Sodiumoxy(aminopropyl)alkoxysilanes - AB2 type monomers for the synthesis of hyperbranched poly(aminopropyl)alkoxysiloxanes and their derivatives

Article abstract of DOI:10.1016/j.jorganchem.2017.11.028

Based on commercially available aminopropyltrialkoxysilanes, new monosodium salts of organoalkoxysilanes (sodiumoxoaminopropyldialkoxysilanes) with two types of chemically independent functional -ONa and -OAlk groups at the silicon atom were synthesized and characterized. The sodiumoxoaminopropyldialkoxysilanes obtained can be regarded as AB₂-type monomers - promising reagents for providing controlled polycondensation and production of functional organosilicon polymers with controlled molecular architectures. Subsequently, polyaminopropylsiloxanes with hyperbranched molecular architectures were obtained by heterofunctional polycondensation of the corresponding AB₂-type monosodiumoxoorganodialkoxysilanes. The structures synthesized were characterized using ²⁹Si NMR, ¹H NMR, GPC and elemental analyses. The hyperbranched polymer matrices obtained containing aminopropyl organic radicals showed the ability to stabilize silver nanoparticles.

Full text of DOI:10.1016/j.jorganchem.2017.11.028

Accepted Manuscript
Sodiumoxy(aminopropyl)alkoxysilanes - AB2 type monomers for the synthesis of
hyperbranched poly(aminopropyl)alkoxysiloxanes and their derivatives
Dmitry Migulin, Sergey Milenin, Georgy Cherkaev, Evgeniya Svidchenko, Nikolay
Surin, Aziz Muzafarov
PII:
S0022-328X(17)30677-0
10.1016/j.jorganchem.2017.11.028
JOM 20193
DOI:
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 12 September 2017
Revised Date: 19 November 2017
Accepted Date: 30 November 2017
Please cite this article as: D. Migulin, S. Milenin, G. Cherkaev, E. Svidchenko, N. Surin, A. Muzafarov,
Sodiumoxy(aminopropyl)alkoxysilanes - AB2 type monomers for the synthesis of hyperbranched
poly(aminopropyl)alkoxysiloxanes and their derivatives, Journal of Organometallic Chemistry (2018), doi:
10.1016/j.jorganchem.2017.11.028.
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ACCEPTED MANUSCRIPT
Sodiumoxy(aminopropyl)alkoxysilanes - AB2 type monomers for the synthesis
of hyperbranched poly(aminopropyl)alkoxysiloxanes and their derivatives
Dmitry Migulin1, Sergey Milenin1, Georgy Cherkaev1, Evgeniya Svidchenko1, Nikolay
Surin1, Aziz Muzafarov1,2
1N.S. Enikolopov Institute of Synthetic Polymer Materials, Russian Academy of Science, 117393
Moscow, Profsoyuznaya st. 70, Russia
2A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Science, 119991
Moscow, Vavilova st. 28, Russia
E-mail : aziz@ispm.ru
Abstract
Based on commercially available aminopropyltrialkoxysilanes, new monosodium salts of
organoalkoxysilanes (sodiumoxoaminopropyldialkoxysilanes) with two types of chemically
independent functional -ONa and -OAlk groups at the silicon atom were synthesized and
characterized. The sodiumoxoaminopropyldialkoxysilanes obtained can be regarded as AB2-
type monomers - promising reagents for providing controlled polycondensation and production
of functional organosilicon polymers with controlled molecular architectures. Subsequently,
polyaminopropylsiloxanes with hyperbranched molecular architectures were obtained by
heterofunctional
polycondensation
of
the
corresponding
AB2-type
monosodiumoxoorganodialkoxysilanes. The structures synthesized were characterized using
29Si NMR, 1H NMR, GPC and elemental analyses. The hyperbranched polymer matrices obtained
containing aminopropyl organic radicals showed the ability to stabilize silver nanoparticles.
Keywords
Aminopropyltrialkoxysilane;
Sodiumoxoaminopropyldialkoxysilane;
Hyperbranched,
Heterofunctional polycondensation; AB2-type monomer.
1.
Introduction
The majority of methods for the synthesis of polysiloxane compounds provide a statistical
distribution of products, both in structure and composition. Therefore, from the perspective of
the basic "structure-properties" relationship paradigm in polymer chemistry, the development
of selective methods that allow the molecular structures of the polymers formed to be
controlled is a very important task. The following synthetic approaches that allow synthesizing
siloxane polymers with controlled structures can be noted: non-equilibrium polymerization [1],
heterofunctional condensation reactions [2, 3], exchange decomposition reactions [4] and the
Pierce-Rubinstein reaction [5] which has become very popular and has led to the synthesis of a
significant number of well-defined structures. Furthermore, the use of monosodium salts of
alkoxysilanes (sodiumoxyalkoxysilanes) also known as Rebrov salts became one of the simplest
versatile ways to obtain siloxane structures with controlled molecular architecture [6]. Over the
past quarter century, many such siloxane structures have been synthesized with the use of
monosodiumoxoalkoxysilanes [7]. The other compounds that should be mentioned include
branched
oligosiloxanes
and
polyorganosiloxanedendrimers
[8],

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hyperbranchedpolyethoxysiloxanes [2, 3], linear polyorganosilsesquioxanes [9], as well as
unique forms of polyorganosilsesquioxanes [10].
The known methods for the preparation of monosodiumoxoalkoxysilanes include the synthesis
from the corresponding alkoxysilanes in reactions with alkali metals [11]. The multistage nature
of this process due to the need for isolation of the corresponding organoalkoxysilanol, as well
as the usage of unstable alkali metals in these reactions make this method ineffective.
A much more facile one-step process for the production of monosodiumoxyalkoxysilanes is to
synthesize them from the corresponding alkoxysilanes in reactions with alkali metal hydroxides
(Fig. 1), [12, 13].
A method for synthesizing a number of monosodiumoxoorganoalkoxysilanes (Fig. 1) based on a
direct reaction of organoalkoxysilanes with sodium hydroxide was studied in detail and
optimized [6, 14].
Figure 1. Sodiumoxyorganoalkoxysilanes obtained in [6].
In fact, methods for the preparation of various sodiumoxoorganodialkoxysilanes have been
developed based on a number of organotrialkoxysilanes [6] (Fig. 1). Within the framework of
the Flory theory [15], sodiumoxoorganodialkoxysilanes can be considered as AB2-type
monomers that are promising reagents for controlled polycondensation and production of
polymers with controlled molecular architecture.
In turn, there are no studies on the characterization and preparation of monosodium salts
based on commercially available aminopropyltrialkoxysilanes (Fig. 2).
R
NH
OAlk
Si
OAlk
OAlk
R = -H, -CH2CH2NH2; Alk = -CH3, -CH2CH3
Figure 2. Commercially available aminopropylalkoxysilanes.

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In view of the fact that, due to the high coordination ability of the amino groups, amino-
containing polymer matrices are widely used in the development of agents for metal ion
coordination and stabilization of metal nanoparticles [16], adsorption of inorganic
nanoparticles [17], encapsulating agents for the transport of drug substances [18], and taking
into consideration the widespread use of aminopropylalkoxysilanes and aminopropyl-
containing polysiloxanes as binders and hardeners [19] in the manufacture of copolymeric
materials [20], special purpose coatings [21], water-soluble organosilicon systems [22], etc., the
development and creation of a new class of amino-containing organosilicon monomer and
polymer structures are promising tasks.
Thus, the purpose of this work was to expand the range of monosodium organoalkoxysilane
salts by development of synthetic methods for the production of new monosodium salts and
evaluation of the prospects of these compounds in the creation of new amino-containing
polyorganosiloxane structures with controlled molecular architecture.
In this work, commercially available aminopropyltrialkoxysilanes were employed to prepare
new mono-sodium salts of organoalkoxysilanes. Based on the latter, the corresponding
polyaminopropylsiloxanes with controlled hyperbranched structures were then synthesized.
The polymer matrices thus obtained were then used for the production and stabilization of
metallic silver nanoparticles.
2.
Experimental section
2.1 Materials
Starting reagents were purchased from Acros or Aldrich. All solvents were of reagent grade and
dried and distilled before use according to standard procedures.
2.2 Methods
NMR spectra in solutions were acquired using a Bruker Avance AV-300 spectrometer (300 MHz
for 1H; 77.5 MHz for 13C; 59.6 MHz for 29Si). Chemical shifts are reported in ppm and referred to
1
the residual non deuterated solvent frequencies (δ = 7.25 ppm) for Н NMR; deuterated
chloroform (δ = 77.00 ppm) for 13C NMR; tetramethylsilane (δ = 0.00 ppm) for 29Si NMR;
ammonia (δ = 0.00 ppm) for 15N NMR, sodium chloride (δ = 0.00 ppm) for 23Na NMR.
High resolution mass spectra were measured with a Bruker Microtof II instrument with
electrospray ionization (ESI) (Germany)
GLC analysis was performed on a Chromatech Analyst-5000 chromatograph (Russia) with a
сatharometer detector, helium as the carrier gas, and a 2 m x 3 mm column. The stationary
phase SE-30 (5%) was applied on Chromaton-H-AW.
GPC analysis was conducted in a chromatographic system consisting of a STAYER series II high-
pressure pump (Aquilon, Russia), a RIDK 102 refractive index detector (Czech Republic), and a

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JETSTREAM 2 PLUS column oven (KNAUER, Germany). The thermostating temperature was
40 °C (+ / -0.1 °C). Toluene was used as the eluent, and the flow rate was 1.0 ml/min. A 300 x
7.8 mm column was filled with Phenogel sorbent (Phenomenex, USA) with a particle size of 5
µm and a pore size of 103 Å (passport range separation of up to 75,000 D). Recording and data
counting were performed using a Multichrom 1.6 GPC program (Ampesand, Russia). Calibration
of GPC data was conducted by the Polysterene Standard Calibration Kit for Liphophilic GPC (E.
Merck, Darmstadt, F.R. Germany).
Ultraviolet absorption (UV) spectra of the samples (in methanol and acetonitrile solutions, in
cells with 1 cm light path) were recorded using a Shimadzu UV 2501 PC spectrophotometer.
DLS measurements for particle sizing were conducted with a Zetatrac dynamic light scattering
spectrometer (Microtrac, USA) using Microtrac V 10.5.3 software.
TEM analysis was provided with a JEM-1011 Transmission Electron Microscope (JEOL Ltd.,
Japan) equipped with a Gatan Erlangshen ES500W digital camera, using Digatal Micrograph v.3
software (Gatan) for the camera control and image processing.
2.3 Synthetic procedures
2.3.1 Trialkylsilanols
2.3.1.1 Synthesis of trimethylsilanol
200 ml of 0.1 M HCl solution was slowly added (in 1 hour) to hexamethyldisilazane (0.683 mol)
with stirring. The mixture was stirred at room temperature for 1 hour. GLC data showed the
absence of initial hexamethyldisilazane. The resulting solution was washed from the excess of
HCl acid and then dried with CaCl2. According to GLC data, the yield of the target compound
was 95 %.
2.3.1.2 Synthesis of vinyldimethylsilanol
Vinyldimethylchlorosilane (0.221 mol) was slowly added (in 1 hour) to a two-phase system
consisting of (NH4)2CO3 (0.132 mol) aqueous solution (100 ml) and diethyl ether (100 ml). The
mixture was stirred at room temperature for 3 hours. The resulting solution was extracted 3
times with 75 ml of diethyl ether and the combined extracts were washed with
a saturated aqueous NaCl solution and then dried with CaCl2. Diethyl ether was evaporated.
According to GLC data, the yield of the target compound was 60 %.
2.3.2 Monosodium salts of aminopropylalkoxysilanes
2.3.2.1Synthesis of monosodium salts of aminopropylalkoxysilanes
The typical procedure for the preparation of monosodium salts from the corresponding
aminopropylalkoxysilanes is shown in Scheme 1.

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A mixture of the corresponding aminopropyltrialkoxysilane (0.05 mol)) and sodium hydroxide
(0.05 mol) was stirred in boiling THF (40 ml) for 20 min under argon. After cooling, the resulting
solution was evaporated under reduced pressure and vacuumed at 1 mBar for 30 min at 50 °C.
Products were obtained as colorless liquids in quantitative yields.
(Product characterization for this and other reactions is given in supporting information).
2.3.2.2 Termination of monosodium salts of aminopropylalkoxysilanes with
trimethylchlorosilane
The procedure for the termination of the corresponding sodiumoxoaminopropylalkoxysilanes is
described in Scheme 2.
Trimethylchlorosilane (0.022 mol) in dry THF (5 ml) was added to a solution of the
corresponding sodiumoxoaminopropyldialkoxysilanes (0.022 mol) and pyridine (0.024 mol) in
dry THF (15 ml) at –30 ° C. The mixture was stirred overnight at room temperature. The solvent
was removed under reduced pressure, and the mixture was diluted with dry hexane and
filtered. Hexane was removed under reduced pressure, and the product was distilled under
vacuum (1 mBar). The product was obtained as colorless liquid in 80-90% yield.
2.3.3 Hyperbranched polyaminopropylalkoxysiloxanes
2.3.3.1 Synthesis of hyperbranched polyaminopropylalkoxysiloxanes
The typical procedure for the preparation of hyperbranched aminopropylalkoxysiloxanes is
presented in Scheme 4.
To a solution of the corresponding sodiumoxoaminopropylalkoxysilane obtained previously
(0.022 mol) with additionally 20 ml toluene, an equimolar amount of acetic acid (0.022 mol)
was rapidly added at room temperature. The solution was left overnight with stirring. Next day,
the resulting solution was centrifuged, decanted from the precipitate, evaporated under
reduced pressure and vacuumed at 1 mBar for 2 hours at 50 °C. The products were obtained as
colorless viscous liquids in quantitative yields.
2.3.3.2 Termination of amino groups in hyperbranched polyaminopropylalkoxysiloxanes with
phenyl isocyanate
The procedure for the termination hyperbranched polyaminopropylalkoxysiloxanes amino
groups is given in Scheme 6.
To the corresponding hyperbranched polyaminopropylalkoxysiloxane (2.3 mmol) dissolved in a
mixture of 10 ml THF and 5 ml toluene, phenyl isocyanate (2.4 mmol in the case of
polyaminopropylethoxysiloxane
or
4.7
mmol
in
the
case
of
polyethylenediaminopropylmethoxysiloxane) was added under argon at room temperature.
The solution was left overnight with stirring. Next day, the solvent was evaporated under
reduced pressure and the product was vacuumed at 1 mBar for 2 hours at 50 °C. The products
were obtained as white powders in quantitative yields.

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2.3.3.3
Termination
of
hyperbranched
polyaminopropylalkoxysiloxanes
with
trimethylchlorosilane and vinyldimethylchlorosilanes
The procedures for the termination of the corresponding hyperbranched
polyaminopropylalkoxysiloxane is shown in Schemes 7 and 8.
To the corresponding hyperbranched polyaminopropylalkoxysiloxane (0.017 mol) dissolved in
15 ml toluene, a solution of trimethylsilanol (0.0253 mol) or vinyldimethylsilanol (0.0253 mol) in
toluene (15 ml), or a mixture of trimethylsilanol (0.0101 mol) and vinyldimethylsilanol (0.0152)
was added in 30 min. The solution was left overnight with stirring. Next day, the solvent was
evaporated under reduced pressure and the product was vacuumed at 1 mBar during 1 hour at
50 °C. The products were obtained as colorless viscous liquids in quantitative yields.
2.3.3.4 Synthesis and stabilization of Ag nanoparticles with hyperbranched polyaminopropyl-
siloxane matrices
To a solution of the corresponding hyperbranched polyaminopropylsioxane (3.3 mmol) or
aminopropyltrialkoxysilane (3.3 mmol) in 40 ml CH3OH or CH3CN, AgBF4 (1.1 mmol) was added.
Three flasks with the reaction mixture were stirred both in the light and in the dark for 3 days
and irradiated for 30 min with a 125 watt mercury UV lamp. After that, the solvent was
evaporated and the product was vacuumed at 1 mBar. The products were obtained as brown or
dark orange gels in quantitative yields.
3.
Results and Discussion
3.1 Monosodium salts of aminopropylalkoxysilanes
Monosodium salts of aminopropylalkoxysilanes were synthesized by providing a reaction
between the corresponding aminopropyltrialkoxysilanes and sodium hydroxide (Scheme 1).
Scheme 1. Synthetic scheme for monosodiumoxyaminopropyldialkoxysilanes
The quantitative yields and purity of the monosodiumoxoaminopropyldialkoxysilanes thus
obtained were determined directly by means of 1H-, 13C-, 15N-, 29Si NMR and mass spectroscopy
methods, as well as indirectly, by analyzing the products of monosodium salts thus obtained,
1
13
15
29
capped with trimethylchlorosilanes (Scheme 2), by means of GPC, H, C, N, Si NMR and
mass spectroscopy.

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Scheme 2. Termination reactions of monosodiumoxoaminopropylalkoxysilanes
Reactions between alkoxysilanes and sodium hydroxide represent nucleophilic substitution of
the alkoxy group at the silicon atom with a hydroxide ion. Since replacement of one alkoxy
group in the molecule of the starting organoalkoxysilane by an electron-donor NaO- group
significantly reduces the reactivity of the silicon atom towards secondary nucleophilic
substitution reactions [23] (Fig. 3), the corresponding monosodiumoxoorganoalkoxysilane is
formed as the main product under certain conditions.
δ
Figure 3. Inductive electron effect in sodiumoxolalkoxysilane molecules.
In contrast to the reactions of NaOH with a number of organotrialkoxysilanes (where the
organic radical R = -CH3 or -CH=CH2) that occur at room temperature with a significant
exothermic effect and require optimization and thermal control for the reaction process and for
prevention of possible side reactions [6], reactions of aminopropyltrialkoxysilanes with NaOH
under standard conditions occur very slowly and elevated temperatures are needed. Such a
decrease in the reactivity of organoalkoxysilanes in nucleophilic substitution reactions on
transition towards aminopropyl organic substituents at the silicon atom can result from the
participation of the amino group in the complex rearrangement during the formation of a
transition complex, and can also be associated with the steric effect of the aminopropyl group.
At the same time, the coordination ability of amino groups can also lead to the prevention of
side reactions that often occur with a number of various organoalkoxysilanes [6].
3.2 Hyperbranched polyaminopropylalkoxysiloxanes
Monosodium salts of organoalkoxysilanes that have two types of chemically independent
functional groups are promising reagents for the creation of polyorganosiloxane structures with
controlled molecular architecture of the polymeric backbone (well-defined polysiloxane
structures).
Previously, based on a number of monosodium salts of alkoxysilanes (C2H5O)3SiONa [4] and
organoalkoxysilanes RSi(OC2H5)2ONa (R = CH3-, CH2 = CH-) [6], the possibility to synthesize the
corresponding polysiloxanes and polyorganosiloxanes with hyperbranched structures was
demonstrated. Similarly, in this work, based on the synthesized monosodium salts of
aminopropyltrialkoxysilanes,
the
possibility
to
prepare
hyperbranched
polyaminopropylsiloxanes by controlled polycondensation was studied and demonstrated.

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Monosodiumoxoorganodialkoxysilanes are AB2-type monomers (Fig. 4).
Figure 4. Monosodium salts of organotrialkoxysilanes - AB2-type monomers
In accordance with the Flory condition [15], due to which totally acyclic polymers with
hyperbranched structures can be synthesized without the risk of gelation in heterofunctional
polycondensation of a monomer containing more than two functional groups of different
chemical nature, polycondensation of the corresponding sodiumoxoaminopropyldialkoxysilanes
was provided (Scheme 4).
Scheme 4. Synthetic scheme for hyperbranched polyaminopropylalkoxysilanes
The polycondensation was carried out in accordance with the method known as "silanol"
method [2,3], in which a sodiumoxoorganodialkoxysilane solution undergoes neutralization
with an equimolar amount of acetic acid, thus forming hydroxyorganodiethoxysilane, which
undergoes an in-situ heterofunctional condensation to give the corresponding hyperbranched
polyorganoalkoxysiloxane.
This method is based on the previously discovered effect of activation of alkoxy groups in
sodiumoxoalkoxysilane molecules due to the positive inductive effect of NaO- groups towards
the reagents with mobile protons (such as, for example, silanols) (Scheme 5) [6].
δ
δ
δ
Scheme 5. Mechanism of heterofunctional condensation of sodiumoxyalkoxysilane and silanol.

ACCEPTED MANUSCRI2P9T
1
13
15
A number of NMR spectroscopy methods such as H, Si, C, and N NMR spectroscopies
were used for characterization and estimation of the molecular structures of the polymers thus
obtained.
1
It follows from the ratio of the integral intensities of H NMR proton signals (Fig.5) of
polyaminopropylalkoxysiloxanes that the condensation of sodiumoxyorganodiethoxysilanes in
the presence of acetic acid is a heterofunctional process that occurs solely as a reaction
between the alkoxy and hydroxy groups generated in the neutralization of the corresponding
sodium salts, and thus this process obeys the Flory rule.
:
1
1
Figure 5. 1H NMR spectra (CDCl3) of polyethylenediaminopropylmethoxysilane
A 29Si NMR study (Fig. 6) of the resulting hyperbranched polyvinylethoxysiloxanes with addition
of paramagnetic chromium(III) acetylacetonate serving as a relaxation accelerator [24] allowed
us to obtain data on the ratio of different siloxane units in the structures of the polymers
synthesized.
As a rule, molecules of hyperbranched polymers obtained from the AB2 type monomers consist
of linear (L) units with one unreacted functional group; dendritic (D) units without functional
groups, and terminal (T) units with two unreacted functional groups.
To provide a quantitative relationship between different units in the structure of
hyperbranched polymers and thus obtain a description of their molecular structures, it is
worthwhile to use the appropriate equation for calculating the degree of branching, DB: DB =
(D + T) / (D + L + T) [24].
While the degree of branching of an ideal dendrimer equals 1, it usually does not exceed 0.5 for
hyperbranched polymers with less-perfect structures obtained from AB2-type monomers and
possessing a considerably broader polydispersity index [25]. The degree of branching found
from the previous equation was 0.43 for the polyaminopropylethoxysiloxane synthesized and
0.49 for the polyethylenediaminopropylmethoxysiloxane.
OAlk
OAl
O
R
Si
O
T
R
Si
O
T
R
Si OAlk
O
L
OAlk
OAl
O
R
Si OAlk
O
L
O
Si
O
O
Si
O
R
O
R
O
D
D

ACCEPTED MANUSCRIPT
Figure 6a. 29Si NMR spectra of
polyaminopropylethoxysilane
Figure 6b. 29Si NMR spectra of
polyaminopropylethoxysilane
The molecular weights and molecular weight distribution of the amino-containing
polyalkoxysiloxanes obtained were determined indirectly by GPC analysis of the products
obtained upon termination of the polymers with phenyl isocyanate (Scheme 6).
Scheme 6. Synthetic scheme of termination of amino groups in hyperbranched
polyaminopropylalkoxysiloxane (HBPAPES) with phenyl isocyanate.
The need to convert amino groups by means of additional capping reactions is due to the
complexity of studies of amino-containing polymers with standard GPC techniques due to the
specific interactions of amino groups with GPC column fillers, which lead to the adsorption of
such polymers on the column, and thus making them impossible to detect and determine their
molecular weight characteristics [26].
The GPC curves obtained for capped polymers correspond to the average mass molecular
weights in the range from 900 to 1200 kDa in polystyrene standards, corresponding to
Mw = 500 - 900 kDa for the initial samples.
Thus, polycondensation of the monosodium salts of aminopropylalkoxysilanes by the above
method leads to the production of hyperbranched polymers with relatively small molecular
weights corresponding to polyorganosiloxane structures with ≤10 repeating
organoalkoxysiloxane units.
The large number of residual alkoxy groups in polymer structures allows its further chemical
modification. At the same time, the presence of a large number of basic amino groups in the
polyaminopropylalkoxysiloxanes obtained makes these systems highly reactive and easily
condensable through the residual alkoxy groups, thus permitting the modification of such
polymers without the use of any additional catalysts.
To obtain more chemically stable terminated derivatives of polyaminopropylsiloxanes, their
residual alkoxy groups were converted in to trimethylsiloxy groups. This chemical conversion
was carried out by hydrolytic condensation between polyaminopropylalkoxysiloxanes and
trimethylsilanol autocatalyzed by the own amino groups of the polymers (Scheme 7).

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R
R
HN
R
HN
R
NH
NH
O
OAlk
O
O
TMSO
OTMS
Si
Si
Si
O
OAlk
Si
OAlk
O
O
Si
OTMS
O
O
Si
CH3
HO Si CH3
CH3
O
Si
Si
O
Si
Si
O
R
O
OAlk
R
OTMS
NH
O
NH
O
OAlk
OTMS
Si
O
Si
O
-AlkOH
HN
HN
HN
HN
TMSO
OAlk
O
R
R
Si
R
Si
R
HN
HN
O
O
R
R
O
O
O
R
R
H N
Si
Si
HN
Si
Si
OAlk
O
O
HN
OTMS
HN
R
R
HN
HN
R
R
Scheme 7. Synthetic scheme of termination of hyperbranched polyaminopropylalkoxysilanes
with trimethylsilanol.
Due to the heterofunctional mechanism of the condensation reactions of silanol and alkoxy
groups catalyzed by amines and accompanied by the formation of the corresponding alcohols
as by-products [26] and the absence of homofunctional condensation processes which could
lead to H2O formation in the system, the termination of polyaminopropylsiloxanes does not
involve side reactions of intra- as well as intermolecular "cross-linking" of polymers. It occurs
quantitatively and with preservation of their initial hyperbranched polymer architectures. The
completeness of the termination reactions was estimated by 1 H NMR spectroscopy (Fig. 7).
Figure 7. 1H NMR spectra (CDCl3) of polyaminopropylethoxysiloxane (a) and
polyethylenediaminopropylmethoxysiloxane (b) before (▬) and after (▬) the termination with
trimethylsilanol.
By varying the type of the blocking agent, the method developed allows one to perform
polymer-analogous transformations of the resulting polymers through their residual alkoxy
groups, thus making it possible to obtain structures with different organic radicals and
functional groups in the polymer structures. In fact, when dimethylvinylsilanol was used as the
blocking agent, latent reactive vinyl groups were introduced into the structure of

ACCEPTED MANUSCRIPT
hyperbranched polyethylenediaminopropylmethoxysilane in an amount equimolar to the initial
amount of alkoxy groups (Scheme 8, Fig.8).
Si
Si
O
O
H
CO
O
O
OCH
3
3
N
H
N
NH
2
NH
2
Si
O
Si
O
H
Si
Si
Si
O
O
H N
2
O
Si
H N
OCH
N
H
N
3
2
H
OH
Si
O
Si
Si
O
HO
O
H
N
H
-CH OH
3
H N
2
H N
2
N
i
Si
O
S
Si
H CO
Si
HN
NH
2
HN
NH
2
O
O
O
O
3
Si
HN
NH
HN
NH
2
2
Scheme 8. Synthetic scheme of the capping reaction of hyperbranched
polyethylenediaminopropylmethoxysiloxane (HBPEDAPMS) with dimethylvinylsilanol.
Figure 8. 1H NMR spectra (CDCl3) of polyethylenediaminopropylmethoxysiloxane before (▬)
and after (▬) capping with vinyl dimethylsilanol (from bottom).
Simultaneous usage of different blocking agents makes it possible to obtain polysiloxane
structures with an exactly specified ratio of different terminal units.
Thus, using trimethyl- and dimethylvinylsilanol as the blocking agents, polymeric structures
with previously calculated concentrations of terminal vinyl groups were obtained (Scheme 9).

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Scheme 9. Synthetic scheme of the capping reaction of hyperbranched
polyaminopropylethoxysiloxane (HBPAPES) with trimethyl- and dimethylvinylsilanol; synthesis
of hyperbranched polyorganosiloxane with two types of terminal groups.
3.3 Synthesis and stabilization of Ag nanoparticles with hyperbranched
polyaminopropylsiloxane matrices.
The synthesized hyperbranched polyethylenediaminopropylsiloxane matrix (HBPEDAPS),
terminated with trimethylsilyl groups, was used to obtain and stabilize Ag nanoparticles in
methanol solution (Scheme 10). The absorption spectrum of the initial HBPEDAPS matrix in
methanol, which was used both as the reaction medium and the reducing agent [27], contains
very weak absorption bands in the 260-400 nm region and an intense absorption band with a
maximum presumably lying in the vacuum ultraviolet region (Fig. 9, curve 1). After irradiating
the mixture of the matrix and AgBF4 for 30 minutes with a mercury lamp [Sylvania HSW 125W
E27 Blacklight], a clear intense band of plasmon resonance with a maximum at 413 nm, typical
of Ag nanoparticles [28], appears in the absorption spectrum of the mixture (Fig. 9, curve 2).
The average size of the resulting nanoparticles found by DLS method was 7-16 nm (Fig. 10).
However, TEM showed that the roughly spherical polydisperse Ag nanoparticles corresponded
to smaller sizes of approximately 1-10 nm (Fig.11). This difference should be a consequence of
the fact that the dimensions found by the DLS method correspond to the sum of the sizes of the
nanoparticles forming the core and the polymeric matrix forming the shell, whereas TEM
exclusively shows the dimensions of silver nanoparticles.
The resulting Ag nanoparticles successfully stabilized by the HBPEDAPS matrix undergo no
aggregation or precipitation of the particles from the solution for at least 24 hours. Re-
examination of the polymer composite after more than a month of storage in a dry state also
showed the stability of silver nanoparticles and preservation of their initial size.
Scheme 10. Synthetic scheme of the stabilization of Ag nanoparticles with HBPEDAPS matrix in
methanol.

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Figure 9. Absorption spectra of the HBPEDAPS matrix in methanol (5 mg/ml)
(1) and a mixture of the HBPEDAPS matrix and AgBF4 in methanol after
irradiation (2).
Figure 10. Distribution of Ag nanoparticles obtained after irradiation of a
solution of the HBPEDAPS matrix and AgBF4 in methanol, estimated by DLS
method.

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Figure 11. TEM image of Ag nanoparticles stabilized with HBPEDAPS matrix (A); electron
diffraction ring pattern from a crystalline Ag specimen (B).
Unlike with the HBPEDAPS matrix, no formation of Ag nanoparticles was observed under similar
conditions in the case of the hyperbranched polyaminopropylsiloxane (HBPAPS) matrix.
Under the same conditions, the use of solutions of the corresponding
aminopropyltrialkoxysilane monomers instead of the hyperbranched polymers synthesized in
this study leads to the formation of a black precipitate. As observed, silver is recovered from
the salt, but the monomers are unable to stabilize the Ag nanoparticles produced, thus leading
to their precipitation and oxidation.
4.
Conclusions.
It has been shown that the reaction of NaOH with commercially available
aminopropyltrialkoxysilanes is a simple and effective way to synthesize amino-containing
organosilicon monomers with two types of chemically independent functional -ONa and -OAlk
groups that are promising reagents for the creation of siloxane structures with controlled
molecular architecture and functionality.
As an example, one of the possible uses of such AB2-type monomers was demonstrated by the
synthesis
of
hyperbranched
structures
in
controlled
polycondensation
of
monosodiumoxoaminopropyldialkoxysilanes.
The presence of a large number of residual alkoxy groups in the structure of the polymers
synthesized allows further modifications of the surface of branched polymers, thus allowing
their polymer-analogous transformations leading to the formation of polymer shells of various
chemical nature.
The polymer matrices with ethylenediaminopropyl organic radical (HBPEDAPS) that we
synthesized showed the ability to stabilize silver nanoparticles, whereas monomeric
aminopropylalkoxysilanes did not possess such a stabilizing ability under the same conditions.
An important feature of the systems obtained is their water solubility, which, in combination
with the high coordination ability of amino groups and the demonstrated ability of these
polymer systems to stabilize metallic nanoparticles, makes the usage of these compounds
potentially promising in areas related to biological or medical applications.
Acknowledgments
We are grateful to the RSF (Grant Nos. 16-13-10521 and MK – 5726.2016.3) for financial support of this
study.
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Highlight
Based on the commercially available aminopropyltrialkoxysilanes new monosodium
salts of organoalkoxysilanes (sodiumoxoaminopropyldialkoxysilanes) with two types of
chemically independent functional -ONa and -OAlk groups at the silicon atom were synthesized
and characterized. The obtained sodiumoxoaminopropyldialkoxysilanes can be regarded as
AB2-type monomers - promising reagents for providing controlled polycondensation and
production of functional organosilicon polymers with controlled molecular architectures.
Consequently polyaminopropylsiloxanes with hyperbranched molecular architectures were
obtained by heterofunctional polycondensation of the corresponding AB2-type
monosodiumoxoorganodialkoxysilanes. Synthesized structures were characterized with
29
1
methods of Si-NMR, H-NMR, GPC and elemental analyzes. Thus obtained hyperbranched
polymer matrices, containing aminopropyl- organic radicals, showed the ability to stabilize
silver nanoparticles.