Mendeleev Commun., 2018, 28, 272–274
Table 2 Physicochemical properties of DF1-modified copolymers.
DF1 content
Me
C
Me
C
HO
4
(DF1)
Functionalization Yield of modified Tg /°C T10%/°C
CH2
CH2
(
mol%)
x
y
n
i
1
degree (%)
copolymer (%)
(DSC) (TGA)
C
C
( H NMR)
O
OMe
O
OH
1
2
3
8
1
0
90
73
77
92
88
53
96
72
95
291
276
263
Me
C
Me
Me
CH2
CH2
OMe
C
C
CH2
C
C
x
y
z
n
C
O
O
OH
O
O
Table 3 Characteristics of DF1-modified copolymer film.
z = 0.18, 0.21, 0.30
DF1 content (mol%) Film thickness/nm Tp/°C
F
d33/pm V–1
1
2
3
8
1
0
290
310
297
110
110
110
0.38
0.25
0.19
22
23
28
Scheme 2 Reagents and conditions: i, DCC, DMAP, THF, 25°C.
on their composition. The glass transition temperature (T ) of
g
copolymers grows with the increase in MAA content, which is
apparently due to the formation of a physical network in the
copolymers. The same trend is observed when comparing the
thermal stability of copolymers.
According to the presented data, the degree of functionalization
and yield of chromophore-containing copolymers decrease with
raising the MAA content in the copolymer composition, which is
apparently associated with steric hindrances.
The introduction of chromophores into the copolymers was
carried out by the Steglich esterification reaction under mild con-
ditions (Scheme 2). The modified copolymers appeared as red
powders easily soluble in polar solvents. Their structure was
confirmed by physicochemical methods. In their IR spectra,
absorption bands corresponding to the groups characteristic of
MMA–MAA copolymers were retained, and new absorption bands
With increase of the chromophore concentration, the thermal
stability of the copolymers decreases, which can be explained by
the lower thermal stability of the chromophore itself (T = 250 °C).
d
The copolymers obtained have good film-forming properties;
the thickness of the cast films measured by the AFM method is
290–310 nm.
The resulting films were transferred to the electret state in
the corona discharge field using the standard procedure.15 Order
parameter (F) characterizing the efficiency of chromophore
orientation, is determined from the UV-VIS spectra by the change
in absorption intensity of the film before and after poling.15 NLO
coefficients (d ) of the obtained materials, determined by the
corresponding to the multi-chromophore fragments appeared: 1600
,
–
1
–1
–1
1
(
588, 1446 cm (arene); 1253, 1139 cm (C–O–C); 1386 cm
N=N); 1513, 1336 cm–1 (NO ). Their H NMR spectra contained
1
2
signals for the ortho- and meta-protons of azobenzene moieties
as doublets at 6.93, 7.90, 7.95 and 8.33 ppm; signals for the
ortho- and para-protons of the aromatic branching center at
3
3
3
+
SHG technique (Nd :YAG laser, l = 1064 nm, pulse duration
–
2
6
.57 and 6.38 ppm, respectively, and a broad signal at 4.5 ppm
15 ns, power density on the sample 10 kW cm ) are given in
Table 3.
for the benzylic methylene protons tethering the dendritic
fragments to the oligomer chain. Moreover, in the region of 3.9 and
As can be seen from Table 3, the values of NLO coefficients
increase with raising the concentration of chromophores. The data
we obtained earlier for materials based on epoxy-amine oligomers
with multichromophore dendritic fragments showed that sufficiently
high values of NLO coefficients could be achieved by performing
4.2 ppm, the signals of the ethylene tether groups are manifested,
the methyl protons resonate at 1.26 ppm. Signals for the hydroxyl
group (ca. 11 ppm) are absent. Proton signals of the polymer chain
at 3.67 ppm (MeO), 1.86–1.93 ppm (CH ) and 1.17–1.05 ppm
2
16
(Me) are regularly present.
the poling at the temperature T exceeding T by ~30°C. Taking
p g
TheUV-VISspectraoffunctionalizedcopolymerswererecorded
this into account, we can expect the d33 values of the obtained
materials to increase upon optimizing the poling regime.
Repeated d33 measurements performed after four months
showed a decrease in the NLO response by ~60%. To enhance
the relaxation stability of the response, we propose to perform
cross-linking of the copolymer chains by addition of glycidyl
methacrylate to the obtained copolymers.
In summary, we have obtained novel polymer materials based on
methacrylic copolymers with dendritic chromophore-containing
fragments (DF1) in the side chain, which demonstrate rather
high nonlinear optical coefficients. The best value of 28 pm V–1
was found for dendritic fragment content of 30 mol%.
in THF solution at the polymer concentration of 2×10– mol dm
(
5
–3
Figure 1). The presence of a broad peak at 300 nm corresponds
to electronic π–π* transitions for aromatic rings; and a more
intense symmetric absorption band in the long-wavelength region
with lmax = 472–476 nm is due to superimposed n–π* and π–π*
transitions of azobenzene chromophore groups. Some charac-
teristics of the resulting chromophore-containing copolymers are
given in Table 2. The concentration of DF1 units and the degree
1
of functionalization were determined from H NMR spectra.
1
0
0
0
0
0
.0
.8
.6
.4
.2
.0
3
This work was supported by the Program of Presidium of the
Russian Academy of Sciences no. 38 ‘The study of the fundamental
problems of synthesis and structure–activity relationship for the
development of new chemical substances and materials’. AFM
investigations were carried out in the Spectroscopy, Microscopy
and ThermalAnalysis laboratory of Kazan National Research Tech-
nological University. We are grateful to Professor E. S. Nefed’ev
for cooperation.
2
1
3
00
400
500
l/nm
600
700
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi: 10.1016/j.mencom.2018.05.014.
Figure 1 UV-VIS spectra of methacrylic copolymers with different DF1
content: (1) 18, (2) 21, and (3) 30 mol%.
–
273 –
Vakhonina, Tatyana A.
