This paper discusses the effect of heterogeneities in crosslink densit
y on static properties, such as the mechanical stress-strain relation
(free energy) and scattering effects as occur in small-angle neutron e
xperiments- The second part of the paper is devoted to the segmental d
ynamics and the long-time relaxation of polymer networks. It is shown
that the heterogeneities slow down the relaxation at long times.