Synthesis of 2-formyl-1-(p-vinylphenyl)cyclopropane and its polymerization and copolymerization with styrene

Article abstract of DOI:10.1134/S1070427208040204

2-Formyl-1-(p-vinylphenyl)cyclopropane was prepared, and its homopolymerization and copolymerization with styrene were performed. The effect of the substituent on the monomer reactivity and the photosensitivity of the copolymer obtained were examined.

Full text of DOI:10.1134/S1070427208040204

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2008, Vol. 81, No. 4, pp. 672 675.
Pleiades Publishing, Ltd., 2008.
Original Russian Text
K.G. Guliev, 2008, published in Zhurnal Prikladnoi Khimii, 2008, Vol. 81, No. 4, pp. 636 639.
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Synthesis of 2-Formyl-1-(p-vinylphenyl)cyclopropane
and Its Polymerization and Copolymerization with Styrene
K. G. Guliev
Institute of Polymeric Materials, National Academy of Sciences of Azerbaijan, Sumgaiyt, Azerbaijan
Received July 5, 2007
Abstract 2-Formyl-1-(p-vinylphenyl)cyclopropane was prepared, and its homopolymerization and co-
polymerization with styrene were performed. The effect of the substituent on the monomer reactivity and
the photosensitivity of the copolymer obtained were examined.
DOI: 10.1134/S1070427208040204
Hb
c C=C
Ha
Functional polymers find growing use in micro-
electronics owing to their high heat resistance, good
electrical properties, and high deformation-and-strength
characteristics. Such a set of properties makes some
functional polymers useful for preparing protective
and insulating layers in the production of microelec-
tronic devices and circuits. A topological pattern is
usually created in a polymer film by optical photo-
lithography using a multilayer system of resists, or by
appropriate modification of the polymer to make it
photosensitive [1 5]. The latter alternative has a num-
ber of significant advantages, as it considerably sim-
plifies and reduces the process of pattern formation
and increases the resolving power of lithography.
H
Pyridine CrO3
O
H
CH2OH
C
The structure of the aldehyde prepared was deter-
mined from the IR and H NMR spectra. The results
of spectroscopic studies and GLC analysis show that
FVPC is a mixture of two geometric isomers, cis and
trans, in a 30 : 70 ratio.
1
The IR spectrum of FVPC shows absorption bands
at 1635 1640, 1035 1045, 1500, and 1605 cm ,
1
characteristic of the vinyl group in cyclopropane and
benzene rings. It also contains a band at 3010 cm
The aim of this study was to prepare a new formyl-
substituted cyclopropylstyrene monomer, 2-formyl-1-
(p-vinylphenyl)cyclopropane (FVPC), and to examine
its radical polymerization and copolymerization with
styrene. We also intended to study systematically
the influence exerted on the photosensitivity of cyclo-
propane-containing polymers by the substituent at
the cyclopropane ring in the pendant chain of the
macromolecule [6, 7].
1
characteristic of the aldehyde C H bond and a band
1
at 1709 cm corresponding to the C=O group.
1
In the H NMR spectrum, the vinyl proton signals
are observed at 6.76 (Ha), 5.38 (Hb), and 5.80 ppm
(Hc). The aromatic ring protons are manifested at
6.60 7.30 ppm. The aldehyde proton appears as a sin-
glet at 9.1 ppm.
2-Formyl-1-(p-vinylphenyl)cyclopropane is a new
promising monomer for preparing polymers with
valuable properties for microelectronics. FVPC was
synthesized as follows. First, we prepared 2-ethoxy-
carbonyl-1-(p-vinylphenyl)cyclopropane. Then, this
ester was reduced to 2-hydroxymethyl-1-(p-vinyl-
phenyl)cyclopropane [8], which was subsequently oxi-
dized to FVPC according to [9]:
The vinyl proton signals are shifted downfield rela-
tive to unsubstituted styrene (Ha, 6.4; Hb, 5.11; Hc,
5.58 ppm). This shift is mainly caused by the meso-
meric effect of substituents; specific distribution of
the electron density in the cyclopropane ring also
has a certain effect. The spectra suggest that all
the synthesis steps leave the vinyl group and cyclo-
propane ring intact.
672

SYNTHESIS OF 2-FORMYL-1-(p-VINYLPHENYL)CYCLOPROPANE AND ITS POLYMERIZATION 673
Copolymerization of FVPC (M1) with styrene (M2) in benzene at 333 K ( [M] = 0.2 M; 0.1% AIBN)
Copolymer composition, mol %
FVPC fraction in
starting mixture, mol %
Aldehyde
group, %
1
Yield, %
[ ], dl g
m1
m2
90
75
50
25
10
12
8.5
10
80
7.5
15.5
13.67
10.6
7.06
3.79
1.19
1.08
1.05
92.19
81.10
63.97
41.86
22.48
7.81
18.9
37.03
58.14
77.52
From the monomer synthesized, we prepared new
homo- and copolymers. The FVPC polymerization
was performed in the bulk and in benzene at 70 C in
the presence of azobis(isobutyronitrile) (AIBN). Poly-
merization in the bulk yields 1 2 wt % of an insolu-
ble fraction. In polymerization in solution, no insolu-
ble fraction is formed. The polymerization occurs
without induction period at a constant rate up to 85%
conversion. The polymers after precipitation and dry-
ing to constant weight are white powders readily sol-
uble in benzene, chloroform, and dimethylformamide.
To reveal specific features in the behavior of FVPC
under the conditions of radical polymerization, we
also studied its copolymerization with styrene.
The structures of copolymer macromolecules ob-
tained at various conversions and containing units of
both monomers in the macrochain were examined by
IR spectroscopy. The IR spectra of copolymer sam-
ples prepared at various ratios of the starting mono-
mers contain absorption bands of the aldehyde car-
1
bonyl group at 1709 cm and bands of the cyclo-
1
propane ring at 1035 1040 cm . Analytical data
confirm the occurrence of the copolymerization. We
found that the radical copolymerization of the starting
monomers follows regular trends characteristic of
vinyl monomers. The polymers prepared contain re-
active formyl-substituted cyclopropane fragments in
the pendant chains.
The structure of the polymer was examined by IR
and H NMR spectroscopy, and the polymer composi-
tion was determined by elemental analysis.
1
We found that the radical polymerization occurs
via vinyl groups with the formation of macromole-
O
H
The ratio of styrene and FVPC monomer units in
the copolymer macromolecule was determined by
elemental analysis and titration of aldehyde groups.
The results are listed in the table.
CH CH C
CH2
cules containing
pendant fragments.
This is confirmed by the fact that the cyclopropane
ring and aldehyde group remain intact in the course
of polymerization. Comparison of the IR spectra of
the starting FVPC and polymer thereof shows that
the positions and intensities of the absorption bands
of the cyclopropane ring and aldehyde group do not
change noticeably, whereas the bands of the vinyl
group disappear. The same conclusion follows from
These data show that FVPC is a more active mono-
mer than styrene.
The higher activity of FVPC, compared to styrene,
also following from the calculated Fineman Ross
copolymerization constants [10] of FVPC, may be due
to conjugation of the cyclopropane ring with an elec-
tron-withdrawing formyl substituent, which is consist-
ent with the data of [11, 12]. The copolymerization
constants, r1 = 1.25 0.025 and r2 = 0.32 0.01, dem-
onstrate the effect of the carbonyl group in the mono-
mer on the electronic structure of the whole molecule.
This conclusion is consistent with the UV spectra in
which the absorption peaks of FVPC and styrene are
observed at essentially different wavelengths: 300 and
240 nm, respectively.
1
the H NMR spectra.
1
The H NMR spectrum contains signals from pro-
tons of the benzene ( 6.85 7.25 ppm) and cyclo-
propane ( 0.75 1.75 ppm) rings. The aldehyde pro-
ton gives a signal at 9.1 ppm. The signals of the vinyl
protons fully disappear.
1
The IR and H NMR data suggest the following
structure of the polymer:
In the monomer, the vinyl group is activated and
the protonating radical is stabilized by not only J,
but also M effect of the aldehyde group.
CH2=CH
CH2=CH
n
AIBN
n
O
H
O
H
Our results and published data suggest that this
behavior of FVPC is primarily due to the effect of
C
C
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 4 2008

674
GULIEV
drazine hydrochloride, or aniline with the aim to
obtain polymers with required properties.
EXPERIMENTAL
2-Formyl-1-(p-vinylphenyl)cyclopropane was pre-
pared by the reaction of 2-hydroxymethyl-1-(p-vinyl-
phenyl)cyclopropane with a pyridine CrO3 complex
solution (Sarett reagent) [9]; bp 88 90 C/1 mm Hg,
n2D0 1.5810, d420 1.082, MRD: calculated 52.15, found
52.98.
Found, %: C 83.52, H 6.35.
Photosensitivity
rene vs. copolymer composition.
of copolymer of FVPC (M ) with sty-
1
Calculated, %: C 83.72, H 6.98.
Homopolymerization of FVPC and its copolymeri-
zation with styrene were performed in the bulk and in
a benzene solution at 333 K in the presence of AIBN.
The molar ratios of the monomers are listed in the ta-
ble. The reaction was performed in ampules under ni-
trogen for 3 h, after which the ampules were opened,
and the product was precipitated with methanol,
washed with methanol, and vacuum-dried at 40 C.
the cyclopropane ring directly bonded to the carbonyl
group and apparently conjugated with the vinylphenyl
group. Therefore, the FVPC molecule can be consid-
ered a common conjugated system.
O
H
CH CH C
CH2
The presence of strongly absorbing
groups in polymer macromolecules prepared from
FVPC monomer makes these polymers suitable as
a photosensitive base for photoresists. The two reac-
tive groups in the pendant chains, cyclopropane and
aldehyde, readily cleavable under irradiation, make
the polymers highly sensitive to UV irradiation. Under
UV irradiation, the polymers fairly readily transform
into the insoluble form.
The content of aldehyde groups in the copolymer
was determined by titration. A 0.2 0.3-g portion of
the copolymer was dissolved in 10 15 ml of dimeth-
ylformamide. After the dissolution was complete,
a 15-fold excess (by weight) of hydroxylamine hydro-
chloride in dimethylformamide was added. The mix-
ture was allowed to stand for 2 h at room temperature.
Then, 50 ml of distilled water was added. The pre-
cipitate was filtered off and washed once more on
the filter with 50 ml of distilled water. Then, 0.8 ml
of a 1% solution of Bromophenol Blue was added,
and the solution was titrated with 0.1 N NaOH until
the color became blue-green.
The decrease in the sensitivity of the absorption
bands belonging to the cyclopropane and aldehyde
groups in the initial steps of UV irradiation is insig-
nificant. Upon longer UV irradiation (30 min), these
absorption bands fully disappear. This fact indicates
that the cyclopropane and aldehyde groups are in-
volved in photochemical reactions apparently resulting
in the photochemical cross-linking of the polymer.
Photochemical cross-linking of the polymers was
studied as described in [7].
Experiments showed that the presence of a three-
membered ring and an aldehyde group, capable of
opening and cross-linking under UV irradiation
[13, 14], in the pendant chains of the polymers allows
preparation of negative photoresists. The photosensi-
tivity of the homopolymer prepared from FVPC is
The molecular weight of the homo- and copoly-
mers was estimated from their intrinsic viscosity
determined in benzene in an Ubbelohde viscometer at
20 C; for the homopolymer, [ ] = 1.03 dl g , and
the values for the copolymer are listed in the table.
1
1
56 cm2 J . As for the photosensitivity of the copoly-
The IR spectra of the synthesized monomer and its
homo- and copolymers were measured on a UR-20
mers obtained, it depends on the copolymer composi-
tion and increases with the mole fraction of FVPC
(see figure).
1
spectrometer, and the H NMR spectra, on a Tesla
BS-487B spectrometer (80 MHz) in CCl4. The pu-
rity of the compounds was determined by GLC on
an LKhM-8MD chromatograph, model 3.
Also, it is possible to prepare from the polymers
synthesized thin uniform coatings with low defec-
tiveness and good adhesion to the support.
CONCLUSION
The polymers synthesized also open up wide pros-
pects for chemical transformations of the aldehyde
groups by reactions with, e.g., phenylhydrazine, hy-
A new monomer, 2-formyl-1-(p-vinylphenyl)cyclo-
propane, its homopolymer, and copolymer with sty-
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 81 No. 4 2008

SYNTHESIS OF 2-FORMYL-1-(p-VINYLPHENYL)CYCLOPROPANE AND ITS POLYMERIZATION 675
rene were prepared. The compounds show high photo-
sensitivity due to the presence of cyclopropane and
aldehyde groups in the macromolecule.
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9. Sasaki, T., Eguchi, S., Ohno, M., and Umemura, T.,
J. Org. Chem., 1973, vol. 38, pp. 4095 4100.
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