Combination of ring-opening polymerization and "click" chemistry for the synthesis of an amphiphilic tadpole-shaped poly(ε-caprolactone) grafted by PEO

A tadpole shaped poly(epsilon-caprolactone) (PCL; M-n = 24 500) was made amphiphilic by grafting the two PCL tails with PEO. In the first step, a macrocyclic PCL was synthesized by ring-opening polymerization of epsilon-caprolactone (epsilon CL) initiated by a cyclic tin(IV) dialkoxide and stabilized by local intramolecular photo-cross-linking. In the second step, the polymerization of a mixture of epsilon CL and alpha-chloro-epsilon-caprolactone (alpha Cl epsilon CL) was resumed with formation of two activated chloride containing PCL tails. In the third step, the chlorides were converted into azides onto which alkynyl end-capped PEO was grafted by the copper-mediated Huisgen's cycloaddition [3 + 2], thus giving a "click" reaction. The thermal properties of the final copolymer and the precursors were analyzed by differential scanning calorimetry. The amphiphilicity of the final copolymer was confirmed by micellization in water.