Polarization, excited states, trans-cis properties and anisotropy of thermal and electrical conductivity of the 4-(phenyldiazenyl)aniline in PVA matrix

Article abstract of DOI:10.1016/j.molstruc.2017.04.014

In the present work, Polarization, Excited States, Trans–Cis (E?→?Z) Isomerization Properties and Anisotropy of Thermal and Electrical Conductivity of the 4-(phenyldiazenyl)aniline in the presence of polyvinyl alcohol (PVA) matrix were studied. DFT, UV/Vi

Full text of DOI:10.1016/j.molstruc.2017.04.014

Accepted Manuscript
Polarization, excited states, trans-cis properties and anisotropy of thermal and
electrical conductivity of the 4-(phenyldiazenyl)aniline in PVA matrix
Siyamak Shahab, Liudmila Filippovich, Masoome Sheikhi, Rakesh Kumar, Evgenij
Dikusar, Hooriye Yahyaei, Alexander Muravsky
PII:
S0022-2860(17)30445-3
10.1016/j.molstruc.2017.04.014
MOLSTR 23636
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 12 January 2017
Revised Date: 4 April 2017
Accepted Date: 5 April 2017
Please cite this article as: S. Shahab, L. Filippovich, M. Sheikhi, R. Kumar, E. Dikusar, H. Yahyaei, A.
Muravsky, Polarization, excited states, trans-cis properties and anisotropy of thermal and electrical
conductivity of the 4-(phenyldiazenyl)aniline in PVA matrix, Journal of Molecular Structure (2017), doi:
10.1016/j.molstruc.2017.04.014.
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Graphical Abstract
Polarization, Excited States, Trans–Cis (E→Z) Isomerization Properties and Anisotropy of
Thermal and Electrical Conductivity of the 4-(phenyldiazenyl)aniline in the presence of
polyvinyl alcohol (PVA) matrix were studied. DFT, UV/Vis, IR-Spectroscopies and Indicator
Method were used for Determination of Thermal Conductivity of polymer films. The molecular
HOMO-LUMO, excitation energies and oscillator strengths for E and Z isomers of the 4-
(phenyldiazenyl)aniline have also been calculated and presented. Optical Properties of the PVA-
films containing 4-(phenyldiazenyl)aniline have been also investigated.

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Title Page Information
Sub: Submission of Revised manuscript for full paper in Journal of Molecular Structure
Dear Sir,
Please find herewith the enclosed manuscript:
Article title
Polarization, Excited States, Trans-Cis Properties and Anisotropy of Thermal and Electrical Conductivity of
the 4-(phenyldiazenyl)aniline in PVA Matrix
The name of journal
Journal of Molecular Structure
The author’s affiliations with full postal address
Siyamak Shahab
Institute of Physical Organic Chemistry
National Academy of Sciences of Belarus, 13 Surganov Str., Minsk 220072
E-mail: siyamak.shahab@yahoo.com
Liudmila Filippovich
Institute of Physical Organic Chemistry
National Academy of Sciences of Belarus, 13 Surganov Str., Minsk 220072
E-mail: luda1977@list.ru
Masoome Sheikhi
Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan, Iran
E-mail: Masoome Sheikhi2@gmail.com
Rakesh Kumar
Department of Chemistry,DAV University , Jalandhar -144012 (Punjab) India
E-mail: rakesh_nitj@yahoo.co.in
Dikusar Evgenij Anatol’evich
Institute of Physical Organic Chemistry
National Academy of Sciences of Belarus, 13 Surganov Str., Minsk 220072
E-mail: dikusar@ifoch.bas-net.by
Hooriye Yahyaei
Department of Chemistry, Zanjan Branch, Islamic Azad University, Zanjan, Iran
Email id : hoorie_yahyaei@yahoo.com
Alexander Muravsky
Institute of Chemistry of New Materials, National Academy of Sciences of Belarus, 36 Skarina Str., Minsk 22014
E-mail: alexander.muravsky@ichnm.basnet.by

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Polarization, Excited States, Trans-Cis Properties and Anisotropy of Thermal and
Electrical Conductivity of the 4-(phenyldiazenyl)aniline in PVA Matrix
Siyamak Shahaba,b, Liudmila Filippovicha,b
Yahyaeie, Alexander Muravskyb
,
Masoome Sheikhic, Rakesh Kumard, Evgenij Dikusara, Hooriye
aInstitute of Physical Organic Chemistry, National Academy of Sciences of Belarus,13 Surganov Str, Minsk 220072
bInstitute of Chemistry of New |Materials, National Academy of Sciences of Belarus, 36 Skarina Str., Minsk 220141
cDepartment of Chemistry, Gorgan Branch,Islamic Azad University, Gorgan, Iran
dDepartment of Chemistry, DAV University, Jalandhar - 144012 (Punjab) India
eDepartment of Chemistry, Zanjan Branch, Islamic Azad University, Zanjan, Iran
ABSTRACT
In the present work, Polarization, Excited States, Trans–Cis (E→Z) Isomerization Properties and
Anisotropy of Thermal and Electrical Conductivity of the 4-(phenyldiazenyl)aniline in the
presence of polyvinyl alcohol (PVA) matrix were studied. DFT, UV/Vis, IR-Spectroscopies and
Indicator Method were used for Determination of Thermal Conductivity of polymer films. The
absorption spectra of the 4-(phenyldiazenyl)aniline in dimethylformamide (DMF) solvent and in
aqueous medium were calculated. The nature of absorption peaks of the 4-
(phenyldiazenyl)aniline in the UV/Vis spectral regions were interpreted. The solvent effect on
the absorption spectrum of the 4-(phenyldiazenyl)aniline has established. The molecular HOMO-
LUMO, excitation energies and oscillator strengths for E and Z isomers of the 4-
(phenyldiazenyl)aniline have also been calculated and presented. Optical Properties of the PVA-
films containing 4-(phenyldiazenyl)aniline have been also investigated. Polarizing Efficiency
(PE) of obtained PVA-film is 98-99 % at Stretching Degree (Rs) 3.5. Anisotropy of thermal and
electrical conductivity of PVA-films containing E and Z isomers of the 4-(phenyldiazenyl)aniline
was also measured and discussed.
Keywords: Polarization, excited state, trans-cis isomerization, anisotropy of thermal conductivity, PVA matrix
Corresponding authors: m.sheikhi2@gmail.com (M. Sheikhi); rakesh_nitj@yahoo.co.in ( R. Kumar)
1. Introduction
Organic compounds induce electro-optic effects and produces large nonlinear optical responses
due to the large delocalization of π electrons compared to the more traditional inorganic
compounds [1]. For the production of organic nonlinear optical (NLO) compounds donor
and/or acceptor substituents such as azo-, amino-, nitro-, cyano-, halo-, hydroxyl are used. Azo

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compounds contain nitrogen as the azo (-N=N-) group that are one of the important synthetic
organic dyes [2]. They are used as colorants in the textile, paper, cosmetics, drugs, foods
coloring, and other consumer goods. They are promising systems for dyestuffs, pH indicators [3-
6] and optical applications such as holographic and digital storage, polarizing films, lasers [7-12]
liquid crystal command surfaces and nonlinear optical devices [13]. 4-(phenyldiazenyl)aniline is
an aromatic amine and an intermediate in the production of diazo dyes. The single crystals of 4-
(phenyldiazenyl)aniline were reported by Eazhilarasi and coworkers [14]. In recent years,
computational chemistry has become an important tool for chemists and a well-accepted partner
for experimental chemistry [15-17]. Density functional theory (DFT) method has become a
major tool in the methodological arsenal of computational organic chemists. The trans–cis
(E→Z) isomerization is observed for azobenzene and its derivatives, which has recently
considered in optical materials [4,18], media storage materials [19], light-triggered nano-
machines [6,20], etc. The trans–cis (E→Z) isomerization can readily occur at room temperature
and can be promoted by visible light irradiation. The DFT and CASSCF calculations were
performed to optimize the 4-(phenyldiazenyl)aniline and scan the potential energy surfaces
(PES) of the transition state structures S0(n→π*) and S1(π→π*) [21]. The initial development of
photoinduced anisotropy in highly photosensitive monolayers of an aminoazobenzene molecule
(a derivative of o-methyl red) that are initially randomized using circularly polarized light is
found to be significantly slower than in monolayers randomized by thermal relaxation.
Youngwoo Yi and coworkers [22] propose that this is a direct consequence of the slow thermal
relaxation of isomers from the cis to the trans state and suggest that such considerations are
important in designing even more sensitive photoactive monolayers and in understanding their
photodynamics. The absorption spectra of three azoaminobenzene dyes and two its derivatives
have been computed with TD-DFT approach using four hybrid functional, different basis sets
and four salvation model such as PCM, I-PCM, SCI-PCM and IEF-PCM [23,24]. The aim of the
current work is to study polarization, excited states, trans–cis (E→Z) isomerization properties
and anisotropy of thermal conductivity in colored by 4-(phenyldiazenyl)aniline PVA-films by
DFT, UV/Vis, IR-Spectroscopies and Indicator Method for Determination of Thermal
Conductivity of polymer films.

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2. Experimental
2.1 Reagent and Apparatus
All chemical used in this study were of analytical reagent grade. Used PVA «Mowiol 28-99»
manufactured by the Hoёchst Aktiengesllschaft Co., Germany The (E)-4-
.
(phenyldiazenyl)aniline was purchased from Sigma-Aldrich Co. and used without further
purification. Experimental UV/Vis spectrum of the compound was recorded on UV-Visible
Spectrophotometer Cary 300 (Varian, USA). Experimental IR-spectrum of films was recorded in
the frequency region 400-4000 cm-1 on a Spectrophotometer of Protégé 460 (Nicolet, US).
Trans–cis (E→Z) isomerization of films was studied using unfiltered radiation of high-pressure
Hg-lamp DRSH-1000 (Belarus). The intensity of light falling perpendicular to the surface of the
sample was 0.009 W/cm2. At exposure temperature of sample was 20-22 °C. The absorption
spectra of the films were measured before and after UV radiation. Thermal and electrical
conductivity of PVA-films was measured on the complex equipment LC – 201 (Alfa Laval
Group, Sweden).
2.2 Preparation of PVA-films containing the (E)-4-(phenyldiazenyl)aniline
The PVA-films were prepared from (wt. %) 10 PVA solution containing 0.01-0.03 of the (E)-4-
(phenyldiazenyl)aniline (0.10-0.30 in colored dried PVA-film), 0.01 boric acid (H3BO3), 6.0
ethyl alcohol (C2H5OH), 0.5 dimethylformamide (DMF) and water. An initial composition was
prepared by dissolving PVA in distilled water and ethyl alcohol. The composition was mixed at
temperature 80-85 °C. (E)-4-(phenyldiazenyl)aniline and additives were added after 3 h. after
starting of heating PVA solution at intervals 20 minutes. (E)-4-(phenyldiazenyl)aniline was
dissolved in dimethylformamide previously. The mixture was heated for 3.5 h. The hot solution
was filtered through two layers of technical nylon. Deaeration was occurred during 10 h. The
composition was cast on the polished glasses and dried in the closed box at temperature 20-22
°C. Uniaxial orientation was done in the 4 % boric acid solution at temperature 42-45 °C. The
washed film was dried for 35 minutes at temperature 60-63 °C. The value of Stretching Degree
(Rs) was determined as the ratio between length of the films after and before (laft / lbef) uniaxial
orientation. The thickness of the resulting films was between 60 to 65 µm. The film thickness
was measured with a micrometer with an accuracy of ± 5µm (GS SSSR 6507-90).

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3. Optical properties
3.1 Polarization Properties of PVA-films containing the (E)-4-(phenyldiazenyl)aniline
The main optical properties of polarizing films such as Transmittance (Tmax, Tmin), Polarizing
Efficiency (PE) and Dichroic Ratio (Rd) were evaluated at the absorption maximum of the
polarizing films according to Eqs. (1,2) [12,24]:
PE = (Tmax – Tmin) / (Tmax + Tmin) * 100
Rd = Dmax / Dmin
(1)
(2)
Where, Tmax, Tmin, Dmax and Dmin - Absorbance and Transmittance for linearly polarized light
parallel and perpendicular to direction of stretching of colored PVA-film. Polarizing Efficiency
(PE) of colored oriented PVA-films depends on the concentration of injected (E)-4-
(phenyldiazenyl)aniline and Stretching Degree (Rs = 3.5) of the films, therefore the optimum
concentration of the (E)-4-(phenyldiazenyl)aniline in PVA-film was obtained (Fig. 1).
Fig. 1 Transmission spectra (1 – Т||, 2 – Т ) and polarizing efficiency (3 – PE) of polarizing PVA-films containing
0.30 wt. % of the (E)-4-(phenyldiazenyl)aniline.
Changes in concentration of the (E)-4-(phenyldiazenyl)aniline from 0.10 to 0.30 wt. % in the
colored oriented PVA-film show that with increasing concentration of the (E)-4-
(phenyldiazenyl)aniline, maximum light transmission in parallel and perpendicular direction are
reduced. At [(E)-4-(phenyldiazenyl)aniline] = 0.30 wt. % Tmax = 45.3 %, Tmin = 0.25 % (photo of
the polarizing PVA-film containing 0.30 wt. % of the (E)-4-(phenyldiazenyl)aniline in parallel
and perpendicular directions of stretching is presented in Fig. 2 a,b). PVA-film effectively

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polarizes the light from UV (353 nm) to Visible region (466 nm) of spectrum with PE = 98-99
%.
Field of
Dichroism
(a)
(b)
Fig. 2 PVA-films containing the 0.30 wt. % of the (E)-4-(phenyldiazenyl)aniline in parallel (a) and perpendicular (b)
directions of stretching
The best optical parameters has PVA-film containing 0.30 wt. % of the (E)-4-
(phenyldiazenyl)aniline (Tmax = 45.3 %, Tmin = 0.25 %, Dmax = 2.70, and Dmin = 0.34, Rd = 7.94,
EP = 99 %).
4. Computational details
4.1 Geometric Structure of (E)-4-(phenyldiazenyl)aniline
The structural energy minimization calculation was carried out using the program HyperChem
08 by molecular mechanics (MM+). The obtained structure was fully optimized by DFT
calculations with a hybrid functional B3LYP (Becke's three parameter hybrid functional using
LYP correlation functional) and PBE1PBE (Perdew, Burke and Enzerhof GGA exchange-
correlation functional) at 6-31G, 6-31G*, 6-31+G*, 6-31++G* basis sets (Fig. 3). To account
Fig. 3 Optimized molecular structure of the (E)-4-(phenyldiazenyl)aniline calculated by B3LYP/6-31G method.

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solvent effect the IEFPCM (Integral Equation Formalism PCM) method coupled to UAKS radii
was used. The Integral Equation Formalism PCM, by Cances, Mennucci and Tomasi is the most
popular PCM version. It employs a molecule shaped cavity composed of spheres centered on the
nuclei, while the reaction field is modeled by placing charges on the cavity surface [25]. All
density functional calculations were performed with the Gaussian 09W software package and
Gauss view 05 visualization programs [26].
4.2 Electronic Structure and Excited States of (E)-4-(phenyldiazenyl)aniline
Theoretical absorption spectra of the title molecule optimized in solvents (DMF and Water) were
calculated using TDB3LYP/6-31G, TDB3LYP/6-31G*, TDB3LYP/6-31+G* and TDB3LYP/6-
31++G*, TDPBE1PBE/6-31G, TDPBE1PBE/6-31G*, TDPBE1PBE/6-31+G*, TDPBE1PBE/6-
31++G* methods. To account solvent effect Polarized Continuum Model (PCM) was used.
(a)
(b)
(c)
Fig. 4 Calculated (a – in DMF, b – in Water) and c – experimental (in DMF) UV/Vis spectrum of the (E)-4-
(phenyldiazenyl)aniline

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The theoretical UV/Vis spectra (in DMF and Water) show that the title molecule is not very
sensitive to solvents (Fig. 4 a,b,c). The equations were solved for 20 excited states, where the
computational studies were performed using the IEFPCM (Integral Equation Formalism PCM)
method coupled to UAKS radii. The TDDFT method is able to detect accurate absorption
wavelength at a relatively small computing time, which corresponds to electronic transitions
computed on the ground state geometry (Table 1). Experimental UV/Vis spectrum of the (E)-4-
(phenyldiazenyl)aniline in DMF at concentration 3.5·10–4 M/l and temperature 21 °C is
presented in Fig. 4 c.
Table 1 Electronic absorption spectrum of the (E)-4-(phenyldiazenyl)aniline calculated by TDB3LYP/6-31G
method
Excited Wavelength
Excitation
Energy (eV)
2.48
Configurations Composition
(corresponding transition orbitals)
0.71(H-1→L)
Oscillator
Strength (f)
0.00
State
S1
(nm)
501
S2
402
3.08
0.71(H→L)
1.05
0.57(H-3→L) + 0.35(H-2→L) - 0.10(H→L+1)
+ 0.17(H→ L+2)
0.63(H-4→L) - 0.13(H-2→L)
- 0.24(H→L+1) - 0.12(H→ L+2)
0.16(H-4→L) - 0.32(H-3→L) + 0.57(H-2→L)
+ 0.19(H→L+3)
S3
S4
S5
297
293
279
4.17
4.24
4.45
0.01
0.00
0.06
S6
S7
S8
S9
S10
259
254
249
248
230
4.79
4.89
4.98
5.00
5.40
0.27(H-4→L) + 0.56(H→L+1) + 0.30(H→L+2)
- 0.2(H-3→L) - 0.31(H→L+1) + 0.59(H→L+2)
0.71(H→L)
0.13
0.06
0.00
0.00
0.00
+ 0.17(H-1→L+2)
+ 0.17(H-1→L+3)
0.15(H-5→L) + 0.11(H-4→L+1) - 0.14(H-2→L)
+ 0.64(H→L+3)
S11
S12
S13
223
211
204
5.56
5.87
6.09
0.00
0.04
0.02
0.64(H-5→L) - 0.16(H→L+3) - 0.20(H→L+4)
- 0.24(H-3→L+2) - 0.32 (H-3→L+3) - 0.32(H-2→L+1)
+ 0.42(H-2→L+2) - 0.11(H-2→L+3)
0.10(H-8→L) + 0.12(H-7→L) + 0.66(H-6→L)
- 0.14(H-1→L+4)
- 0.28(H-7→L) + 0.17(H-6→L) + 0.62(H-1→L+4)
- 0.22(H-3→L+1) + 0.55(H-2→L+1) + 0.34(H-2→L+2)
- 0.13(H→L+4)
S14
S15
S16
201
199
198
6.18
6.24
6.26
0.00
0.00
0.00
0.15(H-5→L) + 0.19(H-4→L+1) - 0.12(H-3→L+2)
+ 0.11(H-2→L+1) - 0.61(H→L+4)
0.63(H-7→L) + 0.30(H-1→L+4)
0.60(H-3→L+1) + 0.26(H-3→L+2) - 0.11(H-3→L+3) +
0.13(H-2→L+1) + 0.18(H-2→L+2)
S17
S18
S19
S20
196
195
191
188
6.34
6.36
6.47
6.59
0.00
0.00
0.01
0.00
- 0.36(H-4→L+1) - 0.60(H-4→L+2)
*H-HOMO, L-LUMO
The experimental absorption spectrum of the title compound (Fig. 4 c) has a wide absorption at
about 350-485 nm which characterized by maximum at 399 nm and calculated spectrum in DMF

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(Fig. 4 a) shows the highest oscillation in 402 nm at f = 1.05. The strong peak at 402 nm is due to
the Charge-Transfer (CT) excited state. The other peaks are local excited states corresponding to
electrons going into anti-bonding orbitals associated with the benzene rings. Excitation of one
electron at 402 nm belonged to the transition into the excited singlet state S2 (S0→S2) and
describes by a wave function corresponding to configuration for one-electron excitation (52
(HOMO)→53(LUMO)) (Fig. 5). The other excited states have very small intensity (f ≈ 0): these
transitions are nearly forbidden by orbital symmetry considerations (Table 1).
(53) LUMO
(52) HOMO
Fig. 5 Form of the MO involved in formation of absorption spectrum of the (E)-4-(phenyldiazenyl)aniline at λmax
=
402 nm.
The results of calculations of electronic spectrum of the (E)-4-(phenyldiazenyl)aniline in DMF
and Water with different methods and basis sets (using TDB3LYP/6-31G, TDB3LYP/6-31G*,
TDB3LYP/6-31+G* and TDB3LYP/6-31++G*, TDPBE1PBE/6-31G, TDPBE1PBE/6-31G*,
TDPBE1PBE/6-31+G*, TDPBE1PBE/6-31++G*) show that TDB3LYP/6-31G method is better
than the other methods that predicts changes in the absorption spectrum of the title molecule
(Fig. 4 a,c). In the work are presented results of calculations of geometry optimization and
absorption spectrum calculated by B3LYP/6-31G and TDB3LYP/6-31G. We found that addition
of diffusion and polarization functions increases electron density of small atoms and distorts
electron spectrum of the (E)-4-(phenyldiazenyl)aniline [10,11].
4.3 (E→Z) isomerization of the (E)-4-(phenyldiazenyl)aniline
In order to study (E→Z) isomerization of the (E)-4-(phenyldiazenyl)aniline, experimental
UV/Vis spectrum of solution of the (E)-4-(phenyldiazenyl)aniline in DMF after 1 h. UV
radiation was recorded (Fig. 6). As seen from Fig. 6 after 1 h. UV radiation character of the
curve (2) did not change. E and Z isomers of the 4-(phenyldiazenyl)aniline absorb light at λmax
=
399 nm. Optical density decreases from 2.0 (curve 1) to 1.8 (curve 2).

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Fig. 6 Experimental UV/Vis spectrum of solution containing the 4-(phenyldiazenyl)aniline in DMF: (1) – E isomer
before UV radiation, (2) – Z isomer after 1 h. UV radiation
Then for investigation of (E→Z) isomerization (Fig. 7) in PVA matrix PVA-film containing (E)-
4-(phenyldiazenyl)aniline was prepared according to 2.1.
Fig. 7 (E→Z) isomerization of the (E)-4-(phenyldiazenyl)aniline
The absorption spectrum of the sample was recorded after 0.5; 1.0; 2.5 and 4.0 h. after beginning
of UV radiation. During the exposure, the distance between the light source and the sample was
25 cm, while the temperature of the sample was 20-22 °C. As seen from Fig. 8 the peaks of
absorption do not change (λmax = 399 nm). Over time (curves 2,3,4,5) the optical density of the
sample begins to decrease (for curve 3: D = 0.90, for curve 4: D = 0.68 and for curve 5 D =
0.44). It is indicated that initial PVA-film containing (E)-4-(phenyldiazenyl)aniline (curve 1)
transfers to (Z)-4-(phenyldiazenyl)aniline (curve 5) after four h. UV radiation (Fig. 8).

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Fig. 8 Experimental UV/Vis spectrum of film containing (E)-4-(phenyldiazenyl)aniline (1) – Initial film before UV
radiation, (2) – after 0.5 h., (3) – after 1 h., (4) – after 2.5 h. and (5) – after 4.0 h. UV radiation.
In order to confirm the correctness of our findings IR-spectroscopy was used. IR-spectra of
PVA-film were recorded before and after 2.5 h. and 4 h. UV radiation (Fig. S1a,S1b,S1c).
Comparison of the IR-spectra of the (E)-4-(phenyldiazenyl)aniline and (Z)-4-
(phenyldiazenyl)aniline has shown a small change in the absorption in region 3000-3500 cm-1.
IR-spectrum of PVA-film before UV radiation has absorption at 3322.59 cm-1 (Fig. S1a) but in
PVA-film after 2.5 h. (Fig. S1b) and 4 h. (Fig. S1c) UV radiation has absorption at 3307.03 cm-1
and 3291.13 cm-1 respectively. The change of absorption related to νC-H in (E)-4-
(phenyldiazenyl)aniline and (Z)-4-(phenyldiazenyl)aniline respectively.
4.4 Anisotropy of thermal conductivity of PVA-films containing the (E,Z)-4-
(phenyldiazenyl)aniline
During (E
→Z) isomerization many properties of the system changes like refractive index,
solubility, viscosity and thermal and electrical conductivity [27]. In the present study, we have
studied thermal conductivity of the PVA-(E) isomer and PVA-(Z) isomer systems. This method
was described in [27]. Thermo-physical properties of films was determined by thermal

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conductivity of samples in parallel (λ||) and perpendicular (λ ) directions of stretching axis.
During this work, it was established that the oriented PVA-film has the phenomenon of
anisotropy of thermal conductivity (λ|| / λ ). Thermal conductivity in a direction of orientation
(λ||) is higher than in a direction perpendicular orientations (λ ). On resulting anisotropy at a
known degree of extension it is possible to judge anisotropy of chain structure. It has been
noticed that during thermal expansion and thermal conductivity geometric parameters of
molecule, intermolecular forces play a significant role. In unstretched PVA-film anisotropy of
thermal conductivity is not observed appreciably (λ|| = 0.875 W/m.°C; λ = 0.869 W/m.°C)
whereas in stretched PVA-film anisotropy of thermal conductivity is observed clearly (Table 2).
Table 2 Dependence of thermal conductivity on stretching degree in pure PVA-films
λ, W/ m.ºC
λ , W/ m.ºC
Rs
λ||, W/ m.ºC
0.875
λ|| / λ
1.00
1.15
1.38
1.60
1.75
1.86
0.872
1.0
1.5
2.0
2.5
3.0
4.0
0.876
0.878
0.880
0.881
0.764
0.636
0.549
0.503
0.475
0.882
When we inject the dye in PVA-film there is change in its thermal conductivity (Table 3). It has
been found that along an axis of orientation, it has increased, and in perpendicular axis it is
reduced. Results of thermal conductivity measurements of PVA-films containing the (E,Z)-4-
(phenyldiazenyl)aniline depending on stretching degree are presented in Table 3.
Table 3 Thermal conductivity of PVA-films containing the (E,Z)-4-(phenyldiazenyl)aniline at concentration 0.3
wt.%
λ, W/ m.ºC
λ , W/ m.ºC
0.340
Rs
4-(phenyldiazenyl)aniline
λ||, W/ m.ºC
0.862
λ|| / λ
2.54
2.73
3.40
4.36
3.67
4.51
6.41
8.19
2.0
3.0
4.0
5.0
2.0
3.0
4.0
5.0
(E) isomer
0.849
0.842
0.841
0.865
0.853
0.846
0.835
0.311
0.248
0.194
0.236
0.189
0.132
0.102
(Z) isomer

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The obtained data suggest that in the PVA-(Z) isomer system, anisotropy of thermal conductivity
is stronger than in the PVA-(E) isomer system. We found that at (E→Z) isomerization the Z-
isomer which is less stable (has a larger energy system) has a greater anisotropy of thermal
conductivity as compared with the more stable E-isomer. Theoretical calculation of the full
energies of the (E,Z)-4-(phenyldiazenyl)aniline by DFT/B3LYP/6-31G level of theory leads to
the following values: HF(E isomer) = -627.9655682 Hartree and HF(Z isomer) = -627.9425978 Hartree.
4.5 Anisotropy of electrical conductivity of PVA-films containing the (E,Z)-4-
(phenyldiazenyl)aniline
In the present section, we have studied electrical conductivity of the PVA-(E) isomer and PVA-
(Z) isomer systems. Electrical conductivity of PVA-films was measured on the complex
equipment LC – 201(Alfa Laval Group, Sweden). The PVA-films were placed on the surface of
the thin sheet (electrode) from SnO2 (thickness 70 µm). And then the films were coated with an
aluminum electrode (S = 2.5 cm2). The thickness of the PVA samples was 65 µm. The electrical
conductivity of PVA-films was measured in parallel (δ||) and perpendicular (δ ) directions of
stretching axis. In unstretched PVA-film anisotropy of electrical conductivity is not observed (δ||
= 1.1ꢀ105 S.cm-1; δ = 1.1ꢀ105 S.cm-1) whereas in stretched PVA-film anisotropy of electrical
conductivity is observed very clearly (Table 4).
Table 4 Dependence of electrical conductivity on stretching degree in pure PVA-films
δ, S.cm-1
δ||, S.cm-1
1.1ꢀ105
4.6ꢀ105
9.8ꢀ105
3.6ꢀ106
7.8ꢀ107
6.5ꢀ108
δ , S.cm-1
1.1ꢀ105
8.4ꢀ104
1.7ꢀ104
2.2ꢀ103
5.7ꢀ102
6.1ꢀ101
δ|| / δ
Rs
1.0
1.5
2.0
2.5
3.0
4.0
1ꢀ100
0.5ꢀ101
5.7ꢀ101
1.6ꢀ103
1.3ꢀ105
1.1ꢀ107
After injecting the dye in PVA-film there is change in its electrical conductivity (Table 5). It has
been found that along an axis of orientation, it has increased, and in perpendicular axis it is
reduced. Anisotropy of electrical conductivity of PVA-films was defined as δ|| / δ and is
presented in Table 5.

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Table 5 Electrical conductivity of PVA-films containing the (E,Z)-4-(phenyldiazenyl)aniline at concentration 0.3
wt.%
δ, S.cm-1
4-(phenyldiazenyl)aniline
δ||, S.cm-1
3.2ꢀ105
6.1ꢀ107
9.8ꢀ107
4.6ꢀ108
6.6ꢀ105
7.8ꢀ107
5.6ꢀ108
3.1ꢀ109
δ , S.cm-1
5.6ꢀ104
6.9ꢀ102
5.5ꢀ101
1.2ꢀ101
3.0ꢀ104
3.4ꢀ102
4.9ꢀ101
5.2ꢀ100
δ|| / δ
Rs
2.0
3.0
4.0
5.0
2.0
3.0
4.0
5.0
5.7ꢀ100
0.9ꢀ105
1.8ꢀ106
3.8ꢀ107
2.2ꢀ101
2.3ꢀ105
1.1ꢀ107
0.6ꢀ109
(E) isomer
(Z) isomer
The obtained data suggest that in the PVA-(Z) isomer system, anisotropy of electrical
conductivity is stronger than in the PVA-(E) isomer system. At (E Z) isomerization we found
→
that the isomer which is less stable (has a larger energy system) has a greater anisotropy of
electrical conductivity as compared with the more stable isomer.
5. Conclusions
In the present work electronic structure, trans-cis isomerization, polarization properties of 4-
(phenyldiazenyl)aniline in PVA-matrix via theoretical and experimental investigations were
studied. On the basis of PVA and (E)-4-(phenyldiazenyl)aniline PVA-polarizer for UV and Vis
regions of spectrum was created. In spectral range 353-466 nm PE is 90 %. In the region 386-
447 nm PE = 98-99 %. The results of calculations of electronic spectrum of the (E)-4-
(phenyldiazenyl)aniline in DMF with different methods and basis sets (using TDB3LYP/6-31G,
TDB3LYP/6-31G*, TDB3LYP/6-31+G* and TDB3LYP/6-31++G*, TDPBE1PBE/6-31G,
TDPBE1PBE/6-31G*,
TDPBE1PBE/6-31+G*,
TDPBE1PBE/6-31++G*)
show
that
TDB3LYP/6-31G method is better than the other methods that predicts changes in the absorption
spectrum of the title molecule. PVA-film before and after UV radiation has the same absorption
spectra. The peaks of absorption do not change (λmax = 399 nm). In the PVA-(Z) isomer system,
anisotropy of electrical and thermal conductivity is stronger than in the PVA-(E) isomer system.
PVA-(Z) isomer which is less stable (HF(Z
= -627.9425978 Hartree) has a greater
isomer)
anisotropy of electrical and thermal conductivity as compared with the more stable PVA-(E)
isomer (HF(E isomer) = -627.9655682 Hartree). There is relationship between optical and electrical
anisotropy and anisotropy of thermal conductivity of PVA-films. Anisotropy of optical, electrical
and thermal conductivity occurs only in stretched PVA-films.

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Highlights
ꢀ Polarization, Excited States, Trans–Cis (E→Z) Isomerization Properties of
4-
(phenyldiazenyl)aniline
ꢀ DFT, UV/Vis, IR-Spectroscopic Determination of 4-(phenyldiazenyl)aniline
ꢀ Solvent effect on the absorption spectrum
ꢀ HOMO-LUMO, excitation energies and oscillator strengths for E and Z isomers of the 4-
(phenyldiazenyl)aniline
ꢀ Optical Properties of the PVA-films containing 4-(phenyldiazenyl)aniline