Effects of Sequence Distribution and Physical Aging on Physical Properties of PES/PEES Random, Block, and Alternative Copolymers

IntroductionPhysical aging involves spontaneous changes in thephysical properties of polymer glasses from its nonequi-librium state to the equilibrium state. Aging affectsseveral properties such as specific volume, enthalpy,and mechanical and dielectric r…

Effects of Sequence Distribution and Physical Aging on Physical Properties of PES/PEES Random, Block, and Alternative Copolymers

The random, block, and alternative copolymers of poly ether sulfone(PES) and poly ether ether sulfone(PEES) were synthesized via three kinds of methods. The chemical structures of the three kinds of copolymers were characterized by 13 C NMR. Three kinds of PES/PEES copolymers(Tg=215 ℃), which were almost identical in composition but different in sequence distribution, were used. Their physical aging process was studied by differential scanning calorimetry(DSC) at three aging temperatures ranging between Tg-15 ℃ and Tg-25 ℃. The experimental results reveal that the alternative copolymer shows a lower enthalpy relaxation time<т>and apparent activation energy when compared with the random and block copolymers. The result of the electron-microscopy investigation of the three copolymers that were treated at 200 ℃ for 96 h indicates that the molecular aggregation of the copolymers changed from a randomly coiled amorphous phase to an ordered phase, and the ordered structure of the alternative copolymer was more distinct than that of the random phase. The experimental results of this study suggest that the motion of the segments is affected by the different molecular-chain sequence distribution.