this invention provides water - swellable articles and hydrogels that contain a hydrophilic polymer and perfluorocyclobutane crosslinking segments . the perfluorocyclobutane crosslinking segments are covalently attached to the polymeric chains of the hydrophilic polymer so that the crosslinking segments chemically link the polymeric chains to each other . the present invention also provides a method of making a crosslinked hydrogel by first attaching one or more substituted aromatic trifluorovinyl or aromatic trifluorovinyl ether moieties to a hydrophilic polymer to form a modified polymer and then heating the modified polymer at an elevated temperature to form perfluorocyclobutane segments from the trifluorovinyl or trifluorovinyl ether moieties . these water - swellable articles and hydrogels may be used in biomedical and pharmaceutical applications and may be suitable for implanted joint repair materials such as an articulating or bearing surface in a hip , knee , spine , finger , ankle , elbow , wrist , or shoulder joint .