A Recoverable, Metal-Free Catalyst for the Green Polymerization of ε-Caprolactone

Abstract

n-Propylsulfonic acid-functionalized porous and nonporous silica materials are evaluated in the ring-opening polymerization of -caprolactone. All catalysts allow for the controlled polymerization of the monomer, producing polymers with controlled molecular weights and narrow polydispersities. Polymerization rates are low, with site-time yields generally 1-3 orders of magnitude lower than metalbased systems. The catalysts are easily recovered from the polymerization solution after use and are shown to contain significant residual adsorbed polymer. Solvent extraction techniques are useful for removing most of the polymer, although the extracted solids are not effective catalysts in recycle experiments under the conditions used here. These new materials represent a green alternative to traditional metal-based catalysts, as they are recoverable and leave no metal residues in the polymer.

Controlled ring‐opening polymerization of ε‐caprolactone using polymer‐supported scandium catalyst

“…Although some metal complexes might be grafted onto a silica or alumina support, 13,[20][21][22][23] the regeneration and recycle was unsuccessful. 20 From the perspective of green chemistry, further development of a recoverable polymer-supported catalyst is desired. As a recent synthesis of PCL, ROP of e-caprolactone catalyzed by enzyme is also investigated.…”

Heterogeneous ring‐opening polymerization of lactones for biomedical applications

“…In a separate study, the effect of porosity and structure of porous and nonporous silica supports on the reaction rate during ring‐opening polymerization of ε‐caprolactone was reported 59. The polymerization was carried out at 52 °C with sulfonic acid immobilized on silica supports and it was demonstrated that supported catalysts were less active than the homogeneous system presumably due to internal diffusion limitations inherent in porous solid catalysts.…”

Sulfonic acid catalyst based on silica foam supported copolymer for hydrolysis of cellulose

“…In this case, Cab-O-Sil M5, a nonporous silica, is used as the support to avoid potential pore clogging issues associated with polymerization with porous materials as the supports [18][19].…”