Secondary valence forces

The atoms of a molecule are held together by primary bonds. The attractive forces which act between molecules are usually referred to as secondary bonds, secondary valence forces, intermolecular forces or van der Waals forces. 

TPEs are materials that possess, at normal temperatures, the characteristic resilience and recovery from the extension of crosslinked elastomers and exhibit plastic flow at elevated temperatures. They can be fabricated by the usual techniques such as blow molding, extrusion, injection molding, etc. This effect is associated with certain interchain secondary valence forces of attraction, which have the effect of typical conventional covalent crosslinks, but at elevated temperatures, the secondary... 

Bonding forces Primary valence forces (intramolecular forces) Secondary valence forces (intermolecular forces)... 

Amylase operates exclusively on nonreducing, terminal units in amylose or on the branches in amylopectin, to produce maltose directly, and its hydrolytic action on 4 — 1-a-D linkages is stopped by any branch points. Enzyme action is greatly impeded by secondary valence forces, as retro-gradation, for example, is accompanied by an increased resistance to j8-amylolysis.19 The enzyme can be crystallized relatively easily. The mode... 

In polymer science and technology, linear, branched and crosslinked structures are usually distinguished. For crosslinked polymers, insolubility and lack of fusibility are considered as characteristic properties. However, insoluble polymers are not necessarily covalently crosslinked because insolubility and infusibility may be also caused by extremely high molecular masses, strong inter-molecular interaction via secondary valency forces or by the lack of suitable solvents. For a long time, insolubility was the major obstacle for characterization of crosslinked polymers because it excluded analytical methods applicable to linear and branched macromolecules. In particular, the most important structural characteristic of crosslinked polymers, the crosslink density, could mostly be determined by indirect metho ds only [ 1 ], or was expressed relatively by the fraction of crosslinking monomers used in the synthesis. 

It is well known from very early studies on lignin reactivity that hydrogen bond formation and other secondary valence forces strongly affect the... 

The polar groups in ionomers are suppressing the tendency of crystallization. Moreover, a ionic crosslinking is effected. Thus, both secondary valency forces and ionic forces are active. The special types of bonds effect a special toughness of the materials. However, ionomers are true thermoplastic materials. 

Visualizing Folded Protein Structures Primary Structure Determines Tertiary Structure Secondary Valence Forces Are the Glue That Holds Polypeptide Chains Together Domains Are Functional Units of Tertiary Structure Predicting Protein Tertiary Structure Quaternary Structure Involves the Interaction of Two or More Proteins... 

Secondary Valence Forces Are the Glue That Holds Polypeptide Chains Together... 

Secondary recycling, 191,193,194-195 Secondary valence forces, 58 Self-assembly, 216-218 Semicrystalline polymers, 138,140, 154 Sensors for smart materials, 207, 208, 218 Sequence distribution, 28 Serine, 29... 

Direct dyes are anionic colorants that have affinity for cellulosic fibers.17 They were the first dyes that could be used to dye cotton in the absence of a mordanting agent, giving rise to the term direct-cotton dyes. Like acid dyes, direct dyes contain one or more -SOjNa groups, making them water-soluble. Unlike acid dyes, they interact with cellulose (Cell-OH) chains via secondary valency forces (e.g., H-bonding and dipole-dipole interactions), as illustrated in... 

ES is called the Michaelis complex, in which substrate molecules are bound to the active site by various secondary valence forces. The structure of Michaelis complexes is directly related to the efficiency and specifidty of the enzymatic catalyds. The apparent rate of catalysis is expressed by... 

The solvolysis of short-chain substrates (PNPA 3, NABA 6 NABS 3, etc.), when catalyzed by imidazole-containing homopolymers, usually follows the second-order kinetics. This implies that secondary-valence-force attractions, if operating, are not sufficient to cause substrate binding to a kinetically observable extent. The macro-molecule-substrate complexation, once proposed for the polyvinylimidazoIe-NABS system, (54) was shown to be an artifact caused by slow deacylation (55). 

Enclosure by complex formation with cage compounds like cyclodextrins, fixed with primary or secondary valence forces to the fibre surface, release by evaporation or displacement... 

Most of the above results are in accord with the idea that xylan and cellulose co-exist in a sort of mixed crystallization" held together by secondary valence forces (such as hydrogen bonds). Mechanical treatment w ould be expected to disrupt such bonds, thus decreasing the resistant xylan, and the removal of water from a wet pulp would allow neighboring chains to come into contact, resulting in augmentation of the number of secondary bonds and thus increasing the resistant xylan. 

By this time, Hermann Staudinger and Wallace H. Carothers had firmly established that primary (not secondary) valence forces are involved in polymerization. Hibbert and his coworkers then synthesized a series of individual, linear polymers, each of known chain-length, and studied their properties as a function of chain length. The kind of reaction used in these syntheses, for polymers containing 4, 6, 8, 12, 18, 42, 90, and 186 units, was as follows. 

The forces responsible for adhesion/release are intermolecular, and are usually referred to as secondary valence forces. In many cases, however, they can also be primary, that is, those of direct chemical bond. In any event, the force of separation Fs is shown to be a function of two factors work of adhesion Wa, and the distance of bond separation d. Taylor and... 

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