Radical coupling of maleic anhydride onto graphite to fabricate oxidized graphene nanolayers

Abstract

Radical coupling was used to modify graphite with maleic anhydride (MAH). Azobisisobutyronitrile (AIBN) as radical generator activated MAH radically and it was reacted with defects at the surface of nanolayers. A set of batches with different reaction times (24, 48 and 72 h) were performed to obtain fully-modified nanolayers (GMA1, GMA2 and GMA3, respectively). Fourier transform infrared results approved the synthesis of MAHgrafted graphite. Thermogravimetric analysis showed that 5.9, 11.1 and 13.2 wt% of MAH was grafted onto the surface of GMA1, GMA2 and GMA3, respectively, and that was approved by X-ray photoelectron spectroscopy results. Also, X-ray diffraction patterns showed that d-spacing increased from 0.34 nm for graphite to 1.00 nm for all modified samples. However, GMA1 showed a weak peak related to graphite structure that disappeared when reaction time was increased. After modification with MAH, lamella flake structure of graphite was retained whereas the edges of sheets became distinguishable as depicted by scanning electron microscopy images. According to Raman spectra, modification progression resulted in more disorder structure of nanolayers due to grafting of MAH. Also, transmission electron microscopy images showed graphite as transparent layers while after modification, surface of nanolayers became folded due to the opposite effects of π-conjugated domains and electrostatic repulsion of oxygen-containing groups.

Effects of poly(ethylene glycol)-grafted graphene on the electrical properties of poly(lactic acid) nanocomposites

“…The peaks at 1751, 1234.7 and 1022 cm À1 were attributed to the stretching vibration of C]O and C-O-C bonds in the ester groups of PEG-g-GN owing to the hydroxyl group reaction with MAH. [25][26][27] This result suggest that PEG molecular chains were linked to the GN via ester bonds with the aid of the MAH coupling reagent.…”

“…In the GN spectrum, the stretching vibration of aromatic C]C bonds is at 1600 cm À1 . 26 Aer the MAH and PEG reaction, a wide peak appeared at 3446.1 cm À1 corresponding to the stretching vibration of hydroxyl groups. The asymmetrical and symmetrical stretching vibrations of C-H in CH 2 bonds were observed at 2925.9 and 2856.5 cm À1 , which belong to the PEG molecular chains.…”

“…The primary mass loss of the modied sample occurred in the temperature range of 130-220 C, and the weight loss was 0.91 wt%, which was assigned to the degradation of graed MAH molecules. 26 The major weight loss of approximately 2.96 wt% between 230 C and 600 C mainly originated from the pyrolysis of the graed PEG chains. 25 The SEM images are visual evidence of the graing modication success.…”

Effect of surface modification with various thiol compounds on colloidal stability of gold nanoparticles

“…Conclusively, Au‐MEA1 shows two peaks at 66.8 and 409.9 nm due to the formation of aggregations. Also, formation of hydrogen bonding between MEA and citrate molecules is another reason for the formation of aggregates at lower temperatures …”

Synthesis of dual thermo‐ and pH‐sensitive poly(N‐isopropylacrylamide‐co‐acrylic acid)‐grafted cellulose nanocrystals by reversible addition‐fragmentation chain transfer polymerization

“…PAA at pH values over its p K a (∼4.5) becomes hydrophilic due to ionization. However, protonation of the carboxyl groups results in its precipitation at pH values of lower than 4 in aqueous solutions . Copolymers based on N ‐isopropylacrylamide (NIPAAm) and acrylic acid (AA) derivatives have largely been interested because of their dual‐sensitive behavior …”