Abstract
Methods of X-ray analysis, IR spectroscopy and thermomechanical analysis have been used to investigate the structure of oriented polyamidoimides (PAI) and polyester amidoimides (PEAI) differing as to the structure of the diamine fragments. It is shown that heat treatment of polyamidoacid films with 150–250% elongation is accompanied by a marked change in the dichroism of absorption bands in the temperature interval 270–300° for polymers having phenylene in the meta-position. In this case it appears from the X-ray data that a highly oriented crystalline or mesomorphic structure is formed. Crystallographic parameters were determined for the ordered structures and conformational structures for the PAI and PEAI are proposed. For PAI containing the p-phenylene unit in the diamine the energetically most favourable packing of chains in the crystal lattice was calculated on the basis of atom-atom potentials.
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