Comparisonal studies of surface modification reaction using various silylating agents for silica aerogel
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ORIGINAL PAPER: NANO- AND MACROPOROUS MATERIALS (AEROGELS, X E R O G E L S , CR Y O G E L S , E T C. )
Comparisonal studies of surface modification reaction using various silylating agents for silica aerogel Ha-Yoon Nah1 Younghun Kim1 Taehee Kim1 Kyu-Yeon Lee1 Vinayak G. Parale1 Chang-Hyun Lim1,2 Ji-Yeon Seo2 Hyung-Ho Park1 ●
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Received: 23 June 2020 / Accepted: 20 August 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Surface modification is one of the important steps for synthesizing hydrophobic silica aerogels by ambient pressure drying in which silylating agent plays a vital role. Trimethylchlorosilane and many kinds of methoxysilanes like trimethylmethoxysilane, dimethyldimethoxysilane, and methyltrimethoxysilane have been used as the silylating agents. In this work, silylation effects were investigated with different molar ratios of silylating agent/n-hexane mixture. In addition, the mechanism of the silylation reaction is explained based on the molecular structures by considering the number of methoxy/ methyl groups. The silylation extent was characterized by using optical imaging, bulk density and porosity analyses, Fouriertransform infrared spectroscopy, scanning electron microscopy, and Brunauer-Emmett-Teller, Barrett-Joyner-Halenda, and contact angle measurements. It has been found that the methoxysilane-based silylating agents can be used as a replacement without producing the harmful hydrochloric acid and retaining the similar tendency to trimethylchlorosilane in surface modification. This research approach seeks to an alternative silylating agent by investigating the impact on the surface modification based on the molecular structural parameters and reaction mechanisms. Graphical Abstract
These authors contributed equally: Ha-Yoon Nah, Younghun Kim * Hyung-Ho Park [email protected] 1
Department of Materials Science and Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, South Korea
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Korea Institute of Ceramic Engineering and Technology, 101 Soho-ro, Jinju-si, Gyeongsangnam-do 52851, South Korea
Journal of Sol-Gel Science and Technology
Keywords
Sodium silicate Silica aerogel Surface modification Trimethylchlorosilane Methoxysilane ●
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Highlights Sodium silicate-based silica aerogels were formed by using various silylating agents. ● Silylation ability depends on the molecular structure of the methoxysilane. ● Silylation could be evaluated from pore structure and electron distribution degree. ● DMDMS was found to be excellent silylating agent among the methoxysilanes studied. ●
1 Introduction Silica aerogels are known for nanomaterial due to its small pore diameter (~10 nm), high porosity (≥90%), and low thermal conductivity (~0.02 W/m·K) [1–4]. Various drying methods can be used to synthesize silica aerogels, such as supercritical drying (SCD), freeze drying (FD), and ambient pressure drying (APD), followed by a sol-gel process [1, 2]. In particular, APD is an attractive drying me
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