In situx-ray diffraction study ofC60polymerization at high pressure and temperature

Abstract

The C 60 polymerization was studied by x-ray diffraction in situ in the pressure range 13-18 GPa and at temperatures up to 830 K and nonhydrostatic conditions. Quenched samples were studied ex situ by Raman spectroscopy. The results of the high-pressure and high-temperature treatment are strongly dependent on the history of the sample and stress. An inaccurate increase of the pressure leads to the formation of internal stresses in the sample which gives elliptical Debye-Scherrer diffraction rings already at room temperature. During the subsequent heat treatment a soft amorphous phase is formed. At certain conditions no elliptical diffraction patterns were observed at 13 GPa and 830 K. Samples with a relatively low internal stress showed a transformation to a phase with decreased c-cell parameter compared to the known two-dimensional rhombohedral phase. The observed phase can be described as distorted cubic, but a better fit is achieved using a rhombohedral cell. It is suggested that this phase is a three-dimensional polymer with each C 60 molecule bonded to eight neighbors. This phase showed an increased hardness ͑about 37 GPa͒ and a Raman spectrum distinctly different from previously known polymeric phases.

<sup>13</sup>C NMR and Raman Studies of Fullerene-Based Poly (Acrylamides)

“…13 C NMR Spectroscopy: 13 C nuclear magnetic resonance (NMR) spectral analysis of fullerene-grafted poly (acrylamide) samples was carried in an ECX 500-JEOL NMR spectrometer using CDCl 3 as a solvent.…”

“…However, spectroscopic studies on fullerenegrafted vinyl monomers are still scarce. The present article therefore highlights 13 C NMR and Raman spectroscopic studies of fullerene-grafted poly (acrylamide) polymers. Acrylamide as a monomer is used in a variety of synthetic processes to form polymers, copolymers.…”

“…A search of the literature reveals that a lot of work has been carried out on synthesis, characterization of fullerenes, and doped fullerenes with alkali metals like potassium and rubidium ternary compounds, [4,5] poly fulleride ions in A C 60 [6] (A is potassium, rubidium, or cesium), and fullerene doped with organic cations like morpholine and acridizine [7]. The literature survey also reveals that 13 C NMR spectroscopic studies of fullerene and poly-ethylene oxide complexes, [8] magnetic resonance of solid fullerene and their compounds with alkali metals [9], superconductivity and nuclear magnetic resonance investigation of KTl 1.5 doped C 60 [10] have been carried out in past years. Synthesis and cationic photopolymerization of C 60 derivative bearing a 2,4,6-tris(epoxynonyloxy)phenyl moiety (FB9ox) [11] has been carried out.…”

“…In addition, the synthesis and determination of properties of poly (methyl methacrylate)/clay nanocomposites, prepared via in situ polymerization with nickel acetyl acetonate [Ni(acac) 2 ] catalyst in combination with methyllalumoxane [12] have also been carried out. The literature also reveals Raman spectroscopic studies on pressure-induced polymerization of C 60 at high temperature [13], rotation vibrational dynamics of C 60 [14] and the vibrational Raman spectra of C 60 [15]. High-temperature study of solid C 60 , pristine was performed by Raman spectroscopy up to 843 K [16].…”

“…The thermogravametric analysis of polyacrylamide and fullerene based poly (acrylamides) showed almost same results that the olymer is thermally and poly (acrylamide). These samples were studied by 13 C NMR spectroscopy, these spectra are given in Figures 1-8 and their comparison is given in Table 3. From the observed data, we find that there is a shift in peak values of poly (acrylamide) and fullerene, thereby showing incorporation of the polymer formed on the fullerene surface, which increases the solubility and processability of the polymer network.Raman spectroscopy yields important information about the structure of macromolecules.…”