Synthesis of CO 2 -Based PPCP-Si Macrodiol and Its Application as a Macromolecular Plasticizer for Polyvinyl Chloride

As a commonly used thermoplastic, PVC suffers from intrinsic stiffness and therefore requires plasticizers to facilitate processing. Conventional small-molecule plasticizers (e.g., DOP, DBP) tend to migrate out of PVC over time, whereas polymeric plasticizers have lower migration but often suffer from poor compatibility at higher loadings. To address these issues, a novel carbon-dioxide-based polymeric diol, PPCP-Si macrodiol is designed and synthesized via one-pot copolymerization of CO2, propylene oxide, phthalic anhydride, and hydroxyl-terminated polydimethylsiloxane, using a metal-free catalyst system comprising bis(triphenylphosphine)iminium chloride and triethylborane. The resulting PPCP-Si macrodiols have a tunable molecular weight from 4k to 10k (polydispersity index < 1.25) and its soft-to-hard segment ratio could be adjusted through reaction conditions. When utilized them as a plasticizer for PVC, PPCP-Si macrodiol demonstrates outstanding plasticization efficiency in all synthesized molecular weight range. At a loading of 10 parts per hundred resin of a 4k molecular weight PPCP-Si macrodiol, the elongation at break of PVC increased 22-fold and the glass transition temperature was halved. The plasticized PVC exhibits minimal migration, with less than 1.2% weight loss after 350 h of solvent exposure. Scanning electron microscopy confirmed good compatibility of PPCP-Si macrodiol with the PVC matrix. These results indicate that PPCP-Si macrodiol combines the advantages of both small-molecule and macromolecular plasticizers, delivering high plasticization efficacy and stability against migration even at high molecular weights, thus making it a promising candidate for improving PVC flexibility in industrial applications.