2,4-Dinitrobenzenesulfonic acid in an efficient Bronsted acid-catalyzed controlled/living ring-opening polymerization of ε-caprolactone

The ring-opening polymerization of epsilon-caprolactone (epsilon-CL) using benzyl alcohol (BnOH) as initiator and 2,4-dinitrobenzenesulfonic acid (DNBA) as catalyst in acetonitrile at room temperature with a [epsilon-CL](0)/[BnOH](0)/[DNBA](0) ratio of 40/1/1 has been investigated. The polymerization proceeded to obtain poly(epsilon-caprolactone) (PCL) with controlled molecular weights. In addition, H-1 NMR, SEC, and MALDI-ToF MS measurements demonstrated the initiator residue at the polymer chain end. Furthermore, propargyl alcohol, 5-hexen-1-ol, 2-hydroxyethyl methacrylate, 1,epsilon-propanediol, and pentaerythritol were used as functional initiators to successfully obtain end-functionalized and alpha,omega-dihydroxy telechelic polyesters. The block copolymerization of PCL and PVL or PTMC provided conditions to afford well-defined poly(epsilon-caprolactone)-block-poly( delta-valerolactone) (PCL-b-PVL) and poly(epsilon-caprolactone)-block-poly(trimethylene carbonate) (PCL-b-PTMC).