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SOLOVSKII et al.
spectra of copolymers 1, evidencing the presence of
p-crotonoyloxybenzaldehyde units in terpolymers 2.
evaporator temperature 300°С, column temperature
(final) 220°С, gas flow rate 20 mL/h, sample volume
1 µL. DMF was purified as described elsewhere [11].
DCC (Fluka) and 2-propanol (Vekton) were used as
received.
The synthesized terpolymers 2 contained 7.7–
10.8 mol % of carboxylic groups and 10.2–21.0 mol %
of aldehyde groups. This is enough for binding of
several bioactive substances. Sample 2а containing
<10 mol % of carboxylic groups can be used as the
targeted delivery system after introduction of the
vector groups.
Crotonic acid (Merk) was twice recrystallized from
water in the presence of activated carbon, mp 71°С.
Found, %: С 55.64; Н 6.72. C4H6O2. Calculated, %: С
55.81; Н 6.98.
AIBN initiator was purified as follows. 46 g of
AIBN was heated on a water bath in a mixture of
100 mL of chloroform and 80 mL of ethanol, the
temperature not exceeding 40°С. The major fraction of
AIBN was dissolved. The insoluble coagulated
particles were filtered off on a Buchner funnel. 400 mL
of ethanol was added to the transparent filtrate. The
obtained solution was kept at –10°С for 20 h. The
precipitate was collected on a Buchner funnel and
dried under vacuum of a water-jet pump. The obtained
product was dissolved in a mixture of 40 mL of
chloroform and 30 mL of ethanol. The solution was
kept at –10°С for 20 h. The obtained product was
collected on a Schott filter and dried under vacuum to
constant mass. Yield of the purified AIBN 25.3 g
(55%), mp 103°С. Found, %: С 57.97; Н 7.27.
C8H12N4. Calculated, %: С 58.53; Н 7.31.
EXPERIMENTAL
The composition of copolymers 1 and 2 were
determined by potentiometric titration of carboxylic
groups with 0.1 М. solution of NaOH using a HJ 2210
pH-meter. The determination of hydrodynamic (MSD)
and weight-average (Mw) molecular masses was
performed as described in [8] and [7], respectively.
Hydrodynamic radius of the scattering objects was
determined using the regularization method [9]. The A2
parameter was calculated using the Debye equation [9]
from the data on static light scattering of the copoly-
mers solutions. Partial specific volume was determined
by pycnometry. Polydispersity index of the copoly-
mers of N-vinylpyrrolidone with crotonic acid was
determined from the GPC data. The GPC experiments
were performed using a system of microstyrogel
chromatography columns (Waters/Millipore) with
porosity of 102, 103, and 105 nm; with DMF as the
solvent. The chromatograph was calibrated using
narrow fractions of polystyrene references. The
calibration for poly-N-vinylpyrrolidone was calculated
from the universal Benoit’s calibration.
p-Oxybenzaldehyde. A mixture of 170 mL of
freshly distilled anisaldehyde and 400 g of pyridinium
chloride was stirred at 170°С for 3 h. A hot solution
was poured into 1.5 L of cold water. The obtained oil
was extracted with diethyl ether. The extracts
(~600 mL) were dried over anhydrous sodium sulfate
for 24 h. Ether was distilled off; the residue was dried
under vacuum and twice recrystallized from water with
addition of activated carbon. Yield 76.5 g (45.2%), mp
113°С. Found, %: С 68.37; Н 4.6. C7H6O2. Calculated,
%: С 68.85; Н 4.95.
Electronic absorption spectra were recorded using
an SF-256 spectrophotometer. NMR spectra (DMSO-
d6) were registered using a Bruker Avance II-400
spectrometer [400.1 (1H) and 100.6 MHz (13С)]. IR
spectra were registered using a Bruker JFC 88 FTIR
spectrometer in KBr pellets. Viscometry measurements
were performed using an Ubbelohde viscometer in
0.1 M aqueous solution of sodium acetate at 25°С; the
solvent flow time was 142.3 s.
Synthesis of co-polymers 1a–1i. AIBN and a
solution of a mixture of N-vinylpyrrolidone and
crotonic acid in propanol-2 were put in an ampoule.
The mixture was bubbled with argon; the ampoule was
sealed at heated at 65°С for 48 h. The copolymer was
isolated from the polymerizate by precipitation in
diethyl ether, collected on a Schott filter, dried under
vacuum, and reprecipitated from 2-propanol into
diethyl ether.
N-Vinylpyrrolidone (Lancaster) was purified by
double vacuum distillation over KOH; a fraction with
bp 60–62°С (2–3 mmHg) was collected, nD20 1.5110
(nD20 1.517 [10]). According to GLC data, the purity of
the obtained N-vinylpyrrolidone was 99.7%. GLC
conditions: Hewlett-Packard chromatograph, PEG
modified with nitroterephthalic acid as the sorbent,
helium as the carrier gas, flame ionization detector,
Synthesis of terpolymers 2. A solution of DCC in
5 mL of DMF was added to a solution of co-polymer 1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 88 No. 3 2018