Abstract
Vinyltrimethoxysilane (VTMS), methyltrimethoxysilane (MTMS) and tetramethylorthosilicate (TMOS) were mixed in a one-step basic catalyzed sol–gel chemistry, to produce flexible and good thermal insulator silica-based aerogels. Moreover, mechanical reinforcement of the aerogels with a polymer phase was accomplished via free radical polymerization using either the macromer poly(ethylene glycol) diacrylate (PEG-DA) or the monomer 2-(dimethylamino)ethyl methacrylate (DMAEMA), the latter case resulting in the grafting of PDMAEMA. Both the influence of using a monomer or a macromer and of applying two different polymer grafting approaches—one-pot synthesis or gel soaking—on the aerogels’ final properties were analyzed. It was concluded that gel soaking strongly limits the diffusion of the organic moieties, creating heterogeneous materials. This approach led to denser and less hydrophobic aerogels with worse mechanical properties. The incorporation of low amounts of polymer with one-pot synthesis led to an improvement in the aerogels properties, making them less dense, more flexible and better insulators. The one-pot method also allowed to obtain aerogels with a very well-defined microstructure, due to the porogen role of the polymer, hence generating homogenous materials. It was found that the major differences in the aerogels properties occurred with different grafting approaches and not with different polymer phases, and the molecular weight of the organic moieties was not determinant for the materials homogeneity, in the studied cases. The obtained bulk densities ranged from 122 to 181 kg m−3, the thermal conductivity from 0.050 to 0.072 W m−1 K−1 and the modulus achieved 327 kPa. The addition of DMAEMA generated the best results when using the one-pot approach, providing the lightest and uncommonly flexible thermal insulator aerogels (modulus of ~70 kPa).
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Gurav JL, Jung I-K, Park H-H, Kang ES, Nadargi DY (2010) Silica aerogel: synthesis and applications. J Nanomater 2010:1–11. doi:10.1155/2010/409310
Aegerter MA (2011) Aerogels handbook. In: Advances in sol-gel derived materials and technologies. Springer. doi:10.1007/978-1-4419-7589-8
Durães L, Ochoa M, Rocha N, Patrício R, Duarte N, Redondo V, Portugal A (2012) Effect of the drying conditions on the microstructure of silica based xerogels and aerogels. J Nanosci Nanotechnol 12(8):6828–6834. doi:10.1166/jnn.2012.4560
Soleimani Dorcheh A, Abbasi MH (2008) Silica aerogel; synthesis, properties and characterization. J Mater Process Technol 199(1–3):10–26. doi:10.1016/j.jmatprotec.2007.10.060
Cai JY, Lucas S, Wang LJ, Cao Y (2011) Insulation properties of the monolithic and flexible aerogels prepared at ambient pressure. Adv Mater Res 391–392:116–120. doi:10.4028/www.scientific.net/AMR.391-392.116
Ochoa M, Durães L, Beja A, Portugal A (2012) Study of the suitability of silica based xerogels synthesized using ethyltrimethoxysilane and/or methyltrimethoxysilane precursors for aerospace applications. J Sol-Gel Sci Technol 61(1):151–160. doi:10.1007/s10971-011-2604-7
Randall JP, Meador MA, Jana SC (2011) Tailoring mechanical properties of aerogels for aerospace applications. ACS Appl Mater Interfaces 3(3):613–626. doi:10.1021/am200007n
Maleki H, Durães L, Portugal A (2014) An overview on silica aerogels synthesis and different mechanical reinforcing strategies. J Non-Cryst Solids 385:55–74. doi:10.1016/j.jnoncrysol.2013.10.017
Nguyen BN, Meador MA, Tousley ME, Shonkwiler B, McCorkle L, Scheiman DA, Palczer A (2009) Tailoring elastic properties of silica aerogels cross-linked with polystyrene. ACS Appl Mater Interfaces 1(3):621–630. doi:10.1021/am8001617
Guo H, Nguyen BN, McCorkle LS, Shonkwiler B, Meador MAB (2009) Elastic low density aerogels derived from bis[3-(triethoxysilyl)propyl]disulfide, tetramethylorthosilicate and vinyltrimethoxysilane via a two-step process. J Mater Chem 19(47):9054. doi:10.1039/b916355g
Maleki H, Durães L, Portugal A (2014) Synthesis of lightweight polymer-reinforced silica aerogels with improved mechanical and thermal insulation properties for space applications. Microporous Mesoporous Mater 197:116–129. doi:10.1016/j.micromeso.2014.06.003
Mulik S, Sotiriou-Leventis C, Churu G, Lu H, Leventis N (2008) Cross-linking 3D assemblies of nanoparticles into mechanically strong aerogels by surface-initiated free-radical polymerization. Chem Mater 20:5035–5046
Nguyen BC, Meador MA, Medoro A, Arendt V, Randall J, McCorkle L, Shonkwiler B (2010) Elastic behavior of methyltrimethoxysilane based aerogels reinforced with tri-isocyanate. ACS Appl Mater Interfaces 2(5):1430–1443. doi:10.1021/am100081a
Meador MA, Weber AS, Hindi A, Naumenko M, McCorkle L, Quade D, Vivod SL, Gould GL, White S, Deshpande K (2009) Structure-property relationships in porous 3D nanostructures: epoxy-cross-linked silica aerogels produced using ethanol as the solvent. ACS Appl Mater Interfaces 1(4):894–906. doi:10.1021/am900014z
Meador MAB, Scherzer CM, Vivod SL, Quade D, Nguyen BN (2010) Epoxy reinforced aerogels made using a streamlined process. ACS Appl Mater Interfaces 2(7):2162–2168. doi:10.1021/am100422x
Maleki H, Durães L, Portugal A (2015) Synthesis of mechanically reinforced silica aerogels via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization. J Mater Chem A 3(4):1594–1600. doi:10.1039/c4ta05618c
Vareda J (2015) Smart polymer reinforced silica based aerogels. MSc Thesis, Universidade de Coimbra
Durães L, Maia A, Portugal A (2015) Effect of additives on the properties of silica based aerogels synthesized from methyltrimethoxysilane (MTMS). J Supercrit Fluids 106:85–92. doi:10.1016/j.supflu.2015.06.020
He Y-L, Xie T (2015) Advances of thermal conductivity models of nanoscale silica aerogel insulation material. Appl Therm Eng 81:28–50. doi:10.1016/j.applthermaleng.2015.02.013
Durães L, Matias T, Patrício R, Portugal A (2013) Silica based aerogel-like materials obtained by quick microwave drying. Mater Werkst 44(5):380–385. doi:10.1002/mawe.201300140
Al-Oweini R, El-Rassy H (2009) Synthesis and characterization by FTIR spectroscopy of silica aerogels prepared using several Si(OR)4 and R′′Si(OR′)3 precursors. J Mol Struct 919(1–3):140–145. doi:10.1016/j.molstruc.2008.08.025
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This work was funded by FEDER funds through the Operational Programme for Competitiveness Factors—COMPETE and National Funds, through FCT—Foundation for Science and Technology under the project PTDC/EQU–EPR/099998/2008—GelSpace—Silica-Based Aerogels for Insulation of Spatial Devices.
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Vareda, J.P., Matias, T., Fonseca, A.C. et al. Flexible acrylate-grafted silica aerogels for insulation purposes: comparison of reinforcement strategies. J Sol-Gel Sci Technol 80, 306–317 (2016). https://doi.org/10.1007/s10971-016-4137-6
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DOI: https://doi.org/10.1007/s10971-016-4137-6