Synthesis of copolymer CPPA-PCL (macro-CPPA) by ring opening polymerization

The copolymer CPPA–poly(ε-caprolactone) (PCL) (macro-CPPA) was synthesized by free-radical polymerization starting from the chain-transfer agent CPPA.21 In brief, CPPA (50 mg) was added into a three-necked round-bottom flask and the residual water and oxygen were removed by evacuating and purging with nitrogen for at least 1 hour. Toluene (20–30 mL), predried over calcium hydride, was then added. A given concentration of ε-caprolactone monomers (2.2 mL) was added until the reagent was dissolved in the solvent in the presence of Sn(Oct)₂ as a catalyst. The reaction was maintained at 130°C with continuous stirring for 48 hours under nitrogen. Macro-CPPA powders were precipitated with cold ethyl ether twice to remove unreacted ε-caprolactone monomers, and the remaining products were collected by vacuum filtration. The orange powder obtained was dried under vacuum at room temperature to evaporate the solvent. The details of the method are presented in Figure 2.

Synthesis of the copolymer p(NIPAAM-co-PEGMEA)-b-PCL.

Abbreviations: NIPAAM, N-isopropylacrylamide; PEGMEA, poly(ethylene glycol) methyl ether acrylate; PCL, poly(epsilon-caprolactone); RAFT, reversible addition-fragmentation chain transfer; CPPA, 4-cyano-4-(phenylcarbonothioylthio) pentanoic acid; THF, tetrahedrofuran; AIBN, azobisisobutyronitrile.