Random units, polymer description

An illustrative description of the ineffective cycles is provided by the network polymer random model8,187>. The model is underlied by a conception of the network polymer structure as a combination of the accidentally associated cycles with a certain distribution by size. Scheme (27) illustrates the first members of a series of cyclic structures formed by reaction of the diepoxides with diamines (the notation i, j means a ring composed of i diepoxide and j diamine units)... 

Only when polymer chains form part of a crystal lattice can a precise structure be specified for the sample. In such a case the system can be defined by copying the contents of the unit cell along directions parallel to the lattice vectors. But polymers by their nature depart drastically from this ideal. Motions in noncrystalline media are subject to so many random or indeterminable factors that they cannot be treated by methods that require specifying a precise structure. Nevertheless we include a brief account of how randomness can be introduced into the simulation of polymer systems, since results have been shown to produce useful descriptions of noncrystalline polymer states. For more details about the methods, we refer the reader to books and specialist review articles " and descriptions of polymer simulation codes. " " ... 

---