The second derivative of the Gibbs free energy of mixing for a polymer/solvent p
ID: 911264 • Letter: T
Question
The second derivative of the Gibbs free energy of mixing for a polymer/solvent pair with respect to the volume fraction of polymer is changing sign from negative to positive and then again to negative as concentration of polymer increases at constant temperature and pressure. Chose right statement and briefly justify your answer. a.Polymer and solvent are partially miscible; b.Cannot judge without additional information; c.Polymer and solvent are totally miscible; d.Polymer and solvent are totally immiscible.
Explanation / Answer
Polymer and solvent are partially miscible because
The dissolution of a polymer into a solvent involves two transport processes, namely solvent diffusion and chain disentanglement. When an uncrosslinked, amorphous, glassy polymer is in contact with a thermodynamically compatible solvent, the solvent will diffuse into the polymer. Due to plasticization of the polymer by the solvent, a gel-like swollen layer is formed along with two separate interfaces, one between the glassy polymer and gel layer and the other between the gel layer and the solvent. After time has passed, an induction time, the polymer dissolves
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