Solvating envelope

Nonradiative relaxations in solutions are particularly interesting. Terpi-lovskii (38) made a calculation of the probabilities of nonradiative transitions for the trivalent terbium ion in aqueous solution. He considered that the transitions were caused by Brownian movement of vibrations of the solvate envelope. 

Free of such troubles is model (b) of the solvation envelope between the actual sol and gel it leads to a trivial integration of the diffusion equation The corresponding boundaries... 

All the enumerated examples indicate the insufficiency of reactions (59)-(64) to explain completely the initiation of cationic polymerizations. An inseparable aspect of initiation is the activation of the primary products produced by ionization or dissociation. Several kinds of ion pair of various reactivities are known to exist. The solvate envelope of free ions must affect the frequency of active ion-monomer collisions, i. e. the initiation rate. In the author s opinion, the key to our understanding of some co-initiation effects in cationic polymerization is a suitable interpretation of the Winstein dissociation scheme [247]... 

Metal-containing polymers may be produced by various methods, such as chemical reactions of precursors— in particular, reactions of metal salts in polymer solutions, the treatment of polymers with metal vapors, or the polymerization of various metal-monomer systems [1-4], Depending on the metal nature and the polymer structure, these processes lead to organometallic units incorporated into polymer chains, metal-polymer complexes, or metal clusters and nanoparticles physically connected with polymer matrix. Of special interest are syntheses with the use of metal vapors. In this case, metal atoms or clusters are not protected by complexones or solvate envelopes and consequently have specific high reactivity. It should be noted that the apparatus and principles of metal vapor synthesis techniques are closely related to many industrial processes with participation of atomic and molecular species [5]—for example, manufacturing devices for microelectronic from different metals and metal containing precursors [6]. Vapor synthesis methods employ varying metals and... 

The solvation of the chain of a polymer has a big impact on the expansion of the polymer coil. Figure 5.2 shows that a big solvating envelope increases the effective volume of a polymer segment and therefore the volume fraction of the polymer coil. This leads to a decrease of the polymer density in solution according to... 

The solvating envelope of the polymer chain can increase when the polymer-solvent interaction (solvent quality) increases with the temperature. The rising solvation of the chain leads to an expansion of the polymer coil and therefore to an increasing intrinsic viscosity. Figure 5.7 shows this increase of the intrinsic viscosity with the temperature for poly(acrylamide) in aqueous solution. The zero-shear viscosity of the same sample decreases with the temperature in Fig. 5.5. 

The intrinsic viscosity [r ] of a polymer increases with rising solvent quality (see Solvent in Chap. 5) due to the increased solvating envelope of the polymer chain. An increased effective volume of the chain leads to an expansion of the polymer coil and therefore to an increased intrinsic viscosity (see Fig. 5.2). The solvent quality can also be seen in the exponent a of the [q]-M-relationship. In the case that the interactions of the solvent molecules with the chain are so small that the coil is not contracted or expanded, theta-conditions are reached and the coil has its unperturbed dimensions in solution. A theta solvent is referred to as a thermodynamically poor solvent. In this solution state a theoretical value for the exponent a=0.5 can be derived (the required Eqs. 8.22 and 8.33 are discussed in detail in A deeper insight into in Chap. 8). This value of a=0.5 is also experimentally observed as shown in Fig. 6.7 for the theta system poIy(styrene) in cyclohexane (T=34.5 C). 

This behavior is probably caused by a rising influence of the chain ends. Below a critical molar mass, the number of polymer segments is too low to form a flexible coil. In addition to this, short polymer chains have no excluded volume and the influence of the solvation envelope on the coil expansion disappears. In addition, coil substructures like helical parts have an effect on the overall coil structure above a critical number of polymer segments. 

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