Synthesis of degradable crosslinked polymers based on 1,5-dioxepan-2-one and crosslinker of bis-ϵ-caprolactone type

Poly(lactones) may be crosslinked by ring-opening polymerization of the corresponding cyclic esters in the presence of tetrafunctional bis(ϵ-caprolactone). The homopolymer of 1.5-dioxepan-2-one (DXO) has poor mechanical properties but also some very good 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(ϵ-caprolactone-4-yl)propane (BCP) and bis(ϵ-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°C. These polymeric films were elastic with no crystallinity and the T_g values increased from −39°C for pure DXO to −35°C for BCP crosslinked films and −21°C for BCY crosslinked ones. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1635–1649, 1997