Abstract: A silane or carbosilane dendrimer is modified with bridge moieties and polymer arms attached to the bridges to form hybrid dendrimer-star polymers. The bridge moieties are attached via Si—C bonds to the silane or dendrimer. The bridge has one or more reactive groups to which polymer arms are attached. Selected reactive groups on the bridge may serve as initiator sites for in situ polymerization of the arms. The polymer arms are of the polyether, polysulfide or polyester type. These arms may have functional groups which allow further modification and attachments. For this type of star polymer, the bridge has been found to increase resistance to hydrolysis at the silane- or dendrimer-arm junction. These star polymers are useful e.g. as viscosity modifiers, component in molding resins, water solubilizer for hydrophobic molecules, surfactants and as carriers for drugs, prodrugs and other biological agents.