Branching Structured Poly(vinyl chloride-co-hydroxyethyl acrylate)-g-polycaprolactone as Nonmigratory Polymeric Plasticizers and Compatibilizers in Flexible PVC

In this work, a series of nonmigrating polymeric plasticizers with a branched structure, poly(vinyl chloride-co-hydroxyethyl acrylate)-g-polycaprolactone (PVC-co-PHEA-g-PCL), were fabricated by the sequential precipitation copolymerization and ring-opening polymerization (ROP). Initially, the precipitation copolymerization of vinyl chloride monomer with hydroxyethyl acrylate was conducted in a nonaqueous reaction medium by controlling the monomer feed ratio via semibatch to synthesize poly(vinyl chloride-co-hydroxyethyl acrylate) (PVC-co-PHEA) copolymers. The gel permeation chromatography and nuclear magnetic resonance spectroscopy (H NMR) demonstrated that the synthesized PVC-co-PHEA copolymers had low number-average molecular weight (Mn, 8000–12,000 g/mol) and possessed uniform polymer composition (wHEA = 2.9%, 7.0%, and 12.0%). Subsequently, utilizing the hydroxy side-group of the PVC-co-PHEA copolymer as the incipient macroinitiator for the ROP of ε-caprolactone to form a series of PVC-co-PHEA-g-PCLs with different grafting densities and side-chain lengths. Characterization by 1H NMR spectra, wide-angle X-ray diffraction, dynamic mechanical analysis, and differential scanning calorimetry indicated the successful preparation of PVC-co-PHEA-g-PCLs with a branched structure and their suitability as permanent plasticizers in the PVC matrix. The enhancement in both the mechanical strength and superior migration resistance highly verified the strong chain entanglement between PVC-co-PHEA-g-PCLs with the PVC matrix in comparison to the pure dioctyl phthalate (DEHP) and PCL-3000. Moreover, these PVC-co-PHEA-g-PCLs also exhibited outstanding compatibility with the PVC matrix and resulted in the PVC blend with excellent transmittance.