The formation of ultralow-density microcellular diane-formaldehyde gels and aerogels

Abstract

A diane–formaldehyde aerogel is synthesized via a new two-step approach consisting of the sol–gel polycondensation of diane and formaldehyde. The first stage affords individual polymethylol phenols; at the second stage, these are cured in an alkaline solution at 225°С via the introduction of an additional amount of formaldehyde. The diane–formaldehyde gel is isolated for the first time from the initial solution at a minimum possible concentration of gel formation of 1 mg/mL. The aerogel is obtained during supercritical drying of the diane–formaldehyde gel. The density of the ultralow-density microcellular aerogels reaches 10.9 mg/cm3, and their specific surface area amounts to 340–716 m2/g. The features, structures, and properties of the resulting diane–formaldehyde gels are studied.