A new structural parameter of polymers–the relative number of network bonds per unit volume



In this paper we define a new structural parameter of polymers, and show how this may be employed. This parameter, for which only the structure and the density are needed, is the relative number of network bonds per unit volume; it is written Ner (basis 1 cm3), and it is used in conjunction with the average connectivity or connection number CN of the network atoms, where the word connection also refers only to network bonds. The relationship of these two numbers makes it possible to present a unified picture of all polymers, organic and inorganic, including such highly condensed networks as diamond. By plotting Ner against CN, the region in which inorganic and organic polymers occur can be seen. This is called the polymer zone, and it is evident that carbon polymers occupy only a small part of it. From this graph, an arbitrary measure of bond packing efficiency can be deduced for carbon polymers. In addition, the process of graphitization and carbonization can be followed graphically within the polymer zone. Ner is also related to certain physical properties such as bulk modulus, hardness, and cubical coefficient of expansion, which depend (among other things) on the tightness of bond arrangement. The resultant correlations can be used to predict the value of Ner required to achieve given values of these properties for the more rigid structures.