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Issue 18, 2012
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Role of block copolymer surfactant on the pore formation in methylsilsesquioxane aerogel systems

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Abstract

Transparent and low-density methylsilsesquioxane (MSQ, CH3SiO1.5) aerogels can be obtained solely from methyltrimethoxysilane (MTMS) by a one-pot two-step process under the co-presence of surfactant. In the present study, we have systematically investigated the effects of the molecular structure of triblock copolymer-type nonionic surfactants PEO-b-PPO-b-PEO (PEO and PPO denote poly(ethylene oxide) and poly(propylene oxide) units, respectively) on the properties of the resultant MSQ aerogels. Macroscopic phase separation of hydrophobic MSQ networks from polar solvent occurs when no surfactant is employed, which results in macroporous opaque aerogels. In contrast, a co-presence of appropriate surfactant effectively suppresses the phase separation and yields transparent aerogels after supercritical drying. By employing various surfactants having different molecular weight and PO/EO ratio, the mechanism of suppression of phase separation or pore formation is discussed in detail. In situ1H NMR suggests that the PO units of surfactant interact with the hydrophobic MSQ network enriched with methyl groups and make the MSQ network hydrophilic by extending EO chains toward the aqueous solvent in the late phase of gelation, until which hydrogen bonding dominates between the Si-OH groups of polymerizing MSQ and the ether oxygens of the EO unit. Through the comprehensive understanding of the role of surfactant, the strategy for rational design of MSQ aerogels materials has become developable.

Graphical abstract: Role of block copolymer surfactant on the pore formation in methylsilsesquioxane aerogel systems

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Publication details

The article was received on 27 Apr 2012, accepted on 31 May 2012 and first published on 09 Jul 2012


Article type: Paper
DOI: 10.1039/C2RA20799K
Citation: RSC Adv., 2012,2, 7166-7173
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    Role of block copolymer surfactant on the pore formation in methylsilsesquioxane aerogel systems

    M. Kurahashi, K. Kanamori, K. Takeda, H. Kaji and K. Nakanishi, RSC Adv., 2012, 2, 7166
    DOI: 10.1039/C2RA20799K

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