A new type of poly(ethylene glycol) [PEG] hydrogel network was synthesized that is crosslinked through silsesquioxane domains [SiO1.5] formed by hydrolysis and condensation of a bis(triethoxy silyl propyl urethane)-PEG-2000 precursor. Step crystallization-DSC and DMTA techniques were used to characterize the PEG domains in the dry network while silsesquioxane cross-link structures and connectivity were determined by Si-29 solid state NMR. No evidence was found by Si-29 NMR or TEM for the formation of silica domains [SiO2]. The concentration of added acid in the sol-gel reaction controls the kinetics of the silsesquioxane formation and thus the size of these domains. Water-swelling studies confirm that when the particles are formed slowly (at lower acid concentration) there is an increase in the cross-link density and connectivity; i.e. the number of chains attached to each silsesquioxane domain. High connectivity also reduces the crystallinity of PEG in the dry network and results in a shift in both alpha- and alpha'-transitions to lower temperatures.