Nanocomposite membranes consisting of poly(vinyl chloride) graft copolymer and surface-modified silica nanoparticles

A graft copolymer of poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM) was synthesized via atom transfer radical polymerization (ATRP), and fumed silica (SiO₂) nanoparticles were modified by grafting POEM via a three-step synthetic approach. The resultant graft copolymer and modified SiO₂ nanoparticles were solution blended to prepare PVC-g-POEM/SiO₂-POEM nanocomposite membranes. Uniform distribution of SiO₂-POEM nanoparticles in the membranes and microphase-separated morphology were confirmed by transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). X-ray diffraction (XRD) analysis revealed increased randomness in the amorphous phase of PVC-g-POEM and continuous decrease in the interchain d-spacing with increased SiO₂-POEM content, indicating a more closely packed nanocomposite membrane structure. The mechanical properties of PVC-g-POEM/SiO₂-POEM membranes were superior to those of PVC-g-POEM, resulting from strong interfacial interactions in the membranes due to the segregation and entanglement of the POEM chains. In addition, the permeation performances of the PVC-g-POEM/SiO₂-POEM nanocomposite membranes were somewhat better than those of PVC-g-POEM, which showed excellent CO₂/N₂ and CO₂/H₂ separation capabilities. For example, the CO₂ permeability and CO₂/N₂ selectivity of PVC-g-POEM/SiO₂-POEM (2%) at 35 °C were 200 Barrer and 43, respectively. Thus, we successfully prepared membranes that deliver high permeation properties, as well as good mechanical properties. [Figure not available: see fulltext.]