Characterizing the Structure and Phase Transformation of Poly(ethylene Oxide)–Urea Complexes Using Terahertz Time-Domain Spectroscopy

Abstract

Terahertz time-domain spectroscopy (THz-TDS) was employed to characterize the structure and α→β phase transformation of poly(ethylene oxide) (PEO)-urea complexes. While the THz responses of α- and β-form complexes are both originated from hydrogen bonding interactions, they possess different THz absorption bands. The α-form PEO-urea complex shows two bands at 1.12 and 1.24 THz, which are vibration modes due to the hydrogen bonding among urea and between PEO and urea, respectively; the β-form PEO-urea complex shows a band at 1.48 THz, which is a vibration mode due to the hydrogen bonding among urea. A polarized THz-TDS study demonstrates that the urea-urea hydrogen bonding direction rotates 90° during the β→α transformation process. This study reveals the great potential of THz-TDS for investigating polymer-small molecule complexes.

Structure–dynamic properties relationships in poly(ethylene oxide)/silicon dioxide nanocomposites: dielectric relaxation study

“…These peaks might describe the lattice vibration of PEO crystalline regions. Similar features were also reported in the case of oxides PE and polyamide-6 [62][63][64]. Adding SiO 2 particles affects the spectral features of these resonance peaks; they become weak, broad, or even disappear.…”

“…In the same graphs, the dashed line represents the signal passes through the free space as a Ref. [62]. Here, the signals are normalized to the maximum field and position of the reference.…”