Two-Dimensional Subnanometer Confinement of Ethylene Glycol and Poly(ethylene oxide) by Neutron Spectroscopy: Molecular Size Effects

Abstract

We explore the effects of chain size on the structure and dynamics of ethylene glycol (EG) and poly(ethylene oxide) (PEO) intercalated in graphite oxide (GO). To this end, EG as well as a PEO series of increasing chain length have been studied by means of high-resolution inelastic neutron spectroscopy. The neutron experiments are complemented by X-ray diffraction, differential scanning calorimetry, Fourier-transform infrared spectroscopy, and Raman scattering. We find that EG is accommodated in a layer of thickness ∼3 Å within the GO substrate and adopts a preferential, yet largely disordered, gauche conformation. Longer PEO chains give rise to a layer thickness in the range ∼3.0−3.4 Å characterized by planar zigzag (trans−trans−trans) conformations. Moreover, we observe a strong reduction of vibrational motions for the confined EG and polymer phases, as clearly evidenced by the disappearance, shift, and/or broadening of mode-specific inelastic neutron scattering spectral features, as well as by the complete suppression of crystallization. All of these effects are surprisingly insensitive to the length of the PEO chains.

Molecular Insights into Bulk and Porous κ2P,N‐PTA Metal‐Organic Polymers by Simultaneous Raman Spectroscopy and Inelastic Neutron Scattering

“…Inelastic neutron scattering has been successfully used to characterize the structure and the properties of a variety of organic polymers and metal‐organic frameworks …”

“…Inelastic neutron scattering has been successfully used to characterize the structure and the properties of a variety of organic polymers [18][19][20][21][22][23][24] and metal-organic frameworks. [25][26][27][28] Nevertheless, to the best of our knowledge, this is the first time in which a metal-organic polymer is studied by means of this technique.…”

Understanding the Structure and Dynamics of Nanocellulose-Based Composites with Neutral and Ionic Poly(methacrylate) Derivatives Using Inelastic Neutron Scattering and DFT Calculations

“…The INS spectrum of PHEMA is shown in Figure 3 (top). The most prominent features, related with the O-CH 2 -CH 2 -OH side fragment, were easily identified, as they could be directly derived from the INS spectrum of ethylene glycol (Figure 3, bottom) [36]. For instance, the band pair at ca.…”

“…This approach, required for amorphous materials and described in detail by Harrelson et al [34], has been successfully used to infer the local structure of polymers from INS spectra. For instance, it has been used to experimentally assess the random nature of 2,4-poly(ethylene furanoate) [35], to identify the zigzag structure of confined poly(ethylene oxide) [36] and to conclude on the side chains flattening in doped poly(hexylthiophene) [34].…”

“…This approach, required for amorphous materials and described in detail by Harrelson et al [34], has been successfully used to infer the local structure of polymers from INS spectra. For instance, it has been used to experimentally assess the random nature of 2,4-poly(ethylene furanoate) [35], to identify the zigzag structure of confined poly(ethylene oxide) [36] and to conclude on the side chains flattening in doped poly(hexylthiophene) [34].The first studies dealing with the characterization of cellulose by INS were published by Muller and coworkers two decades ago [37,38]. In these studies, the authors were able to identify the bands assigned to O−H and C−H stretching modes, together with the angle bending motions involving hydrogen atoms (1180−1500 cm −1 ), OH out-of-plane modes (550−950 cm −1 ) and C−C and C−O torsional modes (<300 cm −1 ) in different types of cellulose [37].…”