Synthesis and properties of cyclopropane-containing optically transparent polymers

Article abstract of DOI:10.1134/S1070427210110248

New cyclopropane-containing optically transparent polymers were prepared by radical homopolymerization of p-(2-methoxycarbonylcyclopropyl)styrene and by its binary copolymerization with styrene and methyl methacrylate. The composition and structure of the

Full text of DOI:10.1134/S1070427210110248

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2010, Vol. 83, No. 11, pp. 2020−2023. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © K.G. Guliev, S.B. Mamedli, A.M. Guliev, 2010, published in Zhurnal Prikladnoi Khimii, 2010, Vol. 83, No. 11, pp. 1889−1893.
MACROMOLECULAR COMPOUNDS
AND POLYMERIC MATERIALS
Synthesis and Properties of Cyclopropane-Containing Optically
Transparent Polymers
K. G. Guliev, S. B. Mamedli, and A. M. Guliev
Institute of Polymeric Materials, National Academy of Sciences of Azerbaijan, Sumgait, Azerbaijan
Received March 1, 2010
Abstract—New cyclopropane-containing optically transparent polymers were prepared by radical
homopolymerization of p-(2-methoxycarbonylcyclopropyl)styrene and by its binary copolymerization with styrene
and methyl methacrylate. The composition and structure of these macromolecular compounds were determined,
and their main service characteristics were evaluated.
DOI: 10.1134/S1070427210110248
Optically transparent materials used today include
inorganic glasses, single and polycrystals, and polymers
[1–6].Themostwidelyusedareinorganicglassesbecause
of excellent optical characteristics. At the same time,
inorganic glasses are characterized by relatively high
density, difficult coloring and processing, and low shock
resistance. Therefore, in the past years organic polymers
found wide use as optically transparent materials for
optical devices and for decoration and finishing. Parts
and devices made using optically transparent polymers
are characterized by low weight, no acute fragments are
formed upon their break, and process for production of
optical parts from them is relatively simple and cheap.
Here we report on the synthesis and study of new
cyclopropane-containing polymers and copolymers:
homopolymers of p-(2-methoxycarbonylcyclopropyl)
styrene (MCPS) and its copolymers with methyl
methacrylate (MMA) and styrene (St). The efficiency of
using this class of compounds as optically transparent
material was demonstrated previously [7].
MCPS was prepared by the reaction of methyl
diazoacetate with p-divinylbenzene in the presence of
a catalytic amount of anhydrous СuSO4 as follows:
CH=CH2
The most widely used optically transparent polymers
are poly(methyl methacrylate) (PMMA), polystyrene
(PS), styrene copolymers, and polycarbonates. They
form the base of optically transparent polymers owing
to high light transmittance. However, each of these
polymers has certain drawbacks restricting its wide use.
For example, PMMA and PS have low softening point;
PMMA exhibit excellent transparency and high strength
characteristics, but its water absorption is high and the
surface of parts made on the PMMA base is readily
scratched; PS is less transparent than PMMA but is
characterized by good strength and low water absorption
coefficient. Hence, it is necessary to develop polymeric
materials combining the advantages of polystyrene and
poly(methyl methacrylate).
CH=CH2
Ha
Hb
Hc
C
C
+N2CHCO2CH3
O
C
OCH3
The structure of MCPS was determined by IR and 1H
NMR spectroscopy. In the IR spectrum of MCPS, there
is an absorption band at 1035–1045 cm–1, characteristic
2020

SYNTHESIS AND PROPERTIES OF CYCLOPROPANE-CONTAINING POLYMERS
2021
of a three-membered carbon ring; the band at 1630–
1635 cm–1 confirms the presence of the vinyl bond. In
addition, the IR spectrum of MCPS contains a strong
absorption band with a maximum at 1720 cm–1,
corresponding to stretching vibrations of the carbonyl
group. The band at 1105–1110 cm–1 is characteristic of
the ester bond. The structure of the synthesized MCPS is
also confirmed by 1H NMR spectroscopy: The 1H NMR
spectrum contains signals from vinyl protons НA at δ =
6.78 ppm, НB at δ = 5.39 ppm, and НC at δ = 5.82 ppm;
the signals of aromatic ring protons are manifested in
the range δ = 6.60–7.30 ppm, and the protons of the
cyclopropane ring, at δ = 0.65–1.68 ppm.
compositions of the polymers obtained and MCPS are
practically identical. The IR spectrum of the polymer
contains no bands characteristic of vinyl group, and in
the range 1035–1045 and 1720 cm–1 there are absorption
bands of the cyclopropane ring and carbonyl group,
respectively. The relative intensity of these absorption
bands does not noticeably change in going from the
monomer to the polymer. Thus, radical polymerization
of MCPS involves opening of only the double bond of
the vinyl group, with the cyclopropane ring remaining
intact. This fact is also confirmed by the 1H NMR data.
The 1H NMR spectrum of the polymer contains signals
at δ = 6.6–7.30 and δ = 0.65–1.68 ppm, characteristic of
the benzene and cyclopropane rings, respectively.
It should be noted that the signals of the vinyl
protons (НA, НB, НC) are shifted downfield relative to
styrene (НA, 6.4; НB, 5.10; НC, 5.58 ppm). This fact
can be accounted for mainly by the mesomeric effect
exerted by the substituent and by specific distribution
of the electron density in the cyclopropane ring, i.e.,
by formation of a common polyconjugation system
consisting of vinyl, phenylene, and cyclopropyl groups.
Apparently, the electron-withdrawing ester group
СООСН3 is also involved in this polyconjugation
system, causing downfield shift of the vinyl proton
signals [8–10].
The IR spectra of the polymers contain absorption
bands characteristic of stretching vibrations of the
benzene ring (1450–1500, 1570–1600 cm–1), bending
vibrations of the 1,4-disubstituted benzene ring (1010
and 1110 cm–1), and out-of-plane bending vibrations of
two adjacent aromatic CH groups (830–835 cm–1).
TakingintoaccountthecapabilityofMCPSforradical
polymerization with double bond opening, with the aim
to prepare new cyclopropane-containing copolymers
and to reveal specific features of MCPS behavior under
the conditions of radical copolymerization, we studied
the binary copolymerization of MCPS with styrene and
methyl methacrylate (AIBN initiator, 0.5 wt % relative
to comonomers, solvent benzene, 70°C). The copolymer
compositions and calculated copolymerization constants
for MCPS and comonomers (St, MMA) are given in
Table 1.
Because MCPS is a polyfunctional compound,
its radical homopolymerization or copolymerization
should be expected to yield new reactive polyfunctional
homo- and copolymers. The MCPS polymerization was
performed in the presence of AIBN in the bulk and in
benzene solution at 70°C. The polymers obtained, after
appropriate purification and drying, were white soluble
powders. The results of studying the composition
and structure of the polymers showed that the MCPS
polymerization followed the scheme
As seen from Table 1, in radical copolymerization
MCPS is a more active monomer than styrene or methyl
methacrylate. The observed relatively high activity
of MCPS in radical copolymerization is due to the
presence in its molecule of an electron-withdrawing
ester group involved in the common conjugation chain,
which increases the level of conjugation in the MCPS
molecule. It is known that the mutual polarizability
of the monomer molecule and active radical center
in the transition state plays an important role in
polymerization. In our case, the electron-withdrawing
ester group causes redistribution of the electron density
both in the monomer and in the radical center formed
from it. As a result, the energy required for the formation
of the transition state decreases, and both the monomer
reactivity and the polymerization rate increase.
CH
H2C
C6H4
n
COOCH3
H2C
CH
C6H4
70°C, AIBN
n
COOCH3
It follows from Table 2 that cyclopropane-containing
The analytical data show that the elemental
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 83 No. 11 2010

2022
GULIEV et al.
Table 1. Copolymerization conditions and properties of MCPS copolymers with styrene and methyl methacrylate
Composition of initial
Copolymer composition, mol %
monomer mixture, mol %
Conversion,
g1
g2
Q1
е1
%
MCPS
~ MCPS ~ ~ MMA ~
~St~
m2
MMA
St
М1
m1
m2
80
70
50
30
20
20
30
50
70
80
–
–
–
–
–
6.0
85.61
78.63
64.29
48.19
37.88
14.39
21.37
35.71
51.81
62.12
–
–
–
–
–
8.0
10.0
5.0
1.35 ± 0.04 0.3 ± 0.02
1.46
–0.55
–1.6
7.0
80
70
50
30
20
–
–
–
–
–
20
30
50
70
80
8.0
7.8
9.6
11.2
8.2
84.35
76.75
61.24
43.52
32.89
–
–
–
–
–
15.65
23.25
38.76
56.48
67.11
1.24 ± 0.03 0.42 ± 0.025 4.46
Table 2. Characteristics of polymers obtained
MCPS a +
MMA
Parameter
MCPS a + St
MCPS
1.20
St
MMA
Density, g cm–3
1.07
1.5870
130
1.05
1.5790
123
1.07
1.18
Refractive index, nD20
1.5970
138
22.5
1.590
1.4917
Vicat softening point, °C
Brinell hardness, kg mm–2
Specific impact resilience, kg cm cm–2
Ultimate tensile strength, MPa
Relative elongation, %
103
115
21.8
18.0
50.0
1.9
19.0
18.8
50.7
3.5
14
13
21.0
52.0
3.8
18
12
39.0
1.7
–
60.0
2.1
–
Adhesion strength, MPa
Water absorption in 24 h, %
4.80
0.08
5.85
0.12
8.85
0.06
0.1
0.3
a MCPS content in copolymers 20 mol %.
polymers and copolymers exhibit better thermal and
physicomechanical properties compared to polystyrene,
which allows them to be used in production of optical
parts and contact lenses.
The transparency (light transmission in the visible
range) of poly-MCPS is 90–96% and only slightly
depends on the sample thickness (up to 6–8 mm). At
relatively large thickness, the optical properties get
worse, which is typical of all the known transparent
polymers. With respect to moisture resistance, MCPS-
based polymers are not inferior to polystyrene and
styrene–methyl methacrylate copolymer.
Our results show that MCPS polymers and
copolymers exhibit, along with high physicomechanical
characteristics, also good optical properties. Poly-MCPS
remains transparent up to 100°С at 2-h heat treatment.
Evaluation of the physicomechanical properties of poly-
MCPS in the temperature interval from 80 to –20°C
showed that at these temperatures it preserves high
tensile strength, and at low temperatures its elasticity
does not decrease noticeably.
High-quality optical items can be prepared from
MCPS polymers and copolymers by pressing, extrusion,
and pressure casting.
Thus, introduction of p-substituents
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 83 No. 11 2010

SYNTHESIS AND PROPERTIES OF CYCLOPROPANE-CONTAINING POLYMERS
2023
carbonylcyclopropyl)styrene, was synthesized, and its
radicalhomopolymerizationandbinarycopolymerization
with styrene and methyl methacrylate were performed.
New polyfunctional cyclopropane-containing optically
transparent polymers were prepared.
CH
CH COOCH3
CH2
into the aromatic ring improves the optical, thermal, ad-
hesion, and physicomechanical properties of the target
polymers and allows preparation of shockproof transpar-
ent polymeric materials with high optical characteristics.
(2) The composition and structure of the synthesized
polymers were determined, and the copolymerization
parameters were found. p-(2-Methoxycarbonylcyclo-
propyl)styrene is more active than styrene and methyl
methacrylate in radical copolymerization.
EXPERIMENTAL
p-(2-Methoxycarbonylcyclopropyl)styrene was pre-
pared as follows. To a solution of 0.3 mol of p-divinyl-
benzene inbenzene containing0.1 gofanhydrousСuSО4
we added dropwise a solution of 0.1 mol of methyl dia-
zoacetate in benzene. After the reaction completion, the
solvent and excess divinylbenzene were distilled off,
and the target product was isolated by vacuum distil-
lation. Yield 18.38 g (91%); bp 108–110°С/1 mm Hg,
(3) The synthesized polymers and copolymers
surpass in their main service characteristics polystyrene
and poly(methyl methacrylate) and exhibit optical
transparency, which allows their use in production of
optical parts.
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d420 1.1236 g cm–3, nD 1.5800. Analytical data: Found,
20
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1
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RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 83 No. 11 2010