Nonmigratory Poly(vinyl chloride)- block -polycaprolactone Plasticizers and Compatibilizers Prepared by Sequential RAFT and Ring-Opening Polymerization (RAFT-T-ROP)

Well-defined nonmigrating polymeric plasticizers, poly(vinyl chloride)- block -polycaprolactone (PVC- b -PCL), were synthesized by sequential reversible addition–fragmentation chain transfer (RAFT) polymerization and ring-opening polymerization (ROP) with 2-hydroxyethyl 2-(ethoxycarbonothioylthio)propanoate (HECP) as RAFT agent and incipient initiator for ROP of ε-caprolactone (CL, oxepan-2-one). Kinetic experiments demonstrated that HECP provided good control in RAFT polymerization of vinyl chloride (VC) with dispersity ( Đ ) ∼ 1.2 for 3400 < M n < 11000. Chain extension experiments with VC and vinyl acetate proved the high end-group fidelity of the macroRAFT agent formed. The hydroxy end-group of the PVC macroRAFT agent allowed its use as a ROP initiator in forming a series of PVC- b -PCL with different PCL block lengths by RAFT-T̵-ROP. Characterization by wide-angle X-ray diffraction (WAXD), polarized light microscopy (PLM), and differential scanning calorimetry (DSC) indicates that there is enhanced chain entanglement for PVC- b -PCL block copolymers when compared to PCL homopolymers in PVC blends, which accounts for PVC- b -PCL being able to provide permanent plasticization. The PVC- b -PCL copolymers are also effective as polymeric compatibilizers in PVC/PCL blends where they suppress the migration of PCL. PVC blends plasticized with PVC- b -PCL show similar or better ductility than PVC containing the archetypical PVC plasticizer dioctyl phthalate (DOP) for the same level of plasticizer. Most importantly, the PVC- b -PCL polymeric plasticizers are nonleaching and do not migrate under conditions where DOP is readily extractable.