzflächen: Fernsteuerung von Oberflächeneigenschaften

“…[18,19] [20] durch die Adsorption der Moleküle aufgehoben wird oder ob diese relativ komplizierte Rekonstruktion des Substrats wie im Falle der Adsorption von Hexa-peri-hexabenzocoronen (planaren Graphitsegmenenten) bestehen bleibt. [12,13] Außerdem lässt die relativ hohe Unordnung, die aus den STM-Daten ersichtlich ist, darauf schließen, dass die laterale Ordnung der TATA + -Monoschichten deutlich geringer als in thiolatbasierten SAMs [21] ist. In zukünftigen Arbeiten gilt es zu klären, ob sich dieser Nachteil durch eine Optimierung der TATA + -Einheit beheben lässt.…”

Interfacial Systems Chemistry: Out of the Vacuum—Through the Liquid—Into the Cell

“…In these two-dimensional SAM monocrystals, the diameter of the defect-free areas may be 50 nm and more. [31] …”