From Trans to Cis Conformation: Further Understanding the Surface Properties of Poly(m-phenylene isophthalamide)

Abstract

Controlling the membrane surface properties such as hydrophobicity and hydrophilicity is critical to achieving desirable performance. For a long time, the difference between the surface wettabilities of superhydrophilic poly( m -phenylene isophthalamide) (PMIA) electrospun nanofibrous membranes (ESMs) and the superhydrophobic parent material is believed to arise from the poling effect induced by the electrospinning process and wicking caused by the porous membrane structure. In this study, the short-term poling effect was eliminated using a reference, centrifugally spun nanofibrous membrane that has a similar fiber morphology and specific surface area to those of the ESM; consequently, we investigated the changes in the surface properties of the ESM in detail. Chemical analysis by angle-resolved X-ray photoelectron spectroscopy revealed that the N and O concentrations are greater at the surface of the ESM. In addition, analysis of the membranes by attenuated total reflectance Fourier-transform infrared spectroscopy and Raman spectra revealed that large amounts of cis conformations of the amide bonds appeared on the surface of ESM after the electrospinning process. The results indicate that the remarkable surface properties of PMIA ESMs mainly arise from the change in the conformation of the amide groups from the stable trans form to the cis form. This change was confirmed by the subsequent in situ growth of Pt nanoparticles and the excellent dye adsorption capacity of the membrane.

Achieving superiorly highheat‐dimensionalstability, high strength, and good electrochemical performance for electrospun separators in powerlithium‐ionbattery through building unique condensed structure based on polyimide and poly (m‐phenylene isophthalamide)

“…Specifically, compared with spectra of PMIA and PI/PMIA, that of C-PMIA not only has stronger absorption intensities of the stretching vibration of free N-H (3000-3500 cm À1 ) and the bending vibration of N-H (1541 cm À1 ), 46 but also shows red-shifts including the stretching vibration of C=O (1656 cm À1 ), the in-plane bending vibration of N-H (1608 cm À1 ) 47 and out-of-plane bending vibration of N-H (783 cm À1 ), 48 suggesting that hydrogen bonds have been broken because amide groups of PMIA have significant torsion and out-of-plane deformation under high voltage electric field during the electrospinning process. 49 Similar phenomenon was also reported by Wang's group. 48 Above results such as red-shift of absorption wavenumber and absorption intensity are also found when analyzing the spectra of PMIA and PI/PMIA.…”

Recent Progress in Preparation and Anti-Icing Applications of Superhydrophobic Coatings

“…During a long period, the difference in the surface wettability between superhydrophilic poly(m-phenylene isophthalamide) (PMIA) electrospun nanofibrous membranes (ESMs) and the superhydrophobic parent material was believed to arise from the poling effect induced by the electrospinning process. To eliminate the poling effect, Ouyang et al prepared a PMIA ESM [116], and used a centrifugally spun nano fibrous membrane (CSM) as a reference sample. Finally, the changes of surface properties of the membranes at the molecular level were investigated.…”

Core–Shell Structured Polyamide 66 Nanofibers with Enhanced Flame Retardancy

“…The electrospinning of synthetic polymers continues to grow in popularity as a method because it not only enables fine control over the architecture − and dimensions of the resultant nanofibers, but it can also be conveniently scaled . As a result, electrospun nanofibers have been extensively used in a variety of applications, including drug delivery, tissue engineering, and energy harvesting .…”