Thermodynamics of Swelling in Glassy Amorphous/Crystalline Polymers in Water Vapor

Swelling of amorphous/crystalline polymers is a complex phenomenon, accompanied by a change in the internal energy of the polymer, the absorbate, and the solid solution, and also by transition of the polymer from the glassy state to the rubbery (high elasticity) state. The derivative of the internal energy (a thermodynamic characteristic of the solid solution) is the internal pressure. The excess internal pressure is the basic characteristic of the swelling process: the swelling pressure. We have analyzed the behavior of the change in swelling pressure, the common features and differences from swelling of gels and from osmotic phenomena.