Thickness dependant Electro-Optical studies on KBr, Na2SO4 and Bio-
Molecular Aloe vera doped Polystyrene Polymer film Composites.
K. K. Kamani*,H.Gopalappa . A.B. Banakar, R.K Rang swami
Department of PG Studies, Government Science College. Chitradurga
Karnataka, INDIA
Received: / Accepted: / Published
.
Abstract: Today the waste plastic material has become a serious problem.
Polystyrene complexes are biodegradable and well known biomedical
environmental friendly synthetic polymer. Polystyrene loses its mechanical
and tensile properties due to effect of UV light and heat. UV light induces
the production of free radicals by oxidation. Free radicals cause the
chains of polymer to breakdown. Polystyrene is a vinyl polymer, which make
up a large family of polymers that are made from vinyl monomers containing
C=C bonds. Present studies reports the Polystyrene polymers mixed with the
inorganic metal complexes like KBr, Na2SO4 and bio molecule Aloe vera. The
prepared film samples of thickness around 0.545mm were characterized using
UV-visible, ATIR & electrical studies like conductivity and dielectric
measurements. The UV visible absorption studies of complex matrix films
indicated the different optical levels for different dopants. These optical
transitions create charge transfer complexes leading to the increase in
carrier concentration. The dielectric properties and electrical
conductivity of the samples are measured. The Polystyrene Polymer C=C bonds
breaks with the bioactive dopants and exhibiting the property of
biodegradable. The Polystyrene Polymer film matrixes with motioned dopants
may find applications in the environmental friendly products.
Key words: Polymer thin films, Electrical studies, Optical studies,
Polystyrene complexes, Polymer composites
1. Introduction
(Polymeric materials are the back bone of the present life. The polymers
generally display rich variety in their morphology. The generous
productions are creating environmental hazardous conditions and pollution
problems. At this critical situation the orientation about biodegradable,
recycling profession is quite essential. Polymeric material with a
biomolecule is used for the manufacture of biosensors, bioreactors and in
the medical field. Biomedical containers or its optical transparency,
durability and cost effectiveness, inert nature and no toxicity.
Polystyrene packaging products are discarded in dumps, landfills or simple
litter after their useful application.
In the emerging polymer science greatest attention has been paid to
determine the conductivity of different solutions at various
concentrations. The required properties can be tailored by adding the
dopant concentrations in the polymer molecular matrix. The excellent
physical and processing properties make polystyrene suitable for a lot of
applications than any other plastic. This is used in packaging, laboratory
ware and electronics for protective packaging in electrical, pharmaceutical
and retail industries because of its light weight, shock resistance and
cushioning properties [1-3]. Polystyrene losses its mechanical and tensile
properties due to the effect of UV, IR light and heat. UV light induces the
production of free radicals by oxidation. Free radicals cause the chains of
polymer to breakdown. The excellent physical and processing properties make
Polystyrene suitable for a lot of applications than any other plastic
material. This induces the changes in the physical and chemical
properties. Indirectly the thermal, electrical and optical properties [2-
4]. Conducting polymers exhibit a wide range of novel electrochemical and
chemical properties that has led to their use in a diverse array of
applications including sensors. Polymeric material with a bio molecule is
used for the manufacture of biosensors, bioreactors and in the medical
field. [5-6], switchable membrane[7], anti-corrosive coatings [8-
9],biosensors[10],electro chromic devices [11] and rechargeable batteries
[12-13]. Like Polyaniline, polystyrene is one of the most promising
candidates for industrial application of conducting bio polymers [14-15].
2. Experimental Section
When a polymer matrix is mixed with inorganic materials the thermal,
mechanical, optical, electrical, and magnetic and flammability properties
of such a composites are much different from the pure polymer matrix
itself. The thermoplastic polymer polystyrene crystals were obtained from
Sd fine chemicals, Mumbai, India. The Polystyrene crystals of 0.85grms and
inorganic dopants (0.15grms) like aloevera, KBr, Na2SO4 mixed uniformly and
placed in a film preparation dies of the equipment model PF-A-15. Set the
temperature of plates to the melting temperature of the samples and place
the weighed polymer granules ( 20-25 granules) in the dies. Switch on the
temperature control unit for the sample well below the melting temperature.
When the temperature reaches the maximum point as set in the control unit
tight & rotate the knob of the die, then apply pressure nearly 8-10
tones. Switch off the pressure knob and maintain the same pressure for 1 to
2 minutes, then switch off the temperature control unit & release the water
slowly to flow through the plates as condenser. When the temperature
reaches 400_450 release pressures by removing pressure knob, The as
prepared film samples of thickness around 0.545mm were characterized using
UV-visible, ATIR techniques. The electrical studies like conductivity and
di-electric measurements were undertaken on the film samples using
impedance analyzer model HIOKI 3532-50 LCR HiTESTER.
3. Results and Discussion
3.1 UV-Visible studies
The aim of most of these investigations was to describe the dependence
of UV visible and infrared characteristics in terms of the stereo regular
nature of polymer chain.
Figure 1. The absorption verses wavelength.
Figure 1 shows the UV-Visible absorption peaks for KBr, Na2SO4, & aloe
vera, which shows shift in wave length. The shift in wavelength for aloe
vera is almost same as that of pure polystyrene. But the shift in
wavelength is more for KBr & Na2SO4.The table 1 below shows the clear
variations and comparison of the absorption peaks.
Table 1
"Name "Peak 1 "Peak 2 "
"Pure "273.611728"291.337183"
"Polystyren"nm "nm "
"e (P2) " " "
"P2+Na2SO4 "341.248334"370.635273"
" "nm "nm "
"P2+KBr "339.848956"369.235895"
" "nm "nm "
"P2+aloe "276.565971"292.736562"
"vera "nm "nm "
Figure 2. Plot of (αhν)1/2 verses hν.
The optical energy band gap is determined by translating the UV–visible
spectra into Tauc's plot using the frequency dependent absorption
coefficient α(ν) given by Mott and Davis
where, α(ν) = 2.303A/d (A is the absorbance and d is the film
thickness), h is Planck's constant, ν is the frequency of the incident
photons, β is a constant, Eg optical energy band gap and r = 2 is empirical
index, valid for indirect allowed transitions . A plot of (αhν)1/2 verses
hν is shown in figure 2, which shows a linear behavior Extrapolation of
this linear portion of the curve to zero absorption gives the optical
energy band gap Eg [22]. The energy band gap values for the pure
polystyrene and the corresponding composites such as polystyrene + aloe
vera, Polystyrene + Na2SO4, and Polystyrene + KBr of same thickness 0.545mm
are listed in the table 2.
Table 2
"NAME "BAND GAP "
"Pure "1.3420719 eV "
"polystyrene " "
"P2 with aloe "1.17943136 eV "
"vera " "
"P2 with KBr "1.2963671 eV "
"P2 with "1.24131497 eV "
"Na2SO4 " "
The doping in different thicknesses alters the optical properties &
electronic nature creates defects levels. The presence of defects such as
anions, cat ions, radicals, organic species etc may result in the formation
of new energy levels within the polymer. The origin and variation of these
optical band gaps suggests that the doping concentration modifies the
electronic structure of the inorganinic salts doped Polystyrene and
creates defect level within the band gap.[20-21] The decrease in band gaps
with doping concentration may be attributed to the creation of point
defects that existed within the band gap by the creation of charge transfer
complexes (CTC).
3.1 ATR-IR studies
ATR uses a property of total internal reflection resulting in an
evanescent wave. A beam of infrared light is passed through the ATR crystal
in such a way that it reflects at least once off the internal surface in
contact with the sample, which enables samples to be examined directly in
the solid or liquid state without further preparation. The penetration
depth into the sample is typically between 0.5 and 2 micrometers, with the
exact value being determined by the wavelength of light. This evanescent
effect only works if the crystal is made of an optical material with a
higher refractive index than the sample being studied. The ATR studies
undertaken on the present polystyrene composites are shown in the figure 3.
Figure 3. ATR studies on the polymer composites.
"Polystyren"Type of bonds "
"e " "
"3554.41cm-"O-H Stretching "
"1 "variation "
"2966.96cm-"Asymetric stretching "
"1 " "
"1745.98cm-"C=C stretching "
"1 "vibration "
"1260.62cm-"C-H wagging "
"1 " "
"750.21 "Skeletal peak "
"cm-1 " "
"650.90 "Out of plane vibration "
"cm-1 " "
Table 3.1
Table 3.2
"Polystyrene "Type of bonds "
"+ Aloe vera " "
"3620.31 cm-1"O-H Stretching "
" "variation "
"3020.57 cm-1"Asymmetric stretching "
"1600.13 cm-1"C=0 stretching "
" "vibration "
"1245.45 cm-1"C-H wagging "
"751.02 cm-1 "O-H Stretching "
" "variation "
"620.93 cm-1 "Skeletal peak "
Table 3.3
"Polystyrene "Type of bonds "
"+KBr " "
"3620.16 cm-1 "O-H Stretching "
" "variation "
"3161.18 cm-1 "Asymmetric "
" "stretching "
"1495.12 cm-1 "Bending of CH2 "
" "vibration "
"1154.43 "C-O stretching "
"739.60 cm-1 "Skeletal peak "
"620.23 cm-1 "Out of plane "
" "vibration "
Table 3.4
"Polystyriene+ "Type of bonds "
"Na2So4 " "
"3619.96 cm-1 "O-H Stretching "
" "variation "
"3161.16 cm-1 "Asymmetric "
" "stretching "
"1599.5 cm-1 "C=0 stretching "
" "vibration "
"1181.37 cm-1 "C-H wagging "
"696.25 cm-1 "Skeletal peak "
"619.33 cm-1 "Out of plane "
" "vibration "
The recorded tables 3.1, 3.2, 3.3 and 3.4 indicates the observed bonds
in the complex structures of bio degradable nature of Polystyrene complex
with the salts like Na2SO4, KBr and useful herbs like Aloe vera [24].
3.3 Dielectric and Electrical conductivity studies
Conductivity (G), the inverse of resistivity (R) is determined from the
voltage and current values according to Ohm's law.The polymers, unlike in
the conductor and semiconductor, contain no free charge carriers that can
move in the presence of electric field to conduct current. DC conductivity
by achieving mobility through the micro-Brownian motion of polymer
segments. The electrical conduction in polymers is highly dependent upon
the structural disorder arising from the purity, dimensions, and aging.[19-
20] The electronic polarization occurs as result of the displacement of
positively charged nucleus and the negatively charged electrons of an
doping Na2So4, Kbr, & alovera atoms in opposite directions on
application of an electric field. Choosing a dielectric material continues
to be an exercise in trying to find a high-k dielectric film with
electrical, [18-19] thermal and mechanical properties comparable to or
better than those of SiO2. Specific conductance is the reciprocal
quantity, and measures a material's ability to conduct an electric current.
It is commonly represented by the σ (sigma), but κ (kappa) (especially in
electrical engineering) or . Its SI unit is siemens per metre (S m 1) and
CGSE unit is reciprocal second (s 1). The electrical resistivity ρ ratio
of the electric field to the density of the current
ρ is the resistivity of the conductor material (in Ωm), E is the
magnitude of the electric field (Vm 1). Dielectric substances consist of
molecules of two atoms held together by ionic bonds formed by the sharing
of electrons of one atom by another. The application of an external
electric field to such substance tends to displace the positive ion
relative to the negative ion thereby inducing a dipole moment in the
molecule. The conductivity and resistance of the studied polymer composites
are shown in the figure 4 and figure 5 respectively.
Figure.4. Variation of conductivity with frequency.
Figure.5. Variation of resistance with frequency.
Conductivity increases with increasing frequency and all the samples
shows maximum conductivity at the applied frequency of 4x106 Hertz &
declines suddenly. Whereas pure does not shows any increase in
conductivity with increasing frequency but suddenly increases at the
frequency 4x106 Hertz is exactly apposite nature to the doped samples.
The KBr stands at the top & Na2SO4 greater to the Alovera which is a least
comparatively. It is observed that the all the samples shows exponential
decrees of the resistance from the 30x106 Ohms to the lowest in the
frequency range 100-1000Hz. Resistance has decreased and as a result
inductive effect and capacitive effect have become more prominent.
Figure 6. Graph of comparative loss factor.
Figure 7. Graph of comparative dielectric loss.
Dielectric comparative loss factor and dielctric loss of the studied
polymer composites are shown in the figure 6 and figure 7 respectively. The
loss factor of Aloe era shows little variation as compared to pure
polystyrene [21-23] whereas for KBr and Na2SO4, shows more alterations.
Dielectric loss for aloe vera [24] are increases and slowly decreases with
the frequency, whereas for KBr and , Na2SO4, shows sudden decline.
4. Conclusions
The Polystyrene molecular matrix with KBr, Na2SO4 and Aloe vera
dopants forms the charge transfer complex. The charges increase with the
increase of dopant percentage. Optical abosrptions of Polystyrene
composites are dominent at the lower values and shift in wavelength
describes the energy conversion. The Polystyrene polymer matrix behaves
as the good conducting polymer with suitable dopnats The UV optical
absorption and increase in optical band gaps of Polystyrene with aloe vera
suggests the biosenstivity. The Polystyrene with these dopants forms the
Charge Transfere Complexes [CTC] and free radicals causing the chains of
polymer to breakdown. The doping in different thicknesses alters the
electronic properties & creates defects levels. The presence of defects
such as anions, cations, radicals, organic species etc may result in the
formation of new energy levels within the polymer. The dielectric loss and
electrical conductivities suggests that molecular orientations and dipole
moments in the Polystyrene complexes. The required properties can be
tailored by adding the various dopant concentrations in the Polystyrene
polymer molecular matrix.
Acknowledgment
The author (KKK) is grateful to the UGC and Government of Karnatak for
their kind cooperation and moral support.
References
1] J. McCallum, C. Vincent, Polymer electrolytes review-1, London:
Elsevier; 1987, vol. 173.
2] J. Donoso, T. Bonagamba, Panepucci H, Oliveira L, Gorecki W, C. Berthier
and M. Armand, J Chem Phys 1993;98:10026.
3] E. Tsuchida, Kobayashi N, Ohno H. Macromolecules 1988; 21:96.
4] KKKamani.V.Ravidrachery, Ismyil, R.F Bahjentri, A.Harish,S. Ganesh
WJOE, 2010 Volume 7[3] P525.
5] R.F. Bhajantri, V. Ravindrachary, A. Harisha, Vincent Crasta, Suresh P.
Nayak, Boja Poojary, Polymer, 2006, vol 47, 3591–3598.
6] Tanu Sharma, Sanjeev Aggarwal, Shyam Kumar, V. K. Mittal, P. C. Kalsi,
V. K. Manchanda, J Mater Sci, 2007, 42,1127–1130
7] Magda M I Khalil, G M Nasr and Naeem M El-Sawy, J. Phys. D: Appl. Phys.
2006, 39 5305–5309
8] Lewis TW, Smyth MR, Wallace GG. Analyst 1999;124:213.
9] Mirmohseni A, Oladegaragoze A. J Appl Polym Sci 2002;85:2772.
10] Tallman DE, Spinks GM, Dominis A, Wallace GG. J Solid State Electro
chem. 2002;6:73.
11] Spinks GM, Dominis AJ, Wallace GG, Tallman DE. J Solid State Electro
chem. 2002;6:85.
12] Smyth MR, Zhao H, Wallace GG. Trends in Anal Chem 1999;18:245.
13] Sapp SA, Sotzing GA, Reynolds JR. Chem Mater 1998;10:2101.
14] Munstedt H, Kohler G, Mohwald H, Naegele D, Bitthin R, Ely G,Meissner
E. Synth Met 1987;18:259.
15] Osaka T, Naoi K, Ogano S. 1988: 185(5): 1071.
16] Baird ME 1968 Rev. Mod. Plzys.1973, 40, 219.
17] Electrical Properties of Polymeric Materials (London: Plastics
Institute) IBM 1970.
18] McCrum et al. (1967) and in articles by Baird (1968, 1973)
19] R. Chau, J. Brask, S. Datta, G. Dewey, Mark Doczy, Brian Doyle, Jack
Kavalieros, B Engineering. 2005, 80(1) 1-6. en Jin, Matthew Metz, A.
Mazumdar and M. Radosavljevic, Microelectronic
20] KKKamani, V. Ravindrachaery, R, F. Bajanri Ismyil,WJOE-2009, 6, P-455.
21] KKKamani, V.Ravindrachaery Ismyil, R,F Bajanri, A Harish,S Gnash
,WJOE,2008 5[3] P-326327.
22] L. Smith et. al, "Exploring the Limits of Stress-Enhanced Hole
Mobility", IEEE Electron Device Letters, Sept 2005, vol 26, no. 9.
23] P.K. Khare, M.S. Gaur, R. Singh, Ind. J. Phys. 1994; 68A: 545.
24] "Taxon: Aloe vera (L.) Burm. f.". Germplasm Resources Information
Network, United States Department of Agriculture. .http://www.ars-
grin.gov/cgi-Aloe%20vera.
Corresponding author: Kamani.K.K. Professor in physics / MSc, FSES, BEd.
Polymer Nano and Micro researcher. E-mail:
[email protected]
-----------------------
