Molecular Mobility in Para-Substituted Polyaryls. 3. Low-Temperature Dynamics

• Published in: Macromolecules 1996-12, Vol.29 (26), p.8343-8348
• Main Authors: David, L, Girard, C, Dolmazon, R, Albrand, M, Etienne, S
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed Matter; Exact sciences and technology; Materials Science; Mechanics; Mechanics of materials; Organic polymers; Physicochemistry of polymers; Physics; Properties and characterization; Rheology and viscoelasticity
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma960181i

The low-temperature mechanical relaxations in poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene [poly(aryl ether ether ketone, PEEK], poly(thio-1,4-phenylene) [poly(phenylene sulfide), PPS], and poly(oxy-1,4-phenylenesulfonyl-1,4-phenylene), [poly(aryl ether sulfone), PES] are investigated. All three polymers exhibit a low-temperature γ relaxation, in the temperature range from 40 to 100 K at 1 Hz. The apparent activation energies for the γ relaxations (15−25 kJ/mol) are close to the values derived from empirical force field molecular mechanics calculations of the “crankshaft motion” in an isolated chain portion. Only polymers with a polar interaromatic bridge (PEEK and PES) exhibit another secondary β relaxation, in the temperature range from 100 to 250 K at 1 Hz. Moreover, the apparent activation energies of the β processes are significantly higher than the activation energies of the γ relaxations. Therefore, it is concluded that polar intermolecular interactions play an important role in the molecular events leading to the β relaxation, whereas the γ relaxation is due to conformational changes mostly controlled by an intramolecular energy.