Surface free energy changes

Here AFu is the standard free energy change per repeat unit on melting, and ae is the surface free energy change per chain at the ends of the crystallite. It can be shown that the surface free energy associated with lateral surfaces may be ignored in the present case. 

Ramos-Tejada, M.M. et al.. Investigation of alumina/(-l-)-catechin system properties. Part II. potential and surface free energy changes of alumina. Colloids Surf. B. 24, 309, 2002. 

A third type of wetting is immersional wetting, where a substrate not previously in contact with a liquid is immersed completely by the liquid (Figure 6-5). In this case, the surface free energy change per unit area is... 

The surface free energy change per unit area or driving force for the three different types of wetting can be expressed as... 

Since Pf, > Pv, dG is negative and the process is spontaneous. This free-energy change can also be calculated from the surface free-energy change of the droplet, which results from the surface area decrease due to the loss of dn mol of the liquid having a molar mass of Mw. This evaporation process produces a volume decrease of -d (JVfw/pi.) in the liquid drop. As a result of this volume decrease, a spherical shell from the drop surface whose volume is = Ajzfdr is lost from the total drop volume. Then we can write... 

The Helmholtz surface free-energy change due to the formation of a monolayer is the difference between the Helmholtz free energy of the pure solvent surface and that of the solution surface (ymonola) er = FS- Ps0). The Helmholtz free energy at the surface was defined... 

Surface Free Energy Changes in Protein Aggregation... 

Figure 4. The calculated values of the equilibrium constant (%) in units of k = zlFs/RT, the surface free energy change due to the conformational change, superimposed upon the dashed curve of the Bohr effect in units of log P0 5, the oxygen pressure for half saturation of hemoglobin. The sets of values are made to coincide at pH 6.3 and are in the same units over the same pH range. (Reproduced with permission from reference 8. Copyright 1975.)...

Fig. 10.24 Illustration of total surface free energy change in homogeneous nucleation and heterogeneous nucleation...

There is also another type of primary nucleation called self-nucleation investigated first by Blundell et al. (1966). The foreign surfaces for self-nucleation are provided by crystals of the same species which survived during thermal history. Since there is no extra surface free energy change during self-nucleation, it is also called athermal nucleation. This type of nucleation is an important source of memory effects for polymer crystallization. 

Figure 6. Schematic of the system Teflon/n-hexane - air - water for determination of surface free energy changes of Teflon wetted with n-hexane film. Symbols T - Teflon, f - n-hexane film, w -water.

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