Synthesis and properties of fluorosilicon compounds for protection of cultural monuments from harmful environmental exposure

Article abstract of DOI:10.1007/s11172-014-0467-0

Methods for the synthesis of perfluorocarboxylic acid derivatives with reactive trialkoxysilyl groups soluble in organic and organofluorine (1,1,2-trichlorotrif1uoroethane, etc.) solvents have been developed. The contact angles of water and decalin, water absorption, resistance to freezing, and salt-resistance of limestone and plaster samples treated with these compounds were determined. Fluorosilicon organic compounds impart more hydro- and oleophobic properties to the protected surfaces than known organosilicon agents and reliably protect sculptures and architectural monuments from mold and algae deposition.

Full text of DOI:10.1007/s11172-014-0467-0

546
Russian Chemical Bulletin, International Edition, Vol. 63, No. 2, pp. 546—548, February, 2014
Synthesis and properties of fluorosilicon compounds for protection
of cultural monuments from harmful environmental exposure*
A. A. Yarosh,a S. P. Krukovsky, A. M. Sakharov, M. Yu. Popovich, V. M. Kotov, and T. A. Pryakhina
a
a
a
b
b
a
N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,
4
7 Leninsky prosp., 119991 Moscow, Russian Federation.
Fax: +7 (499) 135 5328. Eꢀmail: yar@ioc.ac.ru
b
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
8 ul. Vavilova, 119991 Moscow, Russian Federation.
2
Fax: +7 (499) 135 5085. Eꢀmail: kotov@ineos.ac.ru
Methods for the synthesis of perfluorocarboxylic acid derivatives with reactive trialkoxysilyl
groups soluble in organic and organofluorine (1,1,2ꢀtrichlorotrif1uoroethane, etc.) solvents
have been developed. The contact angles of water and decalin, water absorption, resistance to
freezing, and saltꢀresistance of limestone and plaster samples treated with these compounds
were determined. Fluorosilicon organic compounds impart more hydroꢀ and oleophobic propꢀ
erties to the protected surfaces than known organosilicon agents and reliably protect sculptures
and architectural monuments from mold and algae deposition.
Key words: synthesis, fluorosilicon organic compounds, hydrophobization, oleophobizaꢀ
tion, contact angles, resistance to freezing, salt resistance.
Cultural monuments are most often protected from
dioxanonanoyl fluoride 2 (hexafluoropropylene oxide triꢀ
mer) with ethanol gave ester 3, which then reacted with
harmful environmental exposure using formulations based
on organosilicon compounds, which impart waterꢀrepelꢀ
lent properties to the protected surfaces. However, these
coatings have no oleophobic properties, because they swell
or are partially soluble in organic compounds, which apꢀ
pear in the atmosphere due to automotive exhausts and
other manꢀmade factors. Perfluorinated organic comꢀ
pounds have very low surface tension, they are poorly solꢀ
uble in organic solvents, and have higher hydroꢀ and oleꢀ
ophobic properties than organosilicon compositions.
A drawback of perfluorinated compounds is that, unlike
functional organosilicon compounds, they most often do
not react with Group 2 metal oxycarbonates present on
the surface of structural materials.
1
—3
ꢀaminopropyltriethoxysilane
pound 1 (Scheme 1).
to give the target comꢀ
Scheme 1
F
R = C F OCF(CF )CF OCF(CF )
3
7
3
2
3
The purpose of this study is development of methods
for the synthesis of compounds containing both organoꢀ
silicon and organofluorine moieties. These compounds are
able to be firmly attached to the surface of constructional
materials through the organosilicon moiety containing triꢀ
alkoxysilyl groups, while the organofluorine moiety proꢀ
vides hydroꢀ and oleophobic protection of the item.
The synthesis of perfluoroꢀ2,5ꢀdimethylꢀ3,6ꢀdioxꢀ
anonanoic ꢀtriethoxysilylpropylamide 1 was performed
in two steps. The reaction of perfluoroꢀ2,5ꢀdimethylꢀ3,6ꢀ
The completion of the reactions was checked by IR
spectroscopy. Successive disappearance of the absorption
–
1
–1
bands at 1870 cm (acyl fluoride C=O) and 1780 cm
ester C=O) and appearance of a band at 1740 cm–1 (amide
(
C=O) were observed. The yield of compound 1 was 70%
1
in relation to the starting acyl fluoride. The H and
19
F NMR spectra confirm the structures of the products
(
see Experimental).
Treatment of samples of constructional materials was
performed by immersion into 5% solutions of amide 1 in
Freonꢀ113 or ethyl acetate. The efficiency of the formed
organofluorosilicon coating was estimated from the conꢀ
tact angles of water and decalin and the sample resistance
*
On the occasion of the 80th anniversary of the N. D. Zelinsky
Institute of Organic Chemistry of the Russian Academy of
Sciences.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 0546—0548, February, 2014.
066ꢀ5285/14/6302ꢀ0546 © 2014 Springer Science+Business Media, Inc.
1

Protection of cultural monuments
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 2, February, 2014
547
to freezing, salt resistance, steam tightness, and water
absorption. The organosilicon liquid GKZhꢀ94 (reꢀ
search and production company PENTA, Russia) and the
organosilicon product Disboxanꢀ450 (Lacufa, Germany),
which were applied on limestone samples in a similar way,
served as the reference samples. The water, freezing,
and salt resistances of the samples hydrophobized by
compound 1 were determined according to the proceꢀ
dures NORMAL, RILEM 11.8a, RILEM 11.8b, GOST
A similar situation was also observed in the salt resistance
testing of the samples. The salt resistance of constructionꢀ
al materials is defined as the ability to withstand repeated
immersion of samples into a 14% solution of sodium sulfꢀ
ate at room temperature for 2 h followed by drying at 60.
The reference samples started to be intensively deterioratꢀ
ed after three testing cycles, while samples treated with
compound 1 were destroyed only after 27—28 cycles. The
samples treated with the Disboxanꢀ450 product were alꢀ
ready destroyed after 15 cycles of similar salt resistance
testing.
7
025ꢀ67, and GOST 2309ꢀ80 and other procedures used
4
,5
by restorers.
The application of hydrophobic coatings on construcꢀ
tional materials gives rise to a surface protective layer,
which prevents penetration of condensed moisture inside.
This coating can partially prevent removal of the evapoꢀ
rated water from the material; therefore, steam tightness
of the hydrophobized and untreated samples were comꢀ
pared. The steam tightness was measured in accordance
with GOST 25898ꢀ83. A decrease in the steam tightness
of plaster samples hydrophobized by compound 1 was
The biological stability was assessed in collaboration
with employees of the State Research Institute of Restoraꢀ
tion using a sixꢀpoint score. The biological stability of
treated limestone samples 58 days after they were infected
by microflora (see Experimental) corresponded to 1 or 2
two points, i.e., although compound 1 does not exhibit
fungicidal properties, it is not digested or is poorly digestꢀ
ed by fungi. Hence, the compound can be recommended
for longꢀterm protection of constructional materials from
infestation by molds, fungi, and algae. Together with emꢀ
ployees of the State Research Institute of Restoration and
the Central Scientific Restoration and Design Workshop
(Moscow), a number of cultural monuments were treated
with the developed agent, in particular, some graveꢀstones
in the Donskoy Monastery and Novodevichy Convent,
whitestone graves of Symeon of Polotsk and the dukes Ilya
and Ivan Suleshovs from the collection of the Moscow
State Integrated MuseumꢀReserve Kolomenskoye and
some other. The field tests demonstrated that algae and
fungi do not grow on the protected pieces of art even 8 years
after their treatment.
5
.14%, which complies with the requirements imposed on
hydrophobizing coatings.
Water absorption of hydrophobized samples of brickꢀ
rubble plaster. The hydrophobic effect was calculated as
the ratio of the difference of water absorption between the
initial and treated samples after they have been kept in
water for 8 h (Table 1).
Determination of the resistance to freezing, salt resisꢀ
tance, and biological stability of hydrophobized samples of
brickꢀrubble plaster. By resistance to freezing is meant the
ability of the waterꢀsaturated material to withstand reꢀ
peated alternative freezing in air and thawing in water.
Water that freezes in the pores of the constructional mateꢀ
rial destroys the material. It was found that even after 90
freezing—thawing cycles, the lime wash did not drop off
from plaster samples treated with 5% solutions of comꢀ
pound 1, whereas the reference samples already lost the
staining after two cycles and were destroyed after 15 cycles.
Several waterꢀemulsion compositions based on comꢀ
pound 1 were formulated. They contained hexane, ocꢀ
tane, butanol, and xylene as the organic phase and oxyꢀ
6
ethylated isononylphenols or perfluorocarboxylic acid
7
C F O[CF(CF )CF O] CF(CF )COOH prepared by
3
7
3
2
2
3
hydrolysis of hexafluoropropylene oxide tetramer as the
surfactant. The application of these compositions on strucꢀ
tural materials gives rise to the same hydrophobic effect as
the use of solutions of compound 1.
Table 1. Water absorption, hydrophobic effect, and contact anꢀ
gles () of water and decalin for limestone samples pretreated
with 5% solutions of hydrophobizing agents
Experimental
1H and 19F NMR spectra were recorded on a Bruker 300SF
spectrometer (operating at 300.13 and 282.40 MHz, respectiveꢀ
ly). IR spectra were measured on a Bruker AlphaꢀT spectromeꢀ
ter. The highꢀresolution electrospray ionization (ESI) mass specꢀ
trum was run on a Bruker micrOTOF II instrument. The meaꢀ
surements were carried out in the positive ion mode (capillary
voltage of 4500 V). The range of mass scanning m/z was 50 to
Hydrophoꢀ
bic effect
Water
absorption (%)
Hydrophoꢀ
bic effect
/deg
Water Decalin
2
h
8 h 24 h
Reference* 6.34 6.62 6.96
GKZhꢀ94 0.39 1.36 1.83
Disbꢀ
oxanꢀ450
Comꢀ
pound 1
0
0
98
120
0
51
54
79.45
69.79
0.25 2.00
—
3
000 D, the calibration was both external and internal (Electroꢀ
spray Calibrant Solution, Fluka). Samples were injected by
0.18 0.38 1.38
94.26
138
115
–
1
a syringe as acertonitrile solutions, the flow rate was 3 L min
,
nitrogen served as the nebulizer gas (4 L min– ), and the interꢀ
1
*
The sample untreated with the hydrophobizing agent.
face temperature was 180 C.

548
Russ.Chem.Bull., Int.Ed., Vol. 63, No. 2, February, 2014
Yarosh et al.
Perfluoroꢀ2,5ꢀdimethylꢀ3,6ꢀdioxanonanoyl fluoride (2) was
prepared by a known procedure by polymerization of hexafluoꢀ
ropropylene oxide in the presence of CsF in diglyme.
Ethyl perfluoroꢀ2,5ꢀdimethylꢀ3,6ꢀdioxanonanoic acid (3).
Compound 2 (27.9 g, 56 mmol) was placed into a flask equipped
with a stirrer, a reflux condenser, a thermometer, and a dropping
funnel, and ethanol (2.2 g, 58 mmol) was added with stirring.
The reaction mixture was heated for 2 h at 50 C, washed with a
at –20 C, then immersed again into water for thawing and
weighed. The testing results are given above.
8
Biological stability was estimated at the State Research Instiꢀ
tute of Restoration. The limestone samples with dimensions
551 cm pretreated with 5% solutions of compound 1 in Freonꢀ
113 or ethyl acetate and reference samples were infected with
a suspension of the fungal spores Ulocladium sp., Aspargillus verꢀ
sicolor, and Aspargillus niger. The infected samples were placed
in a dessicator with the bottom covered with water and kept in
a thermostat at 27 C and a relative air humidity of 90%. The
development of the fungi on the samples was monitored by
a MBSꢀ9 microscope. After 58 days, the reference limestone samꢀ
ples were completely covered by the branched mycelium, while
only limited spore growth was noted on the treated samples.
According to GOST 9.048ꢀ89, these results correspond to resisꢀ
tance of 1—2 points.
5
% solution of sodium carbonate, dried with calcined MgSO4,
and distilled. This gave ester 3 in a 80% yield, b.p. 165 C.
1
H NMR (DMSOꢀd , ): 1.53 (t, 3 H, Me, J = 6.0 Hz); 4.64—4.57
6
19
(
(
(
q, 2 H, OCH , J = 6.0 Hz). F NMR (CFCl , ): –(80—83)
2
3
m, 9 F, CF ); –(85—86) (m, 4 F, CF O); –(132.7—133.4)
3
2
m, 2 F, CF ); –134.6 (q, 1 F, OCF(CF )C=O); –144 (t, 1 F,
2
3
CF(CF )CF O). Found (%): C, 25.11; H, 0.97; F, 61.53.
3
2
C H F O . Calculated (%): C, 25.19; H, 0.95; F, 61.64.
1
1
5
17
4
Perfluoroꢀ2,5ꢀdimethylꢀ3,6ꢀdioxanonanoic ꢀtriethoxysilylꢀ
propylamide (1). ꢀAminopropyltriethoxysilane (b.p. 79—80 C
3 Torr), research and production company PENTA) (11 g,
0 mmol) was added with stirring at room temperature to comꢀ
References
(
5
1
. S. P. Krukovsky, A. A. Yarosh, A. A. Glazkov, D. V. Batizat,
T. N. Redina, J. Fluorine Chem., 1999, 96, 31.
2. RF Pat. 2149151; Byull. izobret. [Bull. of Inventions], 2000,
pound 3 (25.6 g, 50 mmol). The mixture was stirred for 2 h, and
the product was isolated by vacuum distillation. The yield of
1
compound 1 was 90—95%, b.p. 121—123 C (1 Torr). H NMR
No. 14; www.1fips.ru.
(
DMSOꢀd , , J/Hz): 0.77 (t, 2 H, CH Si, J = 7.0 Hz); 1.34—1.29
6
2
3
. RF Pat. 2151151; Byull. izobret. [Bull. of Inventions], 2000,
(
t, 9 H, 3 Me, J = 6.0 Hz); 1.97—1.92 (m, 2 H, CH CH CH ,
2
2
2
No. 17; www.1fips.ru.
J = 6.0 Hz); 3.51—3.46 (q, 6 H, OCH CH , J = 6.0 Hz); 8.23
2
3
19
4. A. A. Yarosh, S. P. Krukovsky, B. G. Zavin, V. M. Kotov,
T. N. Pryakhina, V. N. Yarosh, 10 Vseross. konf. "Kremniiorꢀ
ganicheskie soedineniya: sintez, svoistva, primenenie" [Orgaꢀ
nosilicon Compounds. Synthesis, Structure, Applications],
(Moscow, May 26—30, 2005), Abstrs., Moscow, 2005, 3S23.
(
s, 1 H, HN). F NMR (CFCl , ): –(80—83) (m, 9 F, CF );
3
3
–
–
(85—86) (m, 4 F, CF O); –(132.7—133.4) (m, 2 F, CF );
2 2
134.6 (q, 1 F, OCF(CF )C=O); –144 (m, 1 F, OCF(CF )CF O).
3
3
2
MS (ESI): m/z 722.0838; calculated for C18H22F17NO Si,
6
+
[
M + Na] : m/z 722.0837. Found (%): C, 30.78; H, 3.23; N, 1.97;
5
. A. A. Yarosh, S. P. Krukovsky, T. A. Pryakhina, V. M. Koꢀ
tov, B. G. Zavin, A. M. Sakharov, Mendeleev Commun., 2006,
F, 45.98; Si, 3.62. C H NF SiO . Calculated (%): C, 30.90;
18
22
17
6
H, 3.15; N, 2.0; F, 46.21; Si, 4.0.
1
6, 190.
Testing procedure. Cylindrical brickꢀrubble plaster samples
6
7
8
. RF Patent 2327674; Byull. izobret. [Bull. of Inventions], 2008,
No. 18; www.1fips.ru.
. RF Pat. 2370476; Byull. izobret. [Bull. of Inventions], 2009,
No. 29; www.1fips.ru.
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www.patft.uspto.gov.
(
3 cm in diameter and 5 cm long) were immersed for 1 min in 5%
solutions of compound 1 in Freonꢀ113 or ethyl acetate. The
samples were dried to a constant weight.
Water absorption. The samples were placed in water for 2, 8,
and 24 h and then weighed (GOST 2309ꢀ80). The results are
given in Table 1.
Resistance to freezing. The testing was performed in accorꢀ
dance with GOST 7025ꢀ67. The samples were placed in water
for 2 h, then placed into a freezing chamber and kept for 2 h
Received November 28, 2013;
in revised form January 29, 2014