Confinement and Distribution of the Composition in Semicrystalline/Amorphous Miscible Blends of PEKK/PEI: A Calorimetry Study

Abstract

By combining small-angle X-ray scattering and differential scanning calorimetry measurements, we analyze the widening of the glass transition measured for miscible mixtures of semicrystalline PEKK chains and fully amorphous PEI chains. The calorimetric analysis reveals that the amorphous interlamellar phase is subject to confinement effects. In addition, we measure wide composition distributions for the amorphous interlamellar and interfibrillar phases. We quantitatively identify, through careful analysis of the signals, the fraction and average composition of each amorphous phase and the composition distribution. We conclude that the final distribution of the polymer chains that do not crystallize in the interlamellar and interfibrillar phases results from the crystallization dynamics of the mixtures.

Structural Organizations of a Mesogen-Terminated Semicrystalline Polymer: Chain Termini Ordering between Polymer Crystal Lamellae

“…The structural evolutions of interlamellar amorphous chains and end groups evidently depend upon the confinement effect of crystal lamellae, which can be controlled by changing the interlamellar spacing and crystallization conditions. 9,10 However, in such a nanoconfined region, the microstructural evolution and aggregated equilibrium state of end groups are still unclear as a result of the difficulty of characterizing the interlamellarly aggregated structure by common methods.…”

“…During polymer crystallization, the chain ends, seen as defects, are generally excluded into the nanoscale amorphous region confined between crystal lamellae. − These confined end groups are initially in a non-equilibrium state and may evolve to the thermodynamic equilibrium state upon annealing and thermal treatments, which is somewhat similar to the physical aging process. , Naturally, such structural rearrangement would be more obvious for the polymers with relatively “large” end groups. The structural evolutions of interlamellar amorphous chains and end groups evidently depend upon the confinement effect of crystal lamellae, which can be controlled by changing the interlamellar spacing and crystallization conditions. , However, in such a nanoconfined region, the microstructural evolution and aggregated equilibrium state of end groups are still unclear as a result of the difficulty of characterizing the interlamellarly aggregated structure by common methods.…”