Temperature-driven phase transitions in oligo(ethylene glycol)-terminated self-assembled monolayers
2000 (English)In: JOURNAL OF PHYSICAL CHEMISTRY B, ISSN 1089-5647, Vol. 104, no 32, 7565-7569 p.Other (Other academic)
This letter explores the phase behavior of oligo(ethylene glycol) self-assembled monolayers using temperature-programmed infrared reflection absorption spectroscopy. The monolayers are formed by self-assembly of hexa(ethylene glycol) (EG(6)) and tetra(ethylene glycol) (EG(4))-terminated and amide group containing alkanethiols on polycrystalline gold. The ethylene glycol portions of the two monolayers are known to exist in two different conformations at room temperature: EG(6) in helical and EG(4) in all-trans (zigzag). The helical phase of the EG(6) gradually diminishes upon increasing the temperature and a pronounced conformational transition occurs around 60 degrees C, leading to a rapidly increasing population of all-trans conformers along the EG(6) chain. The EG(4) SAM exhibits a much simpler phase behavior. The oligomer conformation is marginally affected upon increasing the temperature to 75 degrees C, displaying the dominating all-trans phase, which possibly coexists with a small fraction of gauche-rich (disordered) regions. The reported conformational changes are reversible upon returning to 20 degrees C after stepwise heating to 70 degrees C.
Place, publisher, year, edition, pages
2000. Vol. 104, no 32, 7565-7569 p.
Engineering and Technology
IdentifiersURN: urn:nbn:se:liu:diva-49622OAI: oai:DiVA.org:liu-49622DiVA: diva2:270518