Hysteresis of monolayers

Chen, Y. L., Helm, C. A., and Israelachvili, J. N. Molecular mechanisms associated w ith adhesion and contact angle hysteresis of monolayer surfaces. ]. Phys. Chem., 95, 10736 (1991). 

Chen YL, Helm CA, IsiaelachviUe JN (1991) Molecular mechanisms associated with adhesion and contact angle hysteresis of monolayer siutfaces. J Phys Chem 95 10736-10747... 

Yamada S and Israelachvili J N 1998 Friction and adhesion hysteresis of fluorocarbon surfactant monolayer-coated surfaces measured with the surface forces apparatus J. Rhys. Chem. B 102 234-44... 

Effect of phase state of monolayers of hexadecylsiloxane supported on oxidized PDMS-hysteresis in interfacial energetics as determined by contact mechanics and contact angles... 

Figure 8.12 (a) XMCD detected hysteresis of magnetization for the thick layer sample TL1 (above) and the monolayer sample ML1 (below) on HOPG measured at 7 K. The inset shows the enlargement of the central part of both hysteresis, (b) XAS spectra at the M45 edge of Tb for ML1 with helicities parallel (I11,... 

The states produced by compression of monolayers are not necessarily at thermodynamic equilibrium, but may be metastable. In some cases, this is manifested clearly by different force-area curves being produced at different rates of compression. Slow reorganization of monolayer molecules is also apparent as hysteresis when films are repeatedly compressed and expanded. In chiral monolayers, the rates of molecular reorganization may be stereospecific as well as the thermodynamic behavior. 

The adsorption isotherm of N, on FSM-16 at 77 K had an explicit hysteresis. As to the adsorption hysteresis of N-, on regular mesoporous silica, the dependencies of adsorption hysteresis on the pore width and adsorbate were observed the adsorption hysteresis can be observed for pores of w 4.0nm. The reason has been studied by several approaches [5-8]. The adsorption isotherm of acetonitrile on FSM-16 at 303K is shown in Fig. 1. The adsorption isotherm has a clear hysteresis the adsorption and desorption branches close at PIP, = 0.38. The presence of the adsorption hysteresis coincides with the anticipation of the classical capillary condensation theory for the cylindrical pores whose both ends are open. The value of the BET monolayer capacity, nm, for acetonitrile was 3.9 mmol g. By assuming the surface area from the nitrogen isotherm to be available for the adsorption of acetonitrile, the apparent molecular area, am, of adsorbed acetonitrile can be obtained from nm. The value of am for adsorbed acetonitrile (0.35 nnr) was quite different from the value (0.22 nm2) from the liquid density under the assumption of the close packing. Acetonitrile molecules on the mesopore surface are packed more loosely than the close packing. The later IR data will show that acetonitrile molecules are adsorbed on the surface hydroxyls in... 

Measurement of contact angles hysteresis. Transference of monolayers from water to solid surfaces. Multilayers... 

As an example, herein we explain the characterization of the combinatorial Libraries 1 and 2, mentioned above, which were synthesized using the solution-based procedure. Contact angle and ellipsometry data of the monolayer Libraries 1 and 2 are summarized in Fig. 4.1. Amino terminated SAMs formed from /V-13-(trimethoxysilyl)propyl]ethylenediamine (TPEDA) have an advancing contact angle (6j of 60°, and a hysteresis of 250.34 Hysteresis (0a - 6) values range from... 

A hard gelatin capsule exhibited moisture sorption depending on humidity, the hysteresis of which was analyzed by the Young-Nelson hypothesis. This allowed the formation of a monolayer of adsorbed moisture to be distinguished from normal condensation of moisture and from absorption of moisture (Fig. 185).72S... 

After verifying that the dried slide showed no contact angle hysteresis, clean glass slides were immersed in a suitable concentration of n-alkyldimethyl monochloro-silane in dried toluene and allowed to equilibrate for 15 min. Silanization reaction time was 30 min for the formation of monolayers at room temperature (22°C) [20]. The coupling chemical reaction of n-alkyl silanes with glass surfaces is shown in Fig. 1. Hydrolyzed alkyl silanes in aqueous solution can react with the silanol groups in the glass surfaces to produce immobilized alkyl chains. 

Considerable insight into the lateral cohesion of the floating monolayer can be obtained by examining the hysteresis of the isotherm. The greater the cohesion, the greater the hysteresis. To date, this is a rather nnderexploited approach to characterize partially compressed monolayers (i.e., at a pressure lower than jTc collapse is nsually an irreversible phenomenon). However, monolayer viscoelasticity (compression and shear moduli) has recently been determined by such an approach. ... 

Chaudhury, M. K., and Owen, M. J. (1993) Correlation between Adhesion Hysteresis and Phase State of Monolayer Films, J. Phys. Chem. 97, 5722-5726. 

The modification of the fluid interfaces due to surfactant adsorption strongly influences the interactions between fluid particles (droplets, bubbles) in dispersions. Frequently a thin liquid film is formed in the zone of contact of two fluid particles. The contact angle at the periphery of such a film is a measure for the interaction of the two opposite surfactant adsorption monolayers. When the latter adhere to each other, a hysteresis of the contact angle is observed, irrespective of the fact that the fluid interfaces are molecularly smooth. The properties of the thin liquid films are important for the flocculation in dispersions and the deposition (attachment-detachment) of particles at surfaces see Sec. V. 

The occurrence of sizable contact angle hysteresis on perfectly smooth surfaces was reported as early as 1952 by Bartell and Bjorklund [46] in a three-liquid, three-phase system comprising mercury, benzene, and water. A strong conclusion was not drawn that time presumably due to the observation of an unexplained, aging phenomenon on the three-liquid system. Four decades later, Chen and coworkers [47] reported a study of the contact angle hysteresis of several monolayer modified mica... 

Fig. XVll-19. Adsorption of CH4 on MgO(lOO) at 77.35 K. The vertical line locates each vertical step corresponds to the condensation of a monolayer. There was no hysteresis. Desorption points are shown as . (From Ref. 110.)...

---