A NOVEL-APPROACH FOR THE CHEMICAL RECYCLING OF POLYMERIC MATERIALS - EQUILIBRIUM POLYMERIZATION SYSTEM OF SPIRO ORTHOESTERS

Crosslinked poly(cyclic orthoester)s prepared by radical additions of poly(cyclic orthoester)s possessing exomethylene groups and dithiols e fficiently depolymerized to bifunctional spiro orthoesters in the pres ence of trifluoroacetic acid in dichloromethane. Furthermore, the dith iol-linked bifunctional spiro orthoester monomers prepared by the radi cal additions of spiro orthoester possessing exomethylene group and di thiols afforded the corresponding crosslinked polymers in the presence of trifluoroacetic acid as a catalyst in bulk condition. The quantita tive depolymerization of the obtained crosslinked polymer afforded the corresponding bifunctional monomer in dichloromethane at room tempera ture. Meanwhile, an acid-catalyzed reversible crosslinking-depolymeriz ation of a polymer having a spiro orthoester group in the side chain w as carried out. The copolymer obtained by the radical copolymerization of 2-methylene-1,4,6-trioxaspiro[4.6]undecane with acrylonitrile was treated with trifluoroacetic acid in dichloromethane at 10 degrees C t o afford the crosslinked polymer quantitatively. The crosslinked polym er was then treated with trifluoroacetic acid at a low concentration i n dichloromethane at room temperature to recover the original polymer.