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Hydrogen bond networks in graphene oxide composite paper: Structure and mechanical properties

Evidence and attribution

Authority of statements

Distances (5.1 Å, 9.0 Å), water weight percents (1–26 wt %), and 76% volume swelling are taken from the extract as printed in the Results discussion.

Summary

The paper uses ReaxFF MD to model hydrated graphene oxide (GO) paper—stacked GO platelets with interlamellar water—and argues that hydrogen-bond networks involving oxygen functional groups and water control morphology and mechanics. The abstract states water content modulates hydrogen-bond extent/strength, interlayer spacing, and elastic moduli, while higher functional group density on platelets increases hydrogen bonding and stiffness. Simulated structural/mechanical trends are reported to agree with experiments.

Methods

ReaxFF in LAMMPS: periodic supercells with four ~3.4 nm \(\times\) 3.0 nm GO platelets, initial 7 Å interlayer gap, random epoxy/hydroxyl patterns for C\(_{10}\)O\(^1\)(OH)\(^1\) and C\(_{10}\)O\(^2\)(OH)\(^2\) stoichiometries, and random interlayer water placement. Equilibration uses NPT with Nosé–Hoover thermostat and barostat, time step 0.025 fs, heating 10→1000 K over 625 fs, anneal at 1000 K for 625 fs, quench to 300 K over 625 fs, then 300 K, zero pressure for 4.25 ps. Mechanical analysis runs NVT at 300 K; atomic displacements sampled every 50 steps feed fluctuation-based elastic constants via the displacement-correlation approach cited in the article (references to Pratt and Meyers et al. in the PDF). Water content spans ~1–26 wt %.

Findings

Interlayer spacing increases from ~5.1 Å (low water) to ~9.0 Å at ~26 wt % water for the C\(_{10}\)O\(^1\)(OH)\(^1\) models, with ~76% volume swelling over that range. Spacing vs. water is approximately linear and similar for both oxidation stoichiometries at comparable hydration. H-bond counts rise roughly linearly with water; C\(_{10}\)O\(^2\)(OH)\(^2\) supports more H-bonds than C\(_{10}\)O\(^1\)(OH)\(^1\) at the same water content. ReaxFF optimal O···H distance ~2.55 Å with ~320 meV interaction strength matches typical H-bond scales cited for comparison. Modeled structural/mechanical trends align with experimental X-ray gallery heights (~6–11 Å cited) and humidity-dependent modulus changes.

The authors emphasize that water-mediated H-bond networks couple swelling to mechanical stiffening, so GO paper cannot be treated as a simple graphite stack with fixed interlayer spacing.

Limitations

Reactive MD captures graphene oxide chemistry only approximately; laboratory samples exhibit polydisperse oxidation and defect distributions. extraction_quality is partial; elastic moduli and stress–strain data are in the PDF figures.

Relevance to group

Demonstrates ReaxFF for oxide–water–carbon hydrogen-bonded assemblies relevant to interfaces, nanocarbon, and composite mechanics threads in the corpus.

Citations and evidence anchors

  • DOI: 10.1021/nn901934u.
  • PDF: papers/ReaxFF_others/Medhekar_Shenoy_grapheneoxide_ACSNano_2010.pdf.
  • Extract: normalized/extracts/2010medhekar-venue-paper_p1-2.txt.