Photocrosslinking of functionalized rubber .6. Cationic polymerization of epoxidized rubber

Epoxidised natural rubber has been crosslinked quasi-instantly by UV-irradiation in the presence of a sulfonium salt. The ring-opening cationic polymerisation has been studied quantitatively by infrared spectroscopy and shown to proceed by long kinetic chains. A tridimensional dual polymer network has been produced by photocrosslinking of a rubber having both epoxy and pendent acrylate functions in its chain. The addition to the epoxidised rubber of a multifunctional monomer, such as vinyl ether, acrylate or cycloepoxide, leads to a substantial increase of the polymerisation rate, as well as of the degree of crosslinking. Interpenetrating polymer networks have thus been produced within a few tenths of a second under intense illumination, or within a few minutes by simple exposure to sunlight. The addition of a radical photoinitiator was shown to enhance the crosslinking polymerisation of the acrylate monomer, and at the same time to slow down that of the oxirane ring, because of mobility restrictions brought upon by the fast build up of the acrylate polymer network. Copyright (C) 1996 Elsevier Science Ltd