Characterization of the stable and metastable poly(ethylene oxide)–urea complexes in electrospun fibers

Abstract

Solution electrospinning was used for the first time to prepare nanofibers of the stable (α) and metastable (β) complexes between poly(ethylene oxide) (PEO) and urea. Both types of fibers were highly crystalline and presented a large level of molecular orientation. Detailed characterization of the ill‐studied β complex was performed using wide angle X‐ray diffraction (WAXD), infrared spectroscopy, and differential scanning calorimetry (DSC). Results reveal that it possesses a 3:2 PEO:urea stoichiometry and suggest that it belongs to the orthorhombic system with a = 1.907 nm, b = 0.862 nm, and c = 0.773 nm. The PEO chains are oriented along the fiber axis and present a conformation significantly affected by strong hydrogen bonding with urea when compared with the pure polymer and the stable complex. A layered structure model is suggested for the metastable complex, in which the urea molecules would be arranged into a ribbon‐like structure intercalated between two PEO layers. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1903–1913, 2008

Characteristics and 3D formation of PVA and PEO electrospun nanofibers with embedded urea

“…Many attempts have been made to fabricate nanofibers containing high amount of urea, but the process have been shown problematic. Liu et al in 2008 and Isakov et al in 2010 electrospun PEO and PVA nanofibers containing urea . Both research groups studied the optical characteristics of the urea embedded nanofibers.…”

Flexible, Solid Electrolyte-Based Lithium Battery Composed of LiFePO4Cathode and Li4Ti5O12Anode for Applications in Smart Textiles

“…It has been reported that adding urea into the PEO film promotes crystallinity via formation of the highly crystallized complexes. Particularly, formation of specific complexes between PEO and urea was reported in 37,38 for the two PEO:urea molar ratios 3:2 and 4:9. The two complexes were suggested to be of a layered or channel type.…”

Electrical Characteristics of Poly(ethylene oxide)-urea Complex Films

“…1(a), the N-H stretching bands in the spectrum of the film with a urea concentration of 0.1 M were observed at lower frequencies compared to those in the spectra of the film with urea concentrations of more than 0.2 M. This indicates that the complex with a urea concentration of 0.1 M consists mainly of the β-phase and that the other complexes with urea concentrations of more than 0.2 M consist mainly of the α-phase [9]. Therefore, the β-phase of the complex transforms into the α-phase with an increase in the urea concentration [4]: this transformation is hereafter, referred to as the β-α transition.…”

“…Some parts of the β-phase complexes can be transformed into α-phase complexes by increasing the urea mole fraction or by heating. The β-α transition of PEO-urea complexes and their structural phase diagrams have been intensively studied [2,[5][6][7][8][9][10].…”