ISSN:
0022-3832
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The molecules of high-molecular substances, for instance, those present in rubber, can be treated statistically in two ways. On the one hand, these molecules are such complicated structures that it is possible to attribute a separate entropy and free energy to each giant molecule. On the other hand, solutions of high-molecular substances represent systems in which the single chain molecule is the elementary particle, and to which statistical considerations and concepts such as entropy and free energy can be applied. Depending upon the parameter considered, the same chain molecule must sometimes be treated as a complicated system and at other times as an elementary particle. The problems originating from the simultaneous existence of two stages in the statistical treatment are examined. It is shown that the entropy of an assembly of many chain molecules is not simply equal to the sum of the entropies of the separate chain molecules. This becomes apparent particularly when determining the distribution function with respect to a particular parameter (e.g., distance between the two end points of a molecule) from a statistical consideration of the single molecule on the one hand, and from a consideration of an assembly of identical molecules on the other hand. The relations between entropy and free energy of the individual particle and the a priori probabilities on which the treatment of an assembly is to be based are explained. It is further shown that the same particle can give rise to a macroscopic phenomenon in two ways and to approximately the same extent: first, as a complicated system, and second, as an element in a large assembly of identical particles. This applies in particular to the elastic retractive force and to the strain birefringence in rubber and related substances.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1946.120010306
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