CATIONIC EQUILIBRIUM RING-OPENING POLYMERIZATION OF BICYCLIC MONOMERSAND ITS APPLICATION TO CHEMICAL RECYCLING

Spiro orthoesters give poly(cyclic orthoester)s by single ring-opening polymerization in the presence of acid catalysts, and this process un dergoes the equilibrium polymerization. We have applied the function o f equilibrium polymerization to chemical recycling of polymeric materi als. Crosslinked poly(cyclic orthoester)s, prepared by radical additio ns of poly(cyclic orthoester)s possessing exomethylene groups and dith iols, efficiently decrosslinked to bifunctional spiro orthoesters in t he presence of CF3CO2H in CH2Cl2. The dithiol-linked bifunctional spir o orthoester monomers, prepared by the radical additions of spiro orth oester possessing exomethylene group and dithiols, afforded the corres ponding crosslinked polymers in the presence of CF3CO2H as a catalyst in bulk. The decrosslinking of the obtained crosslinked polymer procee ded quantitatively to obtain the corresponding bifunctional monomer at room temperature in CH2Cl2. Further, an acid-catalyzed reversible cro sslinking-decrosslinking of a polymer having a spiro orthoester group in the side chain was carried out. The copolymer obtained by the radic al copolymerization of 2-methylene-1,4,6-trioxaspiro[4.6]undecane with acrylronitrile was treated with CF3CO2H at -10 degrees C in CH2Cl2 to afford the crosslinked polymer quantitatively. The crosslinked polyme r was then treated with CF3CO2H at room temperature at a low concentra tion in CH2Cl2 to recover the original polymer.