Gibbs free energy polymeric

We have already seen that the degree of polymerization of the melt is controlled by the amount of silica in the system (see, for instance, figure 6.4). If we mix two fused salts with the same amount of silica and with cations of similar properties, the anion matrix is not modified by the mixing process and the Gibbs free energy of mixing arises entirely from mixing in the cation matrix—i.e.. 

MICROTUBULE ASSEMBLY/DISASSEMBLY KINETICS. Cellular microtubules must undergo turnover, and nucleotide hydrolysis appears to play a central role in priming microtubules for their eventual disassembly. Two fundamentally different assembly/disassembly mechanisms persist during what has been termed steady-state polymerization both rely on GTP hydrolysis to provide a source of Gibbs free energy to sustain the steady-state condition . ... 

The Gibbs free energy relationship for a reversible process at constant temperature for polymerization is described by... 

One of the main problems in the selection of a cure cycle is to achieve control of the exothermic polymerization reaction, particularly for the case of large parts. The exothermic character of the polymerization reaction arises from the evolution of the Gibbs free energy ... 

AGpoi, polymeric interaction This results in a total interaction Gibbs free energy... 

The free energy change due to polymerization is equal to the difference of the Gibbs free energies of the polymer segment and the monomer molecule ... 

This study revealed that under microwave conditions polymerization phenomena such as polymerization selectivity, polymerization temperature shift, and polymerization temperature shift as a result of the microwave power setting, can be observed when products are compared with those obtained under conventional conditions. To explain these phenomena it was proposed that a new dipole partition function is present in the microwave field, so values of thermodynamic properties such as internal energy and Gibbs free energy of materials with permanent dipole moments change under microwave conditions, which in turn leads to shifts in the reaction equilibrium and kinetics compared with conventional conditions at the same temperature [46]. 

In the case of true thermodynamic phase equilibrium, in which the absolute minimum is attained for the system Gibbs free energy at given T and p, the solubility calculation is performed following the classical thermodynamic result which imposes the equality between the equilibrium chemical potential of the penetrant in the polymeric mixture and in the external phase Th equilibrium solute content, and... 

The symbol represents the Gibbs free energy of the polymeric mixture per unit polymer mass. 

For the solubility in glassy phases, the situation is substantially different since the polymer density does not match its equilibrium value p, but it finally reaches an asymptotic value determined by the kinetic constraints acting on the glassy molecules, and is substantially dependent on the past history of the polymer sample. Thus the penetrant concentration in the polymeric phase reflects the pseudo-equilibrium state reached by the system. In view of the NET-GP results, such pseudo-equilibrium condition corresponds to the minimum Gibbs free energy for the system, under the constraint of a fixed value (the pseudo-equilibrium value) of the polymer density in the condensed phase ... 

Consider the molar Gibbs free energy of mixing for a polymer solution, AG. Evaluate AG for a polymer with degree of polymerization T2 = 1000 at a polyma- concentration <1)2 = 0.2, when ... 

In the predominant number of cases, both the enthalpy and entropy of polymerization are negative. The term —TAS° becomes more positive with increasing temperature, until, at the transition temperature, the Gibbs free energy is equal to zero. Since no polymerization is possible above this temperature, this transition temperature is called the ceiling temperature. 

The second classification has been recently used in a later review article by Meijer and co-workers. This classification is mainly concerned with the mechanism of supramoiecuiar polymerization, which has been defined as the evolution of Gibbs free energy as a function of monomer conversion to polymer (p) from zero to one (p = 0 1) as the concentration, temperature, or some other environmental parameter is altered. This classification has been extremely effective in describing the vast array of examples of SPs, correlating mechanistic similarities with their covalent counterparts, which are widely understood to be classified mechanistically. In this scheme, the authors clearly identify the most fundamental difference between covalent and SPs as the difference in kinetic versus thermodynamic control. The authors argue that it is from this dramatic difference between covalent polymers and SPs, due to the reversibility of the noncovalent interactions, that SPs derive their special properties. This review did not include, however, SPs made from large macromolecular building blocks. 

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