Photoinduced molecular reorientation dynamics in confined domains of Langmuir monolayers

2005 ◽  
Vol 122 (24) ◽  
pp. 244722 ◽  
Author(s):  
Joaquim Crusats ◽  
Rosa Albalat ◽  
Josep Claret ◽  
Jordi Ignés-Mullol ◽  
Ramon Reigada ◽  
...  
Keyword(s):  
Langmuir Monolayers ◽  
Molecular Reorientation ◽  
Reorientation Dynamics ◽  
Confined Domains

scholarly journals Incorporation of Molecular Reorientation into Modeling Surface Pressure-Area Isotherms of Langmuir Monolayers

Molecules ◽  
2021 ◽  
Vol 26 (14) ◽  
pp. 4372
Author(s):  
José Agudelo ◽  
Guilherme Volpe Bossa ◽  
Sylvio May
Keyword(s):  
Surface Pressure ◽  
Lateral Pressure ◽  
Langmuir Monolayers ◽  
High Energy ◽  
Cross Sectional Area ◽  
Inorganic Nanoparticles ◽  
Sectional Area ◽  
Molecular Reorientation ◽  
Cross Sectional ◽  
Pressure Area

Langmuir monolayers can be assembled from molecules that change from a low-energy orientation occupying a large cross-sectional area to a high-energy orientation of small cross-sectional area as the lateral pressure grows. Examples include cyclosporin A, amphotericin B, nystatin, certain alpha-helical peptides, cholesterol oxydation products, dumbbell-shaped amphiphiles, organic–inorganic nanoparticles and hybrid molecular films. The transition between the two orientations leads to a shoulder in the surface pressure-area isotherm. We propose a theoretical model that describes the shoulder and can be used to extract the energy cost per molecule for the reorientation. Our two-state model is based on a lattice–sublattice approximation that hosts the two orientations and a corresponding free energy expression which we minimize with respect to the orientational distribution. Inter-molecular interactions other than steric repulsion are ignored. We provide an analysis of the model, including an analytic solution for one specific lateral pressure near a point of inflection in the surface pressure-area isotherm, and an approximate solution for the entire range of the lateral pressures. We also use our model to estimate energy costs associated with orientational transitions from previously reported experimental surface pressure-area isotherms.

scholarly journals A multi-property fluorescent probe for the investigation of polymer dynamics near the glass transition

2014 ◽  
Vol 12 (9) ◽  
pp. 937-952 ◽  
Author(s):  
Joanna Siekierzycka ◽  
Catharina Hippius ◽  
Frank Würthner ◽  
René Williams ◽  
Albert Brouwer
Keyword(s):  
Electron Transfer ◽  
Glass Transition ◽  
Single Molecule ◽  
Molecular Reorientation ◽  
Electron Transfer Process ◽  
Perylene Bisimide ◽  
Quenching Process ◽  
The Matrix ◽  
Different Temperatures ◽  
Reorientation Dynamics

AbstractIn addition to the commonly observed single molecule fluorescence intensity fluctuations due to molecular reorientation dynamics, a perylene bisimide-calixarene compound (1) shows additional on-off fluctuations due to its ability to undergo intramolecular excited state electron transfer (PET). This quenching process is turned on rather sharply when a film of poly(vinylacetate) containing 1 is heated above its glass transition temperature (T g), which indicates that the electron transfer process depends on the availability of sufficient free volume. Spatial heterogeneities cause different individual molecules to reach the electron transfer regime at different temperatures, but these heterogeneities also fluctuate in time: in the matrix above T g molecules that are mostly nonfluorescent due to PET can become fluorescent again on timescales of seconds to minutes.The two different mechanisms for intensity fluctuation, rotation and PET, thus far only observed in compound 1, make it a unique probe for the dynamics of supercooled liquids.

scholarly journals Water in Mesoporous Confinement: Glass-To-Liquid Transition or Freezing of Molecular Reorientation Dynamics?

Molecules ◽  
2019 ◽  
Vol 24 (19) ◽  
pp. 3563
Author(s):  
Schranz ◽  
Soprunyuk
Keyword(s):  
Porous Silica ◽  
Mechanical Analysis ◽  
Mechanical Relaxation ◽  
Molecular Reorientation ◽  
Work Related ◽  
The Core ◽  
Liquid Transition ◽  
Relaxation Measurements ◽  
Reorientation Dynamics ◽  
Lower Temperature

The first mechanical relaxation measurements (f = 400 Hz) of water confined in micro-porous silica were performed more than 40 years ago. The authors reported a so called “capillary transition” (here denoted as P3) of water in the core of the pores and a second one at a lower temperature, which they called the “adsorbate transition” (P1 in present work) related to water near the surface of the pores. The capillary transition was identified with the freezing of water in the centre of the pores. However, even 40 years later, the origin of the adsorbate transition is not yet clear. One study relates it to the liquid-to-glass transition of the supercooled water in the pores, and another study to the freezing of the proton reorientations at the lattice defects. The present work shows the data from extensive dynamic mechanical analysis (DMA) measurements (f = 0.1 Hz–70 Hz) of water confined in mesoporous silica (d = 2.5, 5 and 10 nm), which are in favour of a liquid-to-glass scenario.

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