Hydrogen bonding cohesive

The hydrogen-bonding cohesive energy contributiorldH, are also considered additive, and its component of the solubility parameter is estimated using ... 

Ejj, Ep, Ejj dispersion cohesion energy, polar cohesion energy, and hydrogen bonding cohesion energy, respectively. 

Hansen [137-139], and later van Krevelen [114] proposed the generalization of the solubility parameter concept to attempt to include the effects of strong dipole interactions and hydrogen bonding interactions. It was proposed that the cohesive energy density be written as the sum of three terms, viz. 

A significant step towards commercial success came with a discovery in the late 1950s by E. Ulrich at 3M when he found that copolymerization of hydrogen bonding monomers, like acrylic acid with alkyl acrylates resulted in cohesively strong, yet tacky materials [63]. Since then, newer developments in such areas as polymer crosslinking, and the synthesis and copolymerization of new monomers, have led to a rapid penetration of acrylics throughout the PSA industry. 

These types of polar monomer provide sites for hydrogen bonding which increase the cohesive strength of the PSA because of strong inter-chain interaction, and they can also allow for hydrogen bonding or other polar interactions with some substrates. 

As the amount of acrylic acid in the polymer increases, the degree of hydrogen bonding between polymer chains also increases causing the cohesive strength to improve without the need for crosslinking. Very similar observations can be made for other polar monomers, such as acrylamide. 

If the principal cohesive forces between solute molecules are London forces, then the best solvent is likely to be one that can mimic those forces. For example, a good solvent for nonpolar substances is the nonpolar liquid carbon disulfide, CS2-It is a far better solvent than water for sulfur because solid sulfur is a molecular solid of S8 molecules held together by London forces (Fig. 8.19). The sulfur molecules cannot penetrate into the strongly hydrogen-bonded structure of water, because they cannot replace those bonds with interactions of similar strength. 

Liquids without dipole moments (alkanes) have quite low cohesive energy densities, whereas hquids with dipole moments or hydrogen-bonding groups have high cohesive energy densities. 

Because of the electric interaction, hydrogen-bonded molecules hold on to each other more tightly than those in substances with pure covalent bonds. This cohesiveness is why water is a liquid at room temperature, whereas heavier covalent-bonded molecules such as chlorine, in the form of CI2, are gases. 

In its solid state, however, the basic structural features of ordinary hexagonal ice (ice I) are well established. In this structure (Figure 1.2), each water molecule is hydrogen bonded to four others in nearly perfect tetrahedral coordination. This arrangement leads to an open lattice in which intermolecular cohesion is large. 

The properties of organic liquids relevant to their use as solvating agents have also been reviewed [76]. The ability of liquids to solvate a solute species depends mainly on their polarity and polarizability properties, ability to hydrogen bond, and cohesive electron density. These molecular properties are best measured by the Kamlet-Taft solvatochromic parameters, and the square of Hildebrand s solubility parameter. 

To illustrate the application of the imf and steric parameters we consider cohesive energies of MeX at 298.15 K taken from the compilation of Majer and Svoboda73. The data set (Table 9) contains no compounds capable of hydrogen bonding. We have therefore used the IMF equation in the form ... 

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