Synthesis of Mesoporous Silica with Different Morphologies for Application in Smart Window

Abstract

Mesoporous silica has many favorable properties including a high specific surface area a tunable pore size a low bulk density and a controllable morphology It is thus used in many applications nowadays Mesoporous silica is most commonly prepared using surface-activation or surfactant-templating methods In the present study mesoporous silica with a tunable pore size in the range of 2 5 to 5 0 nm and different morphologies were successfully prepared by using PMMA beads SiO2 beads and nano CaCO3 as hard templates gelatin and AEO-L67 as surface activation reagents and Tetraethyl orthosilicate (TEOS) and sodium silicate as silica sources Following silicification on the activated hard templates mesoporous silica with a hollow interior was obtained via calcination at 500°C or acid-washing to remove the hard template and surface activation reagent In addition pillar-within-sphere mesoporous silica with an MCM-41 structure was synthesized using cationic surfactant (C14TABr) and cosurfactant (butanol) as templates and sodium silicate as the silica source The pore size and surface properties of the mesoporous silica were tuned through a careful control of the reaction conditions (e g the acidification rate the hydrothermal temperature and the molar ratio of the surfactant mixture) The results showed that the synthesized mesoporous silica had a high surface area of ~1200 m2/g and a tunable pore size in the range of 2 0 to 3 0 nm The mesoporous silicas with different morphologies were hydrophobically modified with chlorotrimethylsilane and then dispersed in nematic liquid crystal to form smart windows The electro-optic characterization results showed that the addition of mesoporous silica with modified hydrophobic functional groups and sufficient pores enhanced the uniformity of the liquid crystal-silica mixture and improved the transparency of the liquid crystal under the application of an external driving field Moreover the mesoporous silica prolonged the transparency state of the smart window following the removal of the external voltage The resulting smart windows therefore have significant potential as a green building material

Date of Award	2020
Original language	English
Supervisor	Hong-Ping Lin (Supervisor)