Anklam Thomas, Tannert René
Institute for Materials Research, German Aerospace Center (DLR), Linder Höhe, 51147, Cologne, Germany.
Institute of Inorganic Chemistry, University of Cologne, Greinstrasse 4-6, 50939, Cologne, Germany.
Macromol Rapid Commun. 2025 Jan;46(2):e2400691. doi: 10.1002/marc.202400691. Epub 2024 Sep 30.
Phenolic aerogels based on resorcinol-formaldehyde (RF) are among the best thermally insulating materials. However, the hydrophilicity inherent to the free phenolic moiety of RF gels generally limits their actual range of applications. Prior efforts to render phenolic gels hydrophobic are restricted to post-synthetic functionalizations of hydrophilic gels, processes that are often limited in efficiency, scope, and/or longevity. Here, an acid-mediated conversion of 1,3,5-trimethoxybenzene with formaldehyde is reported, yielding monolithic trimethoxybenzene-formaldehyde (TMBF) aerogels and xerogels with low density (0.11-0.30 g cm), high porosity (74-92 %), inner surface areas (S) of up to 284 m g, and thermal conductivity of 34.5-43.9 mW m K. For a monolithic xerogel based on TMBF xerogels an unprecedently low thermal conductivity of 34.5 mW m K could be achieved. In addition, all TMBF gels are thermally stable (degradation >280-310 °C) and highly hydrophobic (water contact angles 130°-156°). As such, TMBF serves as a new class of inherently hydrophobic aerogels and xerogels and useful complement to RF materials.
基于间苯二酚-甲醛（RF）的酚醛气凝胶是最好的隔热材料之一。然而，RF凝胶中游离酚部分固有的亲水性通常限制了它们的实际应用范围。此前使酚醛凝胶疏水化的努力仅限于亲水性凝胶的合成后功能化，这些过程在效率、范围和/或寿命方面往往受到限制。在此，报道了一种酸介导的1,3,5-三甲氧基苯与甲醛的转化反应，生成了具有低密度（0.11 - 0.30 g/cm³）、高孔隙率（74 - 92%）、高达284 m²/g的内表面积（S）以及34.5 - 43.9 mW/(m·K)热导率的整体式三甲氧基苯-甲醛（TMBF）气凝胶和干凝胶。对于基于TMBF干凝胶的整体式干凝胶，可实现低至34.5 mW/(m·K)的热导率。此外，所有TMBF凝胶都具有热稳定性（降解温度>280 - 310°C）且高度疏水（水接触角为130° - 156°）。因此，TMBF作为一类新型的固有疏水气凝胶和干凝胶，是RF材料的有益补充。
