Synthesis of temperature-responsive magnetic mesoporous silica and temperature dependence of its physical properties

Abstract

In this study, a novel composite (PAMMS) was prepared using poly (N-isopropylacrylamide) (PNIPAM) as a temperature-responsive polymer, magnetite as a magnetic substance, and amino-functionalized mesoporous silica (MS) as an adsorbent. The temperature-dependence of the physical properties such as methyl orange (MO) adsorption, aggregation/sedimentation, and magnetic separation of this composite was investigated. It was found that the composite consisted of 11.3 wt% magnetite, 0.6 mmol/g amino groups, and 4.6 wt% PNIPAM. The MO adsorption behaviour of the PAMMS composite could be well-explained by the Langmuir model and pseudo-second-order rate equation. At 20 °C (below the lower critical solution temperature (LCST) of PNIPAM), the composite showed an MO adsorption amount of 174 μmol/g, which is slightly larger than that (143 μmol/g) at observed 35 °C (above the LCST of PNIPAM). The optical microscopic observations revealed that the size of the PAMMS aggregates at 45 °C (above LCST) was larger than that at room temperature. Hence, the magnetic separation ratio of PAMMS at 45 °C was higher than that at room temperature. The PAMMS composite showed effective MO adsorption below the LCST of PNIPAM and magnetic separation above the LCST of PNIPAM.