Acid-base interactions and adhesion

Polymer Surfaces and Interfaces Acid-Base Interactions and Adhesion in Polymer-Metal Systems... 

Polymer Surfaces and Interfaces Acid-Base Interactions and Adhesion in Polymer-Metal Systems Irina A. Starostina, DSc, Oleg V. Stoyanov, DSc, and Rustam Ya. Deberdeev, DSc... 

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

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]. 

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 ... 

Dispersive and specific interactions are considered to contribute independently to the adsorption of probe molecules at the adsorbent surface. It was presented that the adhesion of the fibre-matrix interface depends clearly on the measured strength of acid/base interactions of both fibre and polymer-matrix. Fowkes [2,3] indicated also that the surface of fillers can be chemically modified to enhance acid-base interaction and increase adsorption. 

The aim of the present contribution is to review the role of acid-base interactions in adsorption, wetting, and adhesion, and the methodologies and techniques to characterize the acid-base properties of materials. Examples have been selected from the authors research work and from a survey of the literature. This chapter is organized into the following three sections definition, properties, and strength of acid-base interactions theory of acid-base interactions in adhesion and experimental assessment of acid-base properties of polymers and other materials. 

The background to acid base interactions in adhesion science and technology has been reviewed with the emphasis on polymers, metal oxides, fillers, fibers, and pigments. When... 

Finally, AFM appears as an extraordinary technique to study acid-base interactions at the molecular scale. It enables the determination of pXa for surface confined carboxylic and other Bronsted groups. With the systematic studies which have appeared over recent years using thiol-treated tips and surfaces, clearly AFM has become a very well established and powerful tool for fundamental and applied research studies on acid-base interactions in adhesion. 

Acid/Base Interactions and the Adhesion of PUs to Polymer Substrates... 

Any attempt to relate acid/base interactions between adhesives and substrates to the bond properties of the relevant pair depend on a quantitative evaluation of a pair interaction parameter. There are no broadly accepted theoretical guidelines to such an evaluation, but a pair interaction parameter, I p, can be defined by... 

The article on Surface energy components describes how surface energies of solids and thence the work of adhesion between adhesive and substrate could be calculated from an assumption that the surface energy is composed of the sum of a dispersion and polar component (Eqn. 9 therein). Practical measurements of surface tensions of liquids and of contact angles of liquids on solids were involved. In a similar way, solid surface energies and works of adhesion can be obtained from the assumption (Eqns. 3 and 4 above) that surface energy is made up of the sum of a Lifshitz-van der Waals and an acid-base component. The term is obtained using non-polar liquids in exactly the same way as the dispersion components, y, were obtained. This article is concerned with expressions that can be used to represent acid-base interactions and which can then be used in equations such as 3 and 4 and those derived from them. 

The first discussion of acid-base interactions in adhesion science was due to Bolger and Micheals. These authors described Bronsted-Lowrey interactions at oxide/ organic interfaces by means of standard equilibrium... 

The following subjects, which are related to surface energy, are included in this discussion wettability, acid-base interaction, and work of adhesion. The interrelation is well illustrated by the set of equations. 

For particle adhesion, the total forcesUOS) consist of Lifshitz-van der Waals forces the electrostatic induced image forces the capillary force F, the chemical forces ch (such as the acid-base interaction), and the double layer force F ... 

One method which has been used to characterize interfacial forces is based on specific donor-acceptor (acid-base) interactions between adhesive and substrate molecules. Here, functional groups in each material are assigned an acid or base strength, which then can be used to calculate expected bond strengths. Further discussion of this approach is delayed to a later section. 

Osterhold and Armbmster (1998) used the van Oss-Good theory in the study of adhesion changes due to surface modification (see Figure 6.14). Adhesion phenomena and their relation to acid-base interactions and other theories are also summarized by Clint (2001a,b). He showed that adhesion calculated from theories can be linked to experimental values. He presented results with both the van Oss-Good and Owens-Wendt theories but recommends the former for polar systems. 

Fowkes himself became later convinced of the importance of acid-base interactions and related them to Drago s acid-base parameters (showing that 23% of the work of adhesion for water-aromatics can be due to acid-base interactions). 

It is some 60 years ago that Lewis [78] proposed that bases are electron donors and acids are electron acceptors. More recently, Fowkes and co-workers [79-83] have treated hydrogen bonds as a subset of Lewis acid-base interactions and suggested that interfacial acid-base bonds between the adhesive and the substrate may often play a key role in adhesives technology. 

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]. 

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