TY  - JOUR
A1  - Lavrenko, Peter N.
A1  - Okatova, Olga V.
A1  - Cherkasov, Victor A.
A1  - Schulz, Burkhard
T1  - Hydrodynamic properties of Poly(p-phenylene-oxadiazole) in various stages of hydrolytic thermal degradation in sulfuric acid
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Lavrenko, Peter N.
A1  - Okatova, Olga V.
A1  - Schulz, Burkhard
T1  - Hydrodynamic properties and conformation of the molecules of meta- and para-isomers of polyphenyleneoxadiazole in sulphuric acid
N2  - Translational diffusion of poly(1,4-phenylene-1,3,4-oxadiazole) in 96% H2S04 was studied, and the intrinsic viscosity of the polymer solution was measured in various stages of degradation at temperatures from 82 to 105°C. The rate constant of the degradation process was determined from variation of the molecular mass of the degradation products with time at a fixed solution temperature, and the activation energy of the process was calculated using the temperature dependence of the rate constant. The activation energy (E = 103 ± 7 kJ/mol) is lower than that for the hydrolysis of aromatic polyamides in sulfuric acid. According to the hydrodynamic data, the degree of coiling of the degradation products is the saine as that of the intact (non-degraded) macromolecules. This indicates that elements of the chernical structure responsible for the short-range order in the macromolecular chain are retained in the course of degradation.
Y1  - 1998
ER  - 
TY  - JOUR
A1  - Lavrenko, Peter N.
A1  - Okatova, Olga V.
A1  - Schulz, Burkhard
T1  - Stability and degradation of poly(p-pheneylene-1,3,4-oxadiazole) molecules in sulphuric acid
N2  - The translational diffusion coefficient and intrinsic viscosity of poly(1,4-phenylene-1,3,4-oxadiazole) molecules in 96% H2S04 have been determined at different stages of degradation of the molecules in acid solution at temperature ranging from 82 to 105 °C. The degradation rate constant, k, has been obtained from the change in the molecular weight, M, of the product degraded in solution with time at high temperature. The activation energy of the hydrolysis process was 103 ± 7 kJmol-1, which is smaller than that of aromatic polyamides in the same solvent. According to our hydrodynamic data, the degree of coiling of the molecules of degraded products does not differ from that of undegraded samples, and our conclusion was that the degradation is not accompanied with a noticeable change in the short- range interactions in the molecular chain and may be understood as a random chain scission.
Y1  - 1998
ER  -