Looking for the glass transition in a single molecular layer on the water surface

Cristofolini, Luigi; Cicuta, Pietro; Fontana, Marco

doi:10.1088/0953-8984/15/11/325

Cited by 6 publications

(3 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We first describe the properties of Langmuir monolayers of PANI both in its conducting and insulating forms, which are obtained by spreading the same amount of PANI either onto pure water, or onto an acidic subphase. This allows us to explore the phases of polyaniline in the most pure 2D form, in a very unconventional morphology, and free from the dead layer effects and substrate interactions which have always been a problem in analyzing the data for very thin films. − …”

Section: Resultsmentioning

confidence: 99%

Doping-Induced Conductivity Transitions in Molecular Layers of Polyaniline: Optical Studies of Electronic State Changes

et al. 2009

View full text Add to dashboard Cite

The doping-induced conductivity transitions in molecular layers of polyaniline have been studied by monitoring the correlated optical and spectroscopic changes using spectroscopic and single wavelength extinction ellipsometry, also in total internal reflection mode (TIRE), together with reflection spectrometry. The measurements were performed on deposited multilayers as well as on a Langmuir monolayer at the air-water interface, as a function of acidic doping. We found that the characteristic spectroscopic features of conducting and insulating polyaniline persisted down to the single layer, both in the solid state and at the air-water interface. We also investigated in real time the modulation of conductivity induced by the intercalation of Li ions in the polyaniline film, by a combination of time-resolved ellipsometry and reflectivity spectra measurements. In this case, the enhanced sensitivity provided by the TIRE geometry, combined with the relatively fast time scale accessible by the single wavelength ellipsometry, allowed us to follow in detail in real time the doping/dedoping process.

show abstract

Section: Resultsmentioning

confidence: 99%

Doping-Induced Conductivity Transitions in Molecular Layers of Polyaniline: Optical Studies of Electronic State Changes

et al. 2009

View full text Add to dashboard Cite

show abstract

“…Such experiments were motivated by the work of Cicuta and co-workers on poly (vinyl acetate) monolayers. 30,31 During the cycles, the monolayers were compressed at constant speed (25 mm min À1 ) up to a predefined value of the surface pressure, and then they were fully expanded again at the same rate. The cycles were repeated with an increased target value of the surface pressure and the layer recompressed and reexpanded.…”

Section: Compression-expansion Cycles Before the Collapse Of The Mono...mentioning

confidence: 99%

Viscoelasticity of semifluorinated alkanes at the air/water interface

et al. 2011

View full text Add to dashboard Cite

As semifluorinated alkanes (SFA) present an unusual class of mesogenic units for supramolecular structure formation, the study of their physical properties and self-assembly at fluid interfaces is of substantial relevance. To this end, the two-dimensional phase behavior and the viscoelastic properties of semifluorinated alkanes with symmetric number of carbon atoms in the fluorinated and hydrogenated side chains (F(CF 2 ) 12 -(CH 2 ) 12 H and F(CF 2 ) 11 CH 2 -core-(CH 2 ) 12 H with dibromophenyl core were investigated at the air/water interface and compared to the asymmetric F(CF 2 ) 12 (CH 2 ) 20 H system. Surface pressure/area isotherms and compression-expansion cycles were recorded at 20 C, 40 C, and 50 C. Depending on the molecular details, an unexpected phase transition and hysteresis in compression-expansion cycles could be observed. Interfacial rheology revealed for all monolayer systems a solid-like viscoelastic response over the investigated range of surface pressures. The interfacial storage modulus G 0 i and interfacial loss modulus G 00 i increased with increasing surface pressure. More importantly, at constant surface pressure the simple semifluorinated alkanes, forming nearly circular 2D micellar structures at the interface, exhibited rheological properties reminiscent of glass-like colloid systems. On the other hand, the SFA with the dibromophenyl core formed 2D interfacial micelles of highly elongated shape with dendritic domains and exhibited gel-like rheological properties, similar to those of the asymmetric alkane. Moreover, with increasing surface pressure the response of the asymmetric system alters from glassy to gel-like. These findings suggest that fine differences in the molecular structure are reflected in the linear viscoelastic response of the Langmuir films, and hence offer the possibility to molecularly tune the rheology of fluid interfaces.

show abstract

“…Yet, water might still interact favorably with the chains and act as a partial solvent. Then, their phase transitions like crystallization, [ 4 ] as well as other temperature dependent phenomena such as the glass transition, [ 5–7 ] are strongly affected. This is especially applicable for swellable networks and nanostructured materials, where water uptake is near instantaneous and can therefore affect the whole material, not just its surface.…”

Section: Introductionmentioning

confidence: 99%

Effect of Water on Crystallization and Melting of Telechelic Oligo(ε‐caprolactone)s in Ultrathin Films

Saretia

Machatschek

Bhuvanesh

et al. 2021

Adv Materials Inter

View full text Add to dashboard Cite

The thermal behavior of ultrathin, semi‐crystalline films of oligo(ε‐caprolactone)s (OCLs) with hydroxy or methacrylate end groups, is studied by the Langmuir technique in dependence on mean molecular areas and crystallization temperatures. The films on solid substrate as obtained by Langmuir–Schaefer transfer exhibit different lamellar thicknesses, crystal number densities, and lateral sizes. The melting temperature of OCL single crystals at the water and solid surface is proportional to the inverse crystal thickness and generally lower than in bulk PCL. An influence of OCL end groups on the melting behavior is observed mainly at the air–solid interface, where methacrylate end capped OCL melts at lower temperatures than hydroxy end capped OCL. Comparing the underlying substrate, melting/recrystallization of OCL ultrathin films is achievable at lower temperatures at the air–water interface than at the air–solid interface, where recrystallization is not identifiable. Recrystallization at the air–water interface generally occurs at higher temperature than the initial crystallization temperature. The surface pressure, as an additional thermodynamic variable, seems to further affect the crystallization behavior, with crystal thickness and lateral growth rate increasing with surface pressure. The results presented here are important when designing temperature‐sensitive or active nanostructured materials or interfaces based on OCL.

show abstract

Looking for the glass transition in a single molecular layer on the water surface

Cited by 6 publications

References 25 publications

Doping-Induced Conductivity Transitions in Molecular Layers of Polyaniline: Optical Studies of Electronic State Changes

Doping-Induced Conductivity Transitions in Molecular Layers of Polyaniline: Optical Studies of Electronic State Changes

Viscoelasticity of semifluorinated alkanes at the air/water interface

Effect of Water on Crystallization and Melting of Telechelic Oligo(ε‐caprolactone)s in Ultrathin Films

Contact Info

Product

Resources

About