8.5 Crosslinked Polymers

A crosslinked or network polymer is one in which chemical linkages exist between the chains，as illustrated in Figure 8-2. Such materials are usually swelled by "solvents"，but they do not dissolve. In fact，this insolubility can be used as a cautious criterion of a crosslinked structure. Actually，the amount by which the polymer is swelled by a liquid depends on the density of crosslinking，the more crosslinks present，the smaller is the amount of swelling. If the degree of crosslinking is high enough，the material may be a rigid，high-melting，unswellable solid，such as diamond. Light crosslinking of chains favors the formation of rubbery elastomeric properties.

Figure 8-2 Crosslinked Polymer