Interfractal Porosity in Gels of Rigid Aromatic Polyamide Networks and its Consequences

Abstract

Gels of rigid aromatic polyamide networks arc brittle in nature. They may be prepared in a single step from monomers. or from precursor fractal polymers (FPs) purified from monomers, dimers and higher oligomers. The relationship between the concentration at which the network gels are prepared and the size and number of interfractal voids is discussed. The modulus of gels prepared exclusively from FPs was found in an earlier work to show an inverse power dependence on the size of the precursor FPs.It is suggested here that. in a fashion similar to yet not identical with ceramics and other polycrystalline materials. the dependency may be associated with the number and size of interfractal flaws surpassing a critical size for the initiation and propagation of flaw-initiated cracks. At present we cannot exclude total porosity from consideration, but flaws much smaller than whole FPs appear t o be ineffective in crack initiation and catastrophic propagation.