Carbon Aerogels from Furan-Based Polybenzoxazine Precursors

Polymer aerogels typically have physical properties that consist of high internal surface area (500-850m²/g), nano-scale pore size (10-30 nm), and high porosity (>97%), which lend to very low density and thermal conductivities. It is possible to enhance these materials by manipulating the chemistry of the underlying matrix. Polybenzoxazines are a thermosetting polymer that have low water retention, near zero volume shrinkage during cure, and high glass transition temperature making them ideal candidates to comprise the network of a polymer aerogel. When furan is introduced into the chemical structure, polybenzoxazines have been shown to have char yields exceeding 60% further expanding their use as the precursor network in carbon aerogels. Carbon aerogels have found applications in energy storage, adsorbents, and as thermal insulators due to their high electrical conductivity, chemical resistance, and the ability to withstand extreme temperatures of up to 3000 ℃ before degradation. In this study, a monofunctional furan-based benzoxazine with 4-hydroxybenzyl alcohol as the phenolic derivative and a difunctional furan-based benzoxazine with bisphenol A as the phenolic derivative was synthesized. Each monomer was thermally gelled at 140 ℃. Monomer weight concentration in dimethyl formamide (DMF) and its effect on volume shrinkage, surface area, and thermal stability with respect to the different furan-based polybenzoxazine chemistries was investigated. Carbon aerogels were fabricated from pyrolysis in a nitrogen atmosphere up to 1000 ℃ with a ramp rate of 10 ℃ min^-1. The findings from this study provide a framework for the fabrication of carbon aerogels from furan-based polybenzoxazine precursors.