Key Words:UNCHARGED AUXILIARY BASES; N-HETEROCYCLIC CARBENES; ORGANOCATALYSTS; LACTIDE; POLYAMINOPHOSPHAZENES; CHALLENGES
Abstract:A new polystyrene supported cyclic trimeric phosphazene base (PS-CTPB) was designed and synthesized. It was demonstrated that hypotoxic poly (epsilon-caprolactone) (PCL) can be directly prepared via ring-opening polymerization (ROP) by using PS-CTPB as catalyst. The PS-CTPB catalyst was prepared via immobilization of cyclic trimeric phosphazene base (CTPB) moiety on polystyrene microspheres to obtain a heterogeneous organocatalyst. The composition and chemical structure of the heterogeneous PS-CTPB was systematically characterized using solid-state C-13 and P-31 MAS NMR, FTIR, SEM and element analysis. It was found that immobilization of CTPB on PS microsphere maintained its excellent catalytic activity for ROP of epsilon-CL, delta-valerolactone (delta-VL), raclactide (rac-LA). Moreover, the heterogeneous PS-CTPB could be easily separated or recycled via simple filtration. Given that, the obtained polyesters contained negligible catalyst residual, so the obtained PCL samples have low cytotoxicity indicated from MTT assay. It was worth noting that the recycled PS-CTPB catalyst could be reused for another six consecutive cycles without significant decrease of catalytic activity.
Volume:204
Translation or Not:no