DYNAMIC-MECHANICAL BEHAVIOR OF FLUORINATED AROMATIC POLY(ETHERS)

The relaxation behavior of six fluorinated aromatic poly( ethers) was investigated using dynamic mechanical analysis. The glass transition t emperature was found to increase as the size and rigidity of linking g roups increased and varied between 168 degrees C for a dimethyl linkin g group and 300 degrees C for a bicyclic benzoate ether-linking group. For the alpha-relaxation the steepness of time/temperature plots and broadness of the loss curves could be qualitatively correlated with ch emical structure in a manner predicted by the coupling model of relaxa tion. Well-separated sub-T-g transitions were also observed, as a shou lder on the low temperature side of the alpha-peak, and as a broad, lo w loss transition around -100 degrees C. The higher temperature proces s was similar to the structural relaxation often found in quenched gla ssy polymers, while the position, intensity, and breadth of the subamb ient process was sensitive to chemical structure. (C) 1997 John Wiley & Sons, Inc.