Polymer-crosslinked aerogels are a class of nanocomposite materials in which a conformal polymer coating follows the contour surfaces of the aerogel's skeletal framework chemically connecting the elementary building blocks (e.g., nanoparticles) of its solid network and providing mechanical reinforcement to an otherwise fragile material. Herein by definition, "crosslinking" refers to the nanoscopic rather than the molecular level and is based on polymeric networks rather than molecular segments. The bulk density of polymer-crosslinked aerogels remains low relative to native aerogels, yet their mechanical properties (stiffness, ultimate compressive strength) improve dramatically (up to 300x), while their mass-normalized (specific) energy absorption capabilities can surpass those of armor-grade ceramics. Most polymer-crosslinked aerogels are based on underlying inorganic oxide native frameworks, yet the methodology is rapidly expanding to polymer-crosslinked polymer and biopolymer aerogels as well. This chapter comprises a comprehensive review of the synthesis, characterization, and applications of all types of polymer-crosslinked aerogels in the broader topological context of sol–gel nanocomposites. Emphasis is placed on the origin of strength in polymer-crosslinked aerogels in relation to the location of the polymer relative to the fractal nanostructure of the underlying skeletal framework, and we discuss how those insights have led to a paradigm shift in the design of mechanically durable aerogels and the accompanying rapid development of high-strength all-polymer aerogels over the past decade. Applications of polymer-crosslinked aerogels as strong lightweight multifunctional materials and as precursors for the synthesis of ceramic and metallic aerogels are also discussed.
N. Leventis et al., "Polymer-Crosslinked Aerogels," Springer Handbooks, pp. 749 - 790, Springer, Jan 2023.
The definitive version is available at https://doi.org/10.1007/978-3-030-27322-4_29
Keywords and Phrases
Aerogels; Ballistic protection; Composites; Conformal coating; Mechanical strength; Polymer; Polyurea; Silica aerogels
International Standard Serial Number (ISSN)
Article - Journal
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01 Jan 2023