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Russ.Chem.Bull., Int.Ed., Vol. 58, No. 8, August, 2009
Kvashina et al.
Results and Discussion
existence of the residue indicates the presence of titanium
in the product. According to the elemental analysis data
(Н/С = 1.544), the product obtained is characterized by
increased content of carbon compared with common polyꢀ
ethylene, which could be explained by the presence of
both polyethylene and fullerene.
Indeed, the following absorption bands are present in
the IR spectra of the film formed, ν/cm–1: 718 (δ(СН2))
(medium), 728 (δ(СН2)) (medium), 1183 (С60) (weak),
1430 (С60) (weak), 1462 (δ(СН2)) (medium), 1472
(δ(СН2)) (medium), 2850 (ν(CH2)) (strong), 2918
(ν(СН2)) (strong). The spectrum observed comprises two
spectra: a spectrum characteristic of polyethylene,6 and a
spectrum of fullerene.7 Weak absorption bands at 1183
and 1432 cm–1 are referred to vibrations of the fullerene
molecule.7
The polyethylene component is in the crystalline state.
The crystallinity of polyethylene is confirmed by splitting
of absoption bands of scissor and rocking vibrations of
СН2 by 10 cm–1 (doublets at 1462, 1472 cm–1 and 728,
718 cm–1, respectively).8 According to DSC data, the deꢀ
gree of crystallinity of polyethylene film is 79.4% (ΔНm =
= 232.7 J g–1), and Тcr = 111.16 °С. No adsorption bands
at 1378 and 2960 cm–1 typical of the Me groups are present
in the IR spectra, which suggests the linear nonbranched
structure of polyethylene obtained.8
Halfꢀwidths of the absorption bands of the stretching
vibrations of С—Н at 2918 and 2850 cm–1 in the IR specꢀ
tra of polyethylene obtained on catalyst 1 are 13.5 and
9 cm–1, respectively, which is ~30% smaller than in the
case of the Zeigler catalysts.9
The Raman spectrum of the product (ν/cm–1): 278
(С60) (strong), 436 (С60) (weak), 497 (С60) (strong), 711
(С60) (weak), 773 (С60) (weak), 1063 (polyethylene)
(weak), 1108 (С60) (weak), 1131 (polyethylene) (weak),
1249 (С60) (weak), 1286 (polyethylene) (medium), 1438
(polyethylene, δ(СН2)) (medium), 1468 (С60) (strong),
1574 (С60) (medium), 2844 (polyethylene, ν(СН2))
(strong), 2881 (polyethylene, ν(СН2)) (strong). It conꢀ
sisted of the spectra of polyethylene and fullerene. The
frequences and intensities of the observed fullerene bands
are in agreement with the literature data.10 The characterꢀ
istics of polyethylene bands in the Raman spectrum meaꢀ
sured are also in agreement with the published ones.6
Thus, compound 1 is the catalyst for ethylene polyꢀ
merization. It should be noted that the rate of polymerizaꢀ
tion and the yield of the polymer is higher in the case of
the fullereneꢀcontaining catalyst 1 than in the case of oxyꢀ
genꢀcontaining titanium comlex2 under similar conditions,
i.e., catalyst 1 is more efficient in polyethylene polyꢀ
merization.
Bisarenetitanium(0) complexes are extremely sensiꢀ
tive to oxygen.1—3 Mixing, using a vacuum setup, of a red
solution of dibenzenetitanium(0) in benzene with a bright
violet saturated solution of fullerene containing undisꢀ
solved fullerene in benzene affords a fine dark precipitate
1, the solution becomes pale violet. Then ethylene was
added to the system with stirring. The kinetics of ethylene
polymerization in the presence of complex 1 in the initial
period of the reaction is presented in Fig. 1. Polymerizaꢀ
tion begins with short induction period (5 min). The proꢀ
file of the kinetic curve suggests its steadyꢀstate character.
The rate of polymerization retains during the first four
hours, after which it begins to decrease. The duration of
polymerization process is 113 h under these conditions.
The yield of polyethylene after the first hour is 13 g (g Ti)–1,
the final yield of polyethylene is 396 g (g Ti)–1. After comꢀ
pletion of the reaction, the excess of fullerene was removed
from the product by washing with benzene in a vacuum
setup until the colorless benzene washings were obtained.
The reaction product formed in the form of film coverꢀ
ing the walls of the reaction vessel. The film color varied
from pale brown to beige depending on its thickness. This
can probably be explained by the presence of catalyst 1
remained. The melting point of polyethylene determined
by DSC is 133 °С. The molecular mass of polymer deterꢀ
mined by viscosimetry is 1 634 kDa.
It should be noted that in contrast to previous work2
the use of fullerene instead of oxygen changes the properꢀ
ties of polyethylene formed: the polymer represents a film
coating rather than separate spherical particles as in case
of oxygenꢀcontaining catalyst.
The elemental analysis of the polyethylene film obꢀ
tained gives (%): С, 88.00; Н, 11.32; the residue 0.1. The
Δp/kPa
6
5
4
3
2
1
0
10
20
30
40
50
t/min
The mechanism of the interaction of fullerene with
dibenzenetitanium(0) is unclear. It can be assumed that
the interaction results in the formation of fullereneꢀconꢀ
taining titanium compound like chargeꢀtransfer complex.
Fig. 1. The time dependence of ethylene consumption during its
polymerization in the presence of catalyst 1 in the initial period
of the reaction. Reaction conditions: 22 °С, pressure 72 kPa,
benzene (3 mL), 6•10–5 mmol of Ti, 7.6•10–5 mmol of fullerene.