Endo, Kiyoshi

Inukai, Akihiro

Otsu, Takayuki

Osaka City University Repository

Mem. Fac. Eng., Osaka City Univ., Vol. 38, pp.23-25 (1997)
Polymerization of Alkyl Methacrylates with V(acac)J-AIEtJ Catalyst
Kiyoshi Endo, Akihiro Inukai, and Takayuki Otsu
(Received September 30, 1997)
Synopsis
Polymerizations of methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl meth-
acrylate, and tert-butyl methacrylate with V(acac)3-AIEt3 catalyst were investigated. It was found that
all monomers examined polymerized with the V(acac)3-AIEt3 catalyst, and the polymerization rates
'\Tere influenced by the alkyl ester substituents of alkyl methacrylates. Since the polymerization of the
alkyl methacrylates did not take place with each single component at -78°C, both components are
necessary to produce the active site for the polymerization.
KeJ'lvords: Polymerization, Alkyl methacrylates, Isopropyl Methacrylate, tert-Butyl Methacrylate,
V(acac)3-AIEt3 Catalyst
Introduction
Polymerizations of MMA with Ziegler-Natta catalysts, including V-based catalysts, have been
reported 1-12), In a previous paper 13), we reported that vanadium(III) acetylacetonate [V(acac)3l in
combination with AIEt3 induced the polymerization of methyl methacrylate (MMA) under mild
conditions to give polymers. From the analysis of a tacticity of the polymers, it was confirmed that
multi active sites were produced with the V(acac)3-AIEt3 catalyst.
The polymerization activities of alkyl methacrylates were accepted to depend on ester alkyl
substituents in radicalI4-16) and anionic I7- 19) polymerizations. Such effects are also expected to be
observed in the Ziegler-Natta polymerizations of the alkyl methacrylates. However, the polymeriza-
tions of various alkyl methacrylates with V-based catalysts under same conditions were not investigated.
Thus, it is interesting to know the effect of ester alkyl substituents in the polymerization of alkyl
methacrylates with the V(acac)3-AIEt3 catalyst.
The present paper will describe the results for the polymerizations of MMA, ethyl methacrylate
(EMA), isopropyl methacrylat~ (iPMA), n-butyl methacrylate (nBMA), and tert.-butyl methacrylate
(tBMA) with V(acac)3-AIEt3 and AIEt3 catalyst.
Experimental
Materials
Alkyl methacrylates purchased from Tokyo Kasei Chern. Co. were used after fractional distillation
over a calcium hydride. AIEt3 supplied from Tosoh-Akzo Chern Co. was used without further
purification as a toluene solution. V(acac)3 purchased from Aldrich Chern. Co. was used as received.
Toluene and other reagents were used after purification by conventional methods.
Polymerization
Polymerizations were carried out in a sealed glass tube with shaking at constant temperature for a
given time. The charging of the required amounts of reagents into the tube with a rubber septum with
a connection to the vacuum system was performed by syringes through the rubber septum under
nitrogen atmosphere. After the polymerizations, the contents in the tube were poured into a large
amount of methanol containing a small amount of hydrochloric acid to precipitate the polymers
formed in the polymerizations of iPMA, nBMA, and tBMA. In the case of the polymerization of
EMA, a large amount of methanol containing about ten percent of water was added to precipitate the
23
24
polymers formed. Polymer yields were calculated by gravimetry.
Characterization ofpolymer
The number-average molecular weight of the polymer (Mn) and the molecular weight distribution
(M,v/Mn) ,vas estimated by GPC using Tosoh RE-800 series GPC instrument in THF at 38°C as
calibrated with polystyrene standard. The tacticity of the polynlers was determined from IH NMR
spectra using lEOL GX-400 NMR spectrometer measured in CDCI3 at 25°C. A methyl esterification
of the poly(alkyl methacrylate) was performed by the following procedure; the polymers were first
hydrolyzed in a concentrated sulfuric acid at room temperature for a week, and then poly(methacrylic
acid) produced by hydrosis was esterified with diazomethane in THF leading to poly(MMA) for
measuring a tacticity of the polymers.
a) [monomer] = 2.0 mol/L, [AI]=0.2 mol/L.
Table 2 Polymerization of alkyl methacrylate
with the AIEt] catalyst in tolueneat -78°Ca)
Table 1 Polymerization of alkyl methacrylate with the V(acac)3-AIEt3
catalyst in toluene at -78°Ca)
57.3
o
o
31.6
trace
trace
Yield
(%)
Tacticity (%)
I H S
1.5 22.0 76.5
11.1
24
24
24
24
(h)
Time
MMA
EMA
iPMA
tBMA 90 trace
nBMA
Monomer
MMA 46.0 13.0 1.4 1.5
EMA 24.0 14.3 2.5 1.4
iPMA 6.0 35.4 29.4 1.5
nBMA 24.0 27.0 2.2 2.6
tBMA 24.0 30.0 1.0 2.4 11.1 34.5 54.3
Monomer Time Yield M:ri
(h) (%) xl 0-4
a) [monomer] = 2.0 mol/L, [V]=20 mmol/L, [AI]/[V]=10.
Results and Discussion
Table 1 shows the results of the polymerizations of alkyl methacrylates with V(acac)3-AIEt3 catalyst
in toluene at -78°C. All alkyl methacrylates examined polymerized with V(acac)3-AIEt3 catalyst to
giving high molecular weight polymers more than 104. The polymerization rates were found to depend
on ester alkyl substituents of alkyl methacrylates, and decreased in the following order; isopropyl >
tert.-butyl > n-butyl >
ethyl > methyl, i.e.,
the polymerizations of
alkyl nlethacrylates
having more bulky
alkyl substituents of the
ester groups were faster
than those having less
bulky alkyl groups.
Previouslyl), we
pointed out that both
catalyst compoments,
i.e., V(acac)3 and AIEt3
were necessary to form
active sites for the polymerization of MMA. To check this point for other methacrylate monomers,
the polymerizations of the alkyl methacrylates with AIEt3 at -78°C were investigated, and the results
are listed in Table 2. The poly-merizations of all alkyl methacrylates hardly took place with the
AIEt3 catalyst. Moreover, the V(acac)3 catalyst was not not polymerized these monomers at -78°C.
Accordingly, it is clear that both catalyst components are necessary to produce active sites for the
polymerizations of RMA's.
The molecular weight distribution of the
polymer (MwlMn ) as listed in Table 1 was
relative narrow, and GPC elution curves also
showed monomodal. This indicates that the
polymerizations of the alkyl methacrylates
proceed at a single active site.
The triad tacticity of the polymers
obtained with the V(acac)3-AIEt3 catalyst at-
78°C were estimated from IH NMR spectra of
the poly-mers. The triad tacticities of the
poly(iPMA) and poly(tBMA) were measured
as the poly(MMA) after methyl esterification
of their polymers according to the procedure
25
7.02
1.58
2.29
4.73
3.85
40
1.2
1.5
2.1
0.9
4.0
30
Elution counts
20
Fig. 1 GPC elution curves for
poly(iPMA) obtained with
(1) V(acac)3-AIEt3 catalyst,
. (2) AIEt3 catalyst at 30°C.
9.6
21.4
90.3
4.4
--100
Yield (%)Monomer
MMA
EMA
iPMA
nBMA
tBMA
mentioned In theexperimentaI part.
From the splitting reso-nance of a- Table 3 Polymerization of the alkyl methacrylates with
methyl of MMA units, the triad tacticities the V(acach-AlEt3 catalyst in toluene for 1.0 at 30°Ca)
of original poly(iPMA) and poly(tBMA)
were determined, and the tacticities of the
polymers are also listed in Table 1. The
mm contents of the polymers obtained
from iPMA and tBMA were higher than
that obtained from MMA, i.e., the ester
alkyl substituents influenced not only the
polymerization rates but also the stereo-
regularity of the polymers, i.e., the alkyl
methacrylates having bulky ester alkyl a) [monomer] = 2.0 mollL, [V]=20 mmoIlL,[AI]/[V]=IO.
substituents gave more mm contents as comparison with the
alkyl methacrylate having less bulky ester alkyl substituents.
To check the influence of tempe-rature, the polymeriza-
tions were carried out with the V(acac)3-AlEt3 catalyst at
30°C, and the results are shown in Table 3. All monomers
examined gave high molecular weight polymers. The
polymerization rates of the alkyl methacrylates at 30°C were
faster than that at -78°C.
The GPC elution curves obtained with the polymerization
of iPMA are shown in Fig. 1. The curves of polymer obtained
at 30°C gave bimodal. The AIEt3 catalyst also gave a poly-
mer at 30°C, and its molecular weight was low as shown in
Fig. 1. Thus, It is clear that the multi active sites were
produced with the V(acac)3-AlEt3 catalyst at 30°C.
References
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Polymerization of Alkyl Methacrylates with V(acac)_3-AlEt_3 Catalyst

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Polymerization of Alkyl Methacrylates with V(acac)_3-AlEt_3 Catalyst

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