Polymer crystallization Gibbs free energy

Which component of Gibbs free energy (entropy or enthalpy) drives crystal formation in a polymer How ... 

Flow imparts both extension and rotation to fluid elements. Thus, polymer molecules will be oriented and stretched under these circumstances and this may result in flow-induced phenomena observed in polymer systems which include phase-changes, crystallization, gelation or fiber formation. More generally, the Gibbs free energy of polymer blends or solutions depends under non-equilibrium conditions not only on temperature, pressure and concentration but also on the conformation of the macromolecules (as an internal variable) and hence, it is sensitive to external forces. 

FIGURE 15.20 Gibbs free energy G versus temperature T for liquid and various crystal forms of triglycerides, (a) General trend for the main polymorphs, (b) Observed trends for SOS. (Results taken from K. Sato. Progr. Colloid Polym. Sci. 108 (1988) 58.)... 

It has been observed that the crystallization behavior of polymers is modified when the material is strained. This behavior has been found in rubbers and in thermoplastics [14]. In thermoplastics, the effect of strain on crystallization behavior has been studied quite extensively in solutions, in melt, and in solid state. For instance, it has been found that flowing polymer melts can crystallize at temperatures that are substantially above the crystallization temperature of the same material in a quiescent state. This strain-induced crystallization is generally explained in terms of thermodynamic processes. During a phase change, the Gibbs free energy is ... 

The axial oscillation and rotation of polymer chains in the crystal lattice yield at any temperature a minimum of Gibbs free energy at a finite long period L which in linear polyethylene (PE) for a reasonable choice of surface free energy well agrees with the experimentally observed lamella thickness. ° °... 

Gibbs free energy density of the phase of A/B-chains Gibbs free energy of a polymer chain chemical potential of a monomer in the melt chemical potential of a monomer in an infinite crystal difference in the chemical potential between phases i and j (= 9j - 9i)... 

Most polymers of regular structure will crystallize if cooled below the melting point, Tm. This is in accordance with the thermodynamic law that a process will occur only if there is a decrease in Gibbs free energy (—AG) in going from one state to another. Such a decrease occurs on crystallization as the molecules pack in a regular fashion. Since a process occurs only when it is accompanied by a decrease in free energy, there is no reason why a crystalline nonpolar polymer should dissolve in... 

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