Core double–shell cobalt/graphene/polystyrene magnetic nanocomposites synthesized by in situ sonochemical polymerization

Abstract

Core double-shell cobalt/graphene//polystyrene nanocomposites (Co/C//PS) were synthesized by in situ sonochemical polymerization technique. Commercial Co/C nanoparticles are used and successfully lead to gram-scale production of processable nanocomposite. Synthesized Co/C//PS nanocomposites result in homogeneous and dense dispersion of particles with or without additional polymeric matrix. They showed improved thermal properties such as higher initial degradation temperatures and a significant increase of glass transition temperature (i.e. 10 to 12°C) in contrast to neat PS. These results suggest that covalent bonding occurs between PS and graphene shell, and may be promoted by two surface reactions: "grafting from" when monomer is pre-immobilized on graphene and grows to polymer, and "grafting to" when presynthesized polymer is immobilized on graphene. Both mechanisms are compared and explained. HR-TEM observations revealed polymer shells of 4 to 5 nm covering Co/C nanoparticles or at least small aggregates. However, the number of layer of the graphene shell which consists of 6 to 8 regular layers on raw particles decreases to 3, this layer reduction can be explained by a partial amorphization of graphene occurring during the polymerization. Nevertheless, Co particles are still efficiently protected from oxidation as final Co/C//PS nanocomposites are able to sustain high mass-magnetization (i.e. ~ 49 emu/g for 94 % wt Co/C). First indications of satisfying mechanical cohesion are also shown by the formation of two relevant nanocomposites shapes (film and disk). In conclusion, in situ polymerization is a powerful synthesis method to produce processable high-magnetization nanocomposites.

Optical Properties of Composites Based on Graphene Oxide and Polystyrene

“…When the UV exposure time increased to 120 min (i) an increase in absorbance of the IR bands with maxima at 837, 1244 and 1273 cm −1 ; (ii) a change of the ratio between the absorbance of the IR bands peaked at 1450 and 837 cm -1 from 5 to 1.7; (iii) an up-shift of the IR band from 1743 cm −1 to 1747 cm −1 ; and (iv) the appearance of a new IR band at 1701 cm −1 were observed. This IR band is situated close to the IR band at 1683 cm −1 , reported to be assigned to the vibrational mode C=C stretching of the styrene vinyl group [28]. In our opinion, these variations support the appearance of the amorphous portions of PS and the modification of the GO sheets covalently grafted with BPO.…”

Exploring the styrene metabolism by aerobic bacterial isolates for the effective management of leachates in an aqueous system

“…The medium-to-very broad band observed between 3400 and 2700 cm À1 indicated the presence of -OH stretch. [48][49][50] The peaks observed for the cell-free medium match with those of standard PAA (Fig. 5b).…”

Non-conductive ferromagnets based on core double-shell nanoparticles for radio-electric applications

“…Complementary observations backed with Raman analysis revealed that graphene is much thinner and partially transformed into amorphous carbon (Herman et al 2015 ). Also traces of oxidized cobalt were detected by Raman spectroscopy (Herman et al 2015 ). Thus, scheme 2 is more critical.…”

“…Scheme 2 is the radical option aimed to improve dispersion and cohesion. It is detailed elsewhere (Herman et al 2015 ). For practical reasons, m i was limited to 100 mg.…”