Regular network polyamide films made from trimesic acid (Y) and aliphatic diamines as well as copolyamide films made from hexamethylene diamine (6) and dodecamethylene diamine (12) with Y were prepared. Prepolymers obtained by melt polycondensation for a short period of time were cast from a DMF solution and successively post-polymerized at 300-degrees-C to form a network. The resultant films were transparent, flexible and insoluble in any solvents. Heat distortion temperature (T(h)) measured by a penetration mode of thermomechanical analysis rapidly increased with increasing post-polymerization time, and then levelled out after 0.5-1 h. T(h) was 238, 231, 232, 216, 207, 187, 176 and 163-degrees-C for 4Y, 5Y, 6Y, 7Y, 8Y, 9Y, 10Y and 12Y post-polymerized for 4 h, respectively. Degrees of reaction estimated from the infrared absorbance of ester and methylene groups were 88 and 83% for 6Y and 12Y post-polymerized for 4 h, respectively. Two diffraction peaks appeared in the wide angle X-ray scattering (WAXS) pattern, suggesting some ordered structure owing to the regular networks. Density increased with increasing post-polymerization time and was 1.266, 1.236, 1.214, 1.175, 1.162, 1.145, 1.130 and 1.107 g/cm3 for 4Y, 5Y, 6Y, 7Y, 8Y, 9Y, 10Y and 12Y post-polymerized for 4 h, respectively. WAXS patterns of copolymer films of 12/6-Y suggested the continuous change of network structure with copolymer composition. It was found that comonomer disturbs the formation of ordered network structure, and decreases the packing of networks, thus decreasing density, T(h) and tensile properties, and increasing dye absorption of copolymer films. From the dye absorption behavior, it was suggested that these regular network films could be utilized as membranes for the separation of molecules by varying the chain length between crosslinked sites.
