Brill Transition in Polyamide 1012 Multiblock Poly(tetramethylene oxide) Copolymers: The Effect of Composition on Hydrogen-Bonding Organization

Abstract

The effect of composition on the Brill transition of polyamide-based copolymers was systematically investigated with the synthesized polyamide 1012 (PA1012) multiblock poly(tetramethylene oxide) (PTMO) copolymers. By using the X-ray scattering and infrared spectroscopy techniques, it was found that the amorphous PTMO segments accelerated the reorganization of hydrogen sheet (H-sheet) structures of PA1012 segments during rapid cooling from the melt, resulting in an α-phase with a higher crystal perfection index (CPI) for a lower PA1012 content (WPA) copolymer. For low-WPA copolymers, the α-phase is completely transformed to the γ-phase at a lower Brill temperature (TB) at a given CPI, which is attributed to the enhanced chain mobility by the PTMO segments. All the studied samples (WPA in the range of 1.00 to 0.32) are superimposed to form a master curve of TB/TB,CPI=1 = 0.9 × CPI + 0.08, where TB,CPI=1 is the theoretical TB for each sample at its corresponding perfect H-sheet structure. The results imply that the thermodynamic mechanism of Brill transition in the PA1012 homopolymer and PA1012-PTMO copolymer is equivalent. Moreover, this master curve can be used to quantitatively estimate the TB of PA1012-PTMO copolymers with a given composition and is expected to be applied in polyamide-based copolymers composed of different comonomers by determining their own characteristic parameter of TB,CPI=1.