NETWORKS AND GELS OF STIFF ZIGZAG POLYAMIDES

Two series of stiff zigzag polyamide network gels were prepared from monomers in solution by one-step polymerization. Within each, all stiff segments are of identical length, l = 19 angstrom and l = 32 angstrom, respectively. The bends between segments are rigid and of 120-degrees. The distances between branchpoints, l0, are average ones and were controlled by the appropriate monomer mix in the reaction bath. In general, the series with l = 19 angstrom produced networks with low defect concentration and the series with l = 32 angstrom was characterized by rather highly defective networks. Upon equilibrium in DMAc, the 19-angstrom zigzag series exhibited shear moduli, G, very close to those of rigid rodlike network gels of comparable concentrations and 1 or 2 orders of magnitude larger than comparable gels of flexible chains. The power dependence of the modulus on the equilibrium concentration and on l0 is intermediate between that observed for rigid rodlike network gels and that theoretically expected from swollen flexible chain networks. The more defective series, with l = 32 angstrom, showed huge drops in G with small decreases in the concentration, reflecting their defective nature. Their moduli do not follow power law dependence on either l0 or the concentration. In the poor solvent formamide, both series shrink and undergo microsyneresis. The results in poor solvent are, hence, given but are not discussed.