Poly(lactones) may be crosslinked by ring-opening polymerization of the corresponding cyclic esters in the presence of tetrafunctional bis(epsilon-caprolactone). The homopolymer of 1.5-dioxepan-2-one (DXO) has poor mechanical properties but also some very goad properties, such as biocompatibility and degradability. Crosslinking of degradable polymer based on the poly(ether-ester) DXO was performed with crosslinkers having the same reactivity as the monomer. 2,2-Bis(epsilon-caprolactone-4-yl)propane (BCP) and bis(epsilon-caprolactone-4-yl) (BCY) with tetrafunctionalities were synthesized from the corresponding diols and then used as comonomers during the polymerization of DXO. The comonomers showed the same reactivity to the initiator, stanneous 2-ethylhexanoic acid, as DXO and perfectly random crosslinked films were obtained. The crosslinked films showed a high degree of swelling already at 2-3 mol % BCP or BCY. The BCP crosslinker was somewhat less soluble in DXO at lower temperatures, but all BCP was soluble at 180 degrees C. These polymeric films were elastic with no crystallinity and the T-g values increased from -39 degrees C for pure DXO to -35 degrees C for BCP crosslinked films and -21 degrees C for BCY crosslinked ones.