Recent advances in ring-opening polymerization strategies toward α,ω-hydroxy telechelic polyesters and resulting copolymers

Abstract

α,ω-Hydroxy telechelic polymers, namely macromolecules with reactive hydroxyl end-groups at each chain-end, are industrially highly valuable as building blocks for various ABA or multiblock copolymer architectures. This feature article reviews the different synthetic strategies that we have been developing over the past decade for the preparation of α,ω-hydroxy telechelic polyesters. The ring-opening polymerization (ROP) of several cyclic esters and carbonate, namely ε-caprolactone (CL), β-butyrolactone (BL) or trimethylene carbonate (TMC), catalyzed by intrinsically different systems based on discrete group III metal borohydride complexes, zinc alkoxide compounds generated in situ, metallic salts or organocatalysts, directly affords the corresponding difunctionalized hydroxy telechelic poly(ε-caprolactone) (PCL), poly(3-hydroxybutyrate) (PHB) or poly(trimethylene carbonate) (PTMC), PCL–(OH)2, PHB–(OH)2 or PTMC–(OH)2, respectively. Subsequent use of such macro-diols in the polymerization of a co-monomer allows the preparation of unique triblock polyester copolymers. The post-polymerization chemical modification of di-OH functionalized PCLs into the corresponding di-NH2 or di-Br polymers, followed by the ROP of γ-benzyl-l-glutamate N-carboxyanhydride (BLG), or by the radical polymerization of methyl methacrylate (MMA), enables to access to PCL–PBLG2 (PBLG: poly(γ-benzyl-l-glutamate N-carboxyanhydride)) and PCL–PMMA2 (PMMA: poly(methyl methacrylate)) triblock copolymers, respectively. Finally, polyaddition of a diamine with the di-(cyclocarbonate) end-functionalized PTMC, derived from PTMC diols, smoothly affords non-isocyanate polyurethanes (NIPUs). The quite different opportunities within reach from α,ω-hydroxy telechelic polyesters, that we have successfully explored, are thus highlighted.