Adhesion acid-base interactions

Numerous reports of comparable levels of success in correlating adhesion performance with the Scatchard-Hildebrand solubility parameters can be found in the literature [116,120-127], but failures of this approach have also been documented [128-132J. Particularly revealing are cases in which failure was attributed to the inability of the Scatchard-Hildebrand solubility parameter to adequately account for donor-acceptor (acid-base) interactions [130,132]. Useful reviews of the use of solubility parameters for choosing block copolymer compatibilizers have been prepared by Ohm [133] and by Gaylord [134]. General reviews of the use of solubility parameters in polymer science have been given by Barton [135], Van Krevelen [114], and Hansen [136]. 

Vrbanac, M.D., Acid-Base Interactions in Adhesion and Wetting, Dissertation Thesis, University of Washington, 1989. 

Mittal, K.L. and Anderson, H.R. Jr. (Eds.), Acid-Base Interactions Relevance to Adhesion Sciertce and Technology. VSP, Utrecht, 1991. 

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. 

For the sake of completeness, it is worthwhile to briefly discuss role of acid-base interactions in adhesion. In this context, the term acid refers to a Lewis acid (an electron acceptor) and a Lewis base (electron donor), rather than the more conventional acid and base definitions. The role of acid-base interactions in adhesion is discussed in detail by Lee [105]. 

It should be intuitively obvious that the contribution to the work of adhesion arising from acid-base interactions cannot be expressed in terms of the geometric mean of the surface energies. Therefore, the entire work of adhesion would be... 

Upon combining Eqs. 88 and 85, one finds that the total work of adhesion is related to the surface energies of the contacting materials as well as the enthalpy associated with acid-base interactions by... 

It is known that the possible interaction between two materials 1 and 2 is determined by their surface energies, which consist of two components, dispersive, and specific or polar, y . When hydrogen bonding and acid-base interactions are also involved, the adhesion energy between the two materials, Wa will be" ... 

Basic Mechanisms of Adhesion Acid-Base Interactions. The understanding of polymer adhesion has been greatly advanced in recent years by the recognition of the central role of acid-base interactions. The concept of an acid was broadened by G. N. Lewis to include those atoms, molecules, or ions in which at least one atom has a vacant orbital into which a pair of electrons can be accepted. Similarly, a base is regarded as an entity which possesses a pair of electrons which are not already Involved in a covalent bond. The products of acid-base interactions have been called coordination compounds, adducts, acid-base complexes, and other such names. The concept that... 

Manson (72,) expanded the concept to the solid state by observing that the strength of composite materials also depended upon the acid-base interaction between continuous and dispersed phases. More directly, Vanderhoff et al. (21) addressed the issue of adhesion of polymeric materials to corroded steel. They synthesized eight corrosion products of iron, and used the interaction scheme developed by Fowkes and Manson first to characterize the iron corrosion products as Lewis acids or bases and then to select polymer vehicles for practical coating systems. Such results were employed to enhance the adhesion of epoxy systems to substrates which were predominantly iron oxide in nature. A good overview of these Issues was presented by Fowkes in 1983 (74). ... 

Fowkes and co-workers also clearly demonstrated that the physical Interaction of polymers with neighboring molecules was determined by only two kinds of interactions London dispersion forces and Lewis acid-base interactions (21) Calculations based on this concept were shown to correct many of the problems inherent in the solubility approach. They were also able to use the concept to study the distribution of molar heats of absorption of various polymers onto ferric oxides, and thereby more accurately described the requirements for adequate adhesion to steel substrates (21) In the symposium on which this book is based, Fowkes summarized work showing that the polar Interactions between polymers and metal surfaces that are... 

Although Eq. 11 tries to take into account the effect of polar interactions, the role of acid/base interactions in adhesion became clear and theories describing them have been more and more accepted [35]. The boimdary case of such interactions is the formation of covalent bonds between the surfaces. Such interactions cannot be described by Eq. 11. As a consequence Fowkes [36] suggested that the reversible work of adhesion should be defined as ... 

Mittal KL, Anderson HR (1991) Acid-base interactions relevance to adhesion science and technology. VSP, Utrecht... 

Fowkes, F. M., Quantitative characterization of the acid-base properties of solvents, polymers, and inorganic surfaces . In Acid-Base Interactions - Relevance to Adhesion Science and Technology, K. L. Mittal and H. R. Anderson, Eds., VSP, Utrecht, 1991, pp. 93-115. 

Acid-base reactions across the interface. This subject was well covered by a symposium on Acid-Base Interactions Relevance to Adhesion Science and Technology in honor of Professor F. M. Fowkes on his 75th birthday. Most of these papers have been published in Vol. 4, No. 4, No. 5 and No. 8 (1990) and Vol. 5, No. 1 (1991) of the Journal of Adhesion Science and Technology. 

Barthes-Labrousse MG, Joud JC (2000) Acid-Base Characterization of metallic materials and the use of model molecules in the study of adhesion mechanism. Acid-Base Interactions Relevance to Adhesion Science and Technology, Mittal KL (ed) VSP Utrecht, 453... 

Huang YC, Fowkes FM, Loyd TB (1991) Acidic and basic nature of ferric oxide surfaces. Adsorption, adhesion, zeta potential and dispersibility in magnetic inks for hard disks. In Mittal KL, Anderson HR (eds) Acid-Base-Interactions. VSP Utrecht, p 363... 

Also, Fowkes [26,148] actually developed a technique for the determination of the work of adhesion, WA, by applying a four-parameter equation for acid-base interaction in the system of solid-liquid using Eqs. (29) and (32)... 

By far the dominant adhesion mechanism, particularly in the absence of covalent linkages, is the electrostatic attraction of the polar groups of the adhesive to polar groups of the adherends. These are mainly forces arising from the interaction of permanent dipoles, including the special cases of hydrogen bonding (10-25 kJ/mol) and Lewis acid-base interactions (<80 kJ/mole).25 26 These forces provide much of the attraction between the... 

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