Interfacial interactions studies

In the past few years, many reports have described the distinct advantages of luminescent silica nanoparticles over traditional dye molecules [54, 55]. These advantages allow their convenient use as fluorescent probes for applications ranging from biosensors [56, 57] to interfacial interaction studies such as immunoassays [58], multiplexed bio-analysis [59-61], nucleic acid analysis [62] and drug delivery [63] to name but a few (Fig. 6). 

The study of acid-base interaction is an important branch of interfacial science. These interactions are widely exploited in several practical applications such as adhesion and adsorption processes. Most of the current studies in this area are based on calorimetric studies or wetting measurements or peel test measurements. While these studies have been instrumental in the understanding of these interfacial interactions, to a certain extent the interpretation of the results of these studies has been largely empirical. The recent advances in the theory and experiments of contact mechanics could be potentially employed to better understand and measure the molecular level acid-base interactions. One of the following two experimental procedures could be utilized (1) Polymers with different levels of acidic and basic chemical constitution can be coated on to elastomeric caps, as described in Section 4.2.1, and the adhesion between these layers can be measured using the JKR technique and Eqs. 11 or 30 as appropriate. For example, poly(p-amino styrene) and poly(p-hydroxy carbonyl styrene) can be coated on to PDMS-ox, and be used as acidic and basic surfaces, respectively, to study the acid-base interactions. (2) Another approach is to graft acidic or basic macromers onto a weakly crosslinked polyisoprene or polybutadiene elastomeric networks, and use these elastomeric networks in the JKR studies as described in Section 4.2.1. 

Interfacial interaction between silicone and protein/starch microparticle, 3 and the use of polysiloxanes having hydrophilic groups for the stabilization of proteins against denaturation, 4 were studied. 

At the air-water interface, water molecules are constantly evaporating and condensing in a closed container. In an open container, water molecules at the surface will desorb and diffuse into the gas phase. It is therefore important to determine the effect of a monomolecular film of amphiphiles at the interface. The measurement of the evaporation of water through monolayer films was found to be of considerable interest in the study of methods for controlling evaporation from great lakes. Many important atmospheric reactions involve interfacial interactions of gas molecules (oxygen and different pollutants) with aqueous droplets of clouds and fog as well as ocean surfaces. The presence of monolayer films would thus have an appreciable effect on such mass transfer reactions. 

Chen and Abruna [104] have studied, using ac and dc cyclic voltammetry, interfacial interaction between the adsorbed porcine pancreatic phospholipase Ai and mercury. The authors have proposed reaction mechanism based on the interaction of cystine residues (disulfide) with mercury. They have found that surface reactions are complex and that several factors influence their mechanism. Their results and observations agree with the reaction pathway postulated for the... 

A simple linear plot of the data allows AA to be obtained. The results of a set of experiments (Table 5) are surprising. AA is independent of the size or molecular weight of the protein. Although the cross-sections of the proteins studied range from 1000 to 10,000 A2, AA is nearly constant at 100 to 200 A2. Conclusion . . only a small portion of the protein molecule needs to enter the interface in order for adsorption to then proceed spontaneously (Ref.3), p. 290). It is as if only a small foothold or handhold is required to stabilize the molecule against desorption. Now firmly planted at the interface, the molecule can optimize its interfacial interactions by time-dependent orientation and perhaps conformational changes. The size of the foot is obviously relevant to the exchange discussion in Sect. 4.5. 

Several studies of polymer/silane coupling agent interphases have involved the use of scanning electron microscopy (SEM) [5-7]. For example, Vaughan and Peek [6] have used SEM to examine fracture surfaces to determine the mode of failure of composite materials and to draw conclusions about interfacial interactions of various coupling agents and epoxide and polymer resin systems. 

Solid soils are commonly encountered in hard surface cleaning and continue to become more important in home laundry conditions as wash temperatures decrease. The detergency process is complicated in the case of solid oily soils by the nature of the interfacial interactions of the surfactant solution and the solid soil. An initial soil softening or "liquefaction", due to penetration of surfactant and water molecules was proposed, based on gravimetric data (4). In our initial reports of the application of FT-IR to the study of solid soil detergency, we also found evidence of rapid surfactant penetration, which was correlated with successful detergency (5). In this chapter, we examine the detergency performance of several nonionic surfactants as a function of temperature and type of hydrocarbon "model soil". Performance characteristics are related to the interfacial phase behavior of the ternary surfactant -hydrocarbon - water system. 

Prior to this discovery, in 1954 Silberberg and Kuhn (62) were first to study the polymer-in-polymer emulsion containing ethylcellulose and polystyrene in a nonaqueous solvent, benzene. The mechanisms of polymer emulsification, demixing, and phase reversal were studied. Wetzel and Hocks discovery would then equate the pressure-sensitive adhesive to a polymer-polymer emulsion instead of a polymer-polymer suspension. Since the interface is liquid-liquid, the adhesion then becomes one type of R-R adhesion (35, 36). According to our previous discussion, diffusion is not operative unless both resin and rubber have an identical solubility parameter. The major interfacial interaction is physical adsorption, which, in turn, determines adhesion. Our previous work on the wettability of elastomers (37, 38) can help predict adhesion results. Detailed studies on the function of tackifiers have been made by Wetzel and Alexander (69), and by Hock (20, 21), and therefore the subject requires no further elaboration. 

In a physically confined environment, interfacial interactions, symmetry breaking, structural frustration, and confinement-induced entropy loss can play dominant roles in determining molecular organization. Wu[295] studied the confined assembly of silica-copolymer composite mesostructures within cylindrical nanochannels of porous anodic... 

Mechanical Tensile Studies. The simple stress vs. strain characteristics of two-phase materials and their variation with relative phase composition can usually be given straightforward interpretation in terms of critical underlying structural factors. Among these factors can be listed topological connectivily of, and interfacial interaction between the phases. 

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