Читать книгу Adhesives for Wood and Lignocellulosic Materials - R. N. Kumar - Страница 50

An ion-dipole force is an attractive force that results from the electrostatic attraction between an ion and a neutral molecule that has a dipole. It is most commonly found in solutions. It is especially important for solutions of ionic compounds in polar liquids. The potential energy of ion–dipole interaction is given by

where q is the charge on the ion.

One should note that in all the above equations describing the intermolecular attractions, the denominator contains the factor r⁶. Thus, the types of intermolecular interactions described above occur only at very small distances, of the order of typical atomic bond lengths (the range of non-bonding interactions is between 0.3 and 0.5 nm). For interactions to occur, therefore, the two materials must be able to make intimate contact with each other (i.e., they must be able to approach within a nanometer). This is possible if the adhesive wets the substrate efficiently. The types of interactions and the corresponding energies are given in Table 2.1.

Table 2.1 Bond types and typical bond energies [1].

Type of interaction	Energy (kJ/mol)	Basis of attraction
Bonding
Ionic	400–4000	Cation–anion
Covalent	150–1100	Nuclei–shared electron pair
Metallic	75–1000	Cations–delocalized electrons
Non-Bonding
Ion–dipole	40–600	Ion charge–dipole charge
Hydrogen bonding	10–40	Polar bond to hydrogen–dipole charge
Dipole–dipole	5–25	Dipole charges
Ion–induced dipole	3–15	Ion charge–polarizable electrons
Dipole–induced dipole	2–10	Dipole charge–polarizable electrons
Dispersion forces	0.1–40	Interaction between polarizable electrons