THERMAL FLEXIBILITY OF AROMATIC POLYAMIDE CHAINS IN SOLUTION FROM VISCOMETRIC ANALYSIS

Intrinsic viscosities of poly (p-phenylene terephthalamide) (PPTA) and poly (m-phenylene isophthalamide) (PMIA) samples of the same molecula r weight are determined in 90%, 96% and 100% sulfuric acid at temperat ures from 0 to 130-degrees-C. Conditions are established under which t he degree of coiling of PPTA molecule is close to that for PMIA. Exper imental data are compared with the results of theoretical calculations of the Kuhn segment length. In the light of this comparison, some qua ntitative characteristics of the deformational flexibility mechanism f or aromatic polyamide chains and the hindrance to intramolecular rotat ion are discussed.