Poly (N-Vinyl caprolactam), a thermal responsive support with tunable phase transition temperature for catalyst

Abstract

Titanium dioxide (TiO2) nanoparticle is one of the most widely used photocatalyst and adsorbent. Post treatment removal of the nanoparticle is an expensive and difficult task. Poly N-vinyl caprolactam (PNVCL) undergo phase transition at molecular weight dependent temperature. Up to now immobilize TiO2 nanoparticle with PNVCL via controlled radical polymerization has not been reported. In this work, surface initiate RAFT polymerization of PNVCL is investigated. Benzyl sulfanyl thio carbonyl sulfanyl propionic acid (BPA) was used as chain transfer agent and covalently bonded to the nanoparticle. The obtained TiO2-PNVCL was tested for photocatalysis and metal ion adsorption. Results indicated that molecular weight distribution of PNVCL was narrowed down to 1.37 in the presence of BPA; LCST of PNVCL was tuned from 36 to 41 °C; RAFT polymerization of PNVCL was successfully initiated from TiO2 surface; the graft percentage was controlled by change feed ratio. TiO2-PNVCL suspension was stable at atmospheric temperture, and precipitated in 10 s upon heating. TiO2-PNVCL showed high adsorption capacity to Mn2+ (16.4 mg/g) and Cr6+ (9.7 mg/g) ions. Photocatalytic activity of TiO2-PNVCL was switchable by changing temperature; the degradation of Rhodamine B was 68.0% at 25 °C and 7.7% at 40 °C in 3 h period.