A process for producing an aerogel or xerogel, which comprises reacting the following components and in the presence of a solvent and of at least one catalyst, with the reaction being carried out in the absence of water: at least one polyfunctional isocyanate, and at least one polyfunctional substituted aromatic amine (a2-s) having the general formula I where R 1 and R 2 can be identical or different and are each selected independently from among hydrogen and linear or branched alkyl groups having from 1 to 6 carbon atoms and all substituents Q 1 to Q 5 and Q 1' to Q 5' are identical or different and are each selected independently from among hydrogen, a primary amino group and a linear or branched alkyl group having from 1 to 12 carbon atoms, where the alkyl group can bear further functional groups, with the proviso that - the compound having the general formula I comprises at least two primary amino groups, where at least one of Q 1, Q 3 and Q 5 is a primary amino group and at least one of Q 1', Q 3' and Q 5' is a primary amino group, and - Q 2, Q 4, Q 2' and Q 4' are selected so that the compound having the general formula I has at least one linear or branched alkyl group, which can bear further functional groups, having from 1 to 12 carbon atoms in the α position relative to at least one primary amino group bound to the aromatic ring, and optionally at least one further polyfunctional aromatic amine (a2-u) which differs from the amines (a2-s) having the general formula I. at least one polyfunctional isocyanate, and at least one polyfunctional substituted aromatic amine (a2-s) having the general formula I where R 1 and R 2 can be identical or different and are each selected independently from among hydrogen and linear or branched alkyl groups having from 1 to 6 carbon atoms and all substituents Q 1 to Q 5 and Q 1' to Q 5' are identical or different and are each selected independently from among hydrogen, a primary amino group and a linear or branched alkyl group having from 1 to 12 carbon atoms, where the alkyl group can bear further functional groups, with the proviso that - the compound having the general formula I comprises at least two primary amino groups, where at least one of Q 1, Q 3 and Q 5 is a primary amino group and at least one of Q 1', Q 3' and Q 5' is a primary amino group, and - Q 2, Q 4, Q 2' and Q 4' are selected so that the compound having the general formula I has at least one linear or branched alkyl group, which can bear further functional groups, having from 1 to 12 carbon atoms in the α position relative to at least one primary amino group bound to the aromatic ring, and optionally at least one further polyfunctional aromatic amine (a2-u) which differs from the amines (a2-s) having the general formula I. - the compound having the general formula I comprises at least two primary amino groups, where at least one of Q 1, Q 3 and Q 5 is a primary amino group and at least one of Q 1', Q 3' and Q 5' is a primary amino group, and - Q 2, Q 4, Q 2' and Q 4' are selected so that the compound having the general formula I has at least one linear or branched alkyl group, which can bear further functional groups, having from 1 to 12 carbon atoms in the α position relative to at least one primary amino group bound to the aromatic ring, and