Combining ATRP of methacrylates and ROP of L,L-dilactide and ε-caprolactone

Coupling atom transfer radical polymerization (ATRP) and coordination-insertion ring-opening polymerization (ROP) provided a controlled two-step access to polymethacrylate-graft-polyaliphatic ester graft copolymers. In the first step, copolymerization of methyl methacrylate (MMA) and 2-hydroxyethyl methacrylate (HEMA) was carried out at 80°C at high MMA concentration by using ethyl 2-bromoisobutyrate and [NiBr₂(PPh₃)₂] as initiator and catalyst, respectively. Kinetic and molar masses measurements, as well as ¹H NMR spectra analysis of the resultingpoly(MMA-co-HEMA)s highlighted the controlled character of the radical copolymerization, while the determination of the reactivity ratios attested preferential incorporation of HEMA. The second step consisted of the ROP of e-caprolactone or L,L-dilactide, in THF at 80°C, promoted by tin octoate (Sn(Oct)2) and coinitiated by poly(MMA-co-HEMA)s obtained in the first step. Once again, kinetic, molar mass, and ¹H NMR data demonstrated that the copolymerization was under control and started on the hydroxyl functions available on the poly(MMA-co-HEMA) multifunctional macroinitiator.