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

Abstract

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.

Fundamentals of reversible addition–fragmentation chain transfer (RAFT)

“…These are star polymers prepared by RAFT polymerization that impart long term, temperature independent, viscosity to fluids such as oils (Brzytwa & Johnson, 2011). A further example is the preparation of novel RAFT synthesized additives that enable production of flexible PVC that is free of migratory additives and plasticizers (Sun, Choi, Feng, Moad, & Thang, 2019;Sun et al, 2020).…”

Efficient internal plasticization of poly(vinyl chloride) via free radical copolymerization of vinyl chloride with an acrylate bearing a triazole phthalate mimic

“…Migration is determined by analyzing the amount of plasticizer that leaches out from the PVC sample into a liquid phase. The solvent n-hexane is commonly used as the extraction medium to test migration stability of plasticized PVC, as the solubility profile of n-hexane is similar to that of cooking oil [60,61].…”

Internal plasticization of poly(vinyl chloride) by grafting acrylate copolymers via copper‐mediated atom transfer radical polymerization

“…However, the preparation of monomer DEHT‐HA required four synthetic steps. Thang, Moad and Feng 31 prepared PVC‐ b ‐polycaprolactone (PCL) in a two‐step polymerization process using reversible addition−fragmentation chain transfer (RAFT) polymerization, followed by ring‐opening polymerization (ROP). T g values as low as − 35°C were achieved using 90 wt% of PCL.…”