Energetics of the Flow-Equilibrium

The high resolution of the PDC-column, as demonstrated in Table 6, can well be explained by the assumption that the flow-equilibrium is fully active for the 1082-mer at 15 °C in the system PS/CHX, whereas it is only weakly active for the 353-mer at this temperature. This assumption can additionally be supported by an investigation of the deformability of these macromolecules by the velocity gradient near the gel front (see Sect. 3.4). But first the energetics of the flow-equilibrium need to be investigated. 

The kinetic constants, calculated in the previous section, can immediately by applied to the investigation of the energetics of the flow-equilibrium, especially to the calculation of the activation enthalpy AH and entropy AS related to the coil relaxation in the actual gel phase as mentioned above, and to the coil release from segment-segment contacts with the gel, before the retarded rediffusion of these coils from the gel into the sol sets on. These thermodynamic functions can then be compared with those of the reversible polymer transfer gel - sol calculated in Section 3.1. 

According to Eq. (24) with a practically temperature-independent rate constant ks, as well as Eqs. (4), (7) and (10 a, b), the relationship 

Both expressions (29 a, b) reduce to the zero solvation term P = 0 at the theta point, where 8Q/K - 0, kg - kg and e, - 0 for any P. After eliminating it, the relationship between the chain contributions to the heat of polymer transfer gel - sol in a flow-equilibrium and in a reversible-thermodynamic equilibrium can be obtained  

Both terms on the right-hand side of this equation are always non-negative the quantity In (kg/k ) increases with decreasing temperature for any P, as can be seen from Table 5 or Fig. 18 e.g. the values 0.06 at 27 °C and 1.32 at 15 °C are obtained for P = 1082 according to Table 5. The second term is even greater than the first (reversible) one at low column temperatures it represents the irreversible part of the heat of transfer gel - sol in the flow-equilibrium proposed. Thus, both terms can be considered as the activation enthalpy of the retarded polymer rediffusion from the gel into the sol  

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