Strong, Thermally Superinsulating Biopolymer–Silica Aerogel Hybrids by Cogelation of Silicic Acid with Pectin

Abstract

Silica aerogels are excellent thermal insulators, but their brittle nature has prevented widespread application. To overcome these mechanical limitations, silica-biopolymer hybrids are a promising alternative. A one-pot process to monolithic, superinsulating pectin-silica hybrid aerogels is presented. Their structural and physical properties can be tuned by adjusting the gelation pH and pectin concentration. Hybrid aerogels made at pH 1.5 exhibit minimal dust release and vastly improved mechanical properties while remaining excellent thermal insulators. The change in the mechanical properties is directly linked to the observed "neck-free" nanoscale network structure with thicker struts. Such a design is superior to "neck-limited", classical inorganic aerogels. This new class of materials opens up new perspectives for novel silica-biopolymer nanocomposite aerogels.

Synthesis and biomedical applications of aerogels: Possibilities and challenges

“…The NFC scaffold improved the mechanical properties of silica aerogels and resulted in interpenetrating hybrid aerogel networks having low density (0.12-0.14 g/cm 3 ), high porosity (>93%) and high specific surface area (450 m 2 /g). In addition, the same research group has synthesized strong aerogels based on silica-pectin hybrid matrices, in which the pectin was incorporated in the silica network through a controlled parameter one-pot synthesis approach [177].…”

Polyethylene Aerogels with Combined Physical and Chemical Crosslinking: Improved Mechanical Resilience and Shape‐Memory Properties

“…[7] This step is particularly important so as to prevent collapse of the pores if they are only af ew nanometers in size,orifthe solid network is not rigid enough. [11] Another class of organic aerogels comprises high-molar-mass semicrystalline polymers.S uch materials are obtained from entangled dilute solutions that undergo physical gelation upon crystallization of polymer segments.Alarge variety of hydrophilic polymer based aerogels,o ften derived from biomass,h as been studied over the years. Thus,t hey lead to aerogels with lower surface areas,i nt he range 10-500 m 2 g À1 ,a nd with at endencyt oh ave al arger and hierarchical distribution of pore sizes,typically mesopores in the 5-50 nm range,but also larger macropores over 50 nm.…”

Fire‐Retardant and Thermally Insulating Phenolic‐Silica Aerogels

“…[1] Decreasing heat transfer through better insulation is probably the most important factor to improve the energy efficiencyo f buildings and there is an eed to develop materials with asuperior insulation performance compared to commercially available polymeric insulation materials,s uch as expanded polystyrene (EPS) and inorganic insulating materials,such as glass wool. [5] However,addition of inorganic fillers to an organic material increases the density and can make the hybrid more fragile.Poor compatibility between the inorganic fillers and the polymer matrix can also result in catastrophic disintegration during combustion and fail to prevent thermally induced collapse of the building. [3] Unfortunately,m any of the commonly used flame retardants are halogenated or phosphorous compounds with potential impacts on the environment and human health, especially the brominated flame retardants which will generate neurotoxic and potentially carcinogenic brominated furans and dioxins.…”

“…[2] Thermally insulating materials also have to be fire retardant and mechanically resilient or flexible.P olymeric insulation materials are often flexible but easily ignitable and can sustain and rapidly spread af ire in the absence of fire barriers.The fire retardant properties of polymeric insulation materials,s uch as EPS,c an be improved by the addition of flame retardants. [5] However,addition of inorganic fillers to an organic material increases the density and can make the hybrid more fragile.Poor compatibility between the inorganic fillers and the polymer matrix can also result in catastrophic disintegration during combustion and fail to prevent thermally induced collapse of the building. [4] Recent work has shown that the flame retardant properties of organic-inorganic composites can be significantly improved by the addition of well-distributed inorganic fillers, such as carbon nanotubes,s ilica, layered montmorillonite (MMT), needle-like sepiolite and metal oxides or hydroxides (e.g.…”

“…[3] Unfortunately,m any of the commonly used flame retardants are halogenated or phosphorous compounds with potential impacts on the environment and human health, especially the brominated flame retardants which will generate neurotoxic and potentially carcinogenic brominated furans and dioxins. [5] However,addition of inorganic fillers to an organic material increases the density and can make the hybrid more fragile.Poor compatibility between the inorganic fillers and the polymer matrix can also result in catastrophic disintegration during combustion and fail to prevent thermally induced collapse of the building. MgO or LDHs).…”