Solvent and Temperature Effect
The statistics of a single polymer chain depends on the solvent. For good solvent the chain is more expanded while for bad solvent the chain segments stay close to each other. In the limit of a very bad solvent the polymer chain merely collapses to form a hard sphere, while in good solvent the chain swells in order to maximize the number of polymer-fluid contacts. For this case the radius of gyration is approximated using Flory's mean field approach which yields a scaling for the radius of gyration of:
-
- ,
where is the radius of gyration of the polymer, is the number of bond segments (equal to the degree of polymerization) of the chain.
For good solvent, ; for bad solvent, . Therefore polymer in good solvent has larger size and behaves like a fractal object. In bad solvent it behaves like a solid sphere.
In the so called solvent, which is the result of simple random walk. The chain behaves as if it were an ideal chain.
The quality of solvent depends also on temperature. For a flexible polymer, low temperature may correspond to poor quality and high temperature makes the same solvent good. At a particular temperature called theta (θ) temperature, the solvent behaves as if an ideal chain.
Read more about this topic: Polymer Physics
Famous quotes containing the words solvent, temperature and/or effect:
“Analysis as an instrument of enlightenment and civilization is good, in so far as it shatters absurd convictions, acts as a solvent upon natural prejudices, and undermines authority; good, in other words, in that it sets free, refines, humanizes, makes slaves ripe for freedom. But it is bad, very bad, in so far as it stands in the way of action, cannot shape the vital forces, maims life at its roots. Analysis can be a very unappetizing affair, as much so as death.”
—Thomas Mann (1875–1955)
“The bourgeois treasures nothing more highly than the self.... And so at the cost of intensity he achieves his own preservation and security. His harvest is a quiet mind which he prefers to being possessed by God, as he prefers comfort to pleasure, convenience to liberty, and a pleasant temperature to that deathly inner consuming fire.”
—Hermann Hesse (1877–1962)
“Reckoned physiologically, everything ugly weakens and afflicts man. It recalls decay, danger, impotence; he actually suffers a loss of energy in its presence. The effect of the ugly can be measured with a dynamometer. Whenever man feels in any way depressed, he senses the proximity of something “ugly.” His feeling of power, his will to power, his courage, his pride—they decline with the ugly, they increase with the beautiful.”
—Friedrich Nietzsche (1844–1900)