The invention relates to a porous material comprising at least one polyfunctional isocyanate (a1) and at least one polyfunctional substituted aromatic amine (a2-s) of the general formula (I): where R1 and R2 are selected from among hydrogen and linear or branched alkyl groups having from 1 to 6 carbon atoms and all substituents Q1 to Q5 and Q1′ to Q5′ are selected from among hydrogen, a primary amino group and a linear or branched alkyl group having from 1 to 12 carbon atoms, where at least one of Q1, Q3 and Q5 and at least one of Q1′, Q3′ and Q5′ is a primary amino group and the compound has at least one linear or branched alkyl group having from 1 to 12 carbon atoms in the α position relative to at least one primary amino group bound to the aromatic ring in formula (I).