Incorporation of Acetoacetanilide Crystals in Host PMMA Polymer Matrix and Characterizations of the Hybrid Composite

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Journal of Minerals & Materials Characterization & Engineering, Vol. 11, No.5, pp.519-527, 2012

519

Incorporation of Acetoacetanilide Crystal s in Host PMMA Polymer Matrix

and Characterizations of the Hyb rid Composit e

Sharada G. Prabhu1* and B.Manjunatha Pattabi2

1Dept. of Physics NMAM Institute of Technology, Nitte- 574 110, India.

2Dept. of Materials Science, Mangalore University, Mangalagangotri- 574 199, India.

*Corresponding author e-mail [email protected].

ABSTRACT

Blending of polymer with organic/inorganic material has given a new direction for developing

novel materials. This is an easy and inexpensive method of modifying various properties of the

individual materials and composites. The aim of the present work is an attempt to incorporate

crystals in polymer host and investigate the effect, on optical properties of the of polymer-

crystal combine. In this paper a novel technique of incorporating inorganic/organic crystal in a

host polymer matrix is reported. Crystals of acetoacetanilide (AA) are grown in the host Poly

Methyl Methacrelate (PMMA) by simple evaporation technique. The scanning electron

micrograph (SEM) studies reveal the growth of Acetoacetanilide crystals of varying sizes and

shapes (flakes) in prepared samples. The results are confirmed by various spectroscopic

characterization studies such as X-ray diffraction (XRD), Fourier Transform Infrared

Spectroscopy (FT-IR) and the UV-Vis spectroscopy. The investigations carried out, show a

change in optical absorption band edge which is attributed due to change in band gap because

of crystal sizes.

Key words: Polymer composite, Optical properties, PMMA-acetoacetanilide composite, Nano

composites, Spectroscopic techniques.

1. INTRODUCTION

Inorganic/organic hybrid materials have attracted increasing interests due to their unique optical

and electronic properties [1-6]. Organic crystals have a narrow transparency and exhibit low

thermal and mechanical resistance. It is established that the polymers are excellent host

520 Sharada G. Prabhu and B.Manjunatha Pattabi Vol.11, No.5

materials. When the nano-particles are embedded or encapsulated in polymer, the polymer acts

as surface capping agent. In addition, the particle size is controlled well within the desired

regime. For application in opto-electronics and electronics, the control of particle size and their

uniform distribution within the polymer is the key to technology based on the nano-particles in

polymers. With these advantages of organic cr ystal and polymer, a new approach, the growth of

organic crystals in polymer matrix has been contemplated. This approach is intended to combine

the properties of both classes of material that is the organic acetoacetanilide and the polymer

PMMA. The authors herein describe the technique of incorporating acetoacetanilide crystals in

PMMA m atrix and to st udy th e effect on the optical propert ies o f acetan ilide crystals due to the

presence of the host PMMA. Various spectroscopic and morphological techniques are useful in

characterizing the nano-composites. In the present paper the preparation, characterisation of the

nano-composites and the effect on optical properties of acetoacetanilide crystals due to the

presence of polymer matrix have been reported. The results are demonstrated by X-ray

diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and the UV-Vis

spectroscopy and scanning electron microscopy (SEM) studies.

2. EXPERIMENTAL

2.1 General

Research grade Acetoacetanilide and PMMA from Merck are used to prepare the composites.

Using JEOL JD8p Visual XRD, (with automation software:VISX122D), with cu Kα of -λ=

1.5405 Ǻ (30KV) as a source, the Xrd data has been recorded. The FT-IR spectroscop y analysis

has been carried out using Nicolet AVATAR 330 FT-IR instrument in the wave number range

from 400cm-1 to 4000cm-1. Shimadzu UV-Vis –NIR Spectrophotometer model 3101 PC has b een

emplo yed fo r UV-Vi s m easu rem en ts . JEOL JSM- 5800 LV scanning electron microscope (SEM)

has been used to obtain the microimages of the crystals-polymer composites.

2.2 Preparation of Acetoacetanilide-PMMA Co mp o s it e s

The res earch grad e mate ri als o f aceto acetan ilid e a nd PM MA have be en p rocu red fro m M erk an d

Co. To prepare the PMMA solution 10gm of PMMA is dissolved in 20 ml of double distilled

water. A homogeneous transparent solution of PMMA is obtained after the solution is stirred

continuously at room temperature for 6-8 hours. Then 5 ml of PMMA solution is taken in a

beaker. A saturated solution of acetoacetanilide in chloroform is prepared and filtered. 5 ml of

the filtered solution is mixed with the polymer solution in the beaker and stirred to obtain a

uniform and homogeneous mixture. The blend is obtained by casting the prepared mixture into

a glass petri dish and left for slow evaporation. The resulting thin sheet of acetoacetanilide and

PMMA combined obtained (PM-AA), peels off the petri dish when completely dried. Two

Vol.11, No.5 Incorporation of Acetoacetanilide Crystals 521

samples of the PM-AA blend have been prepared by changing the concentration of

acetoacetanilide ( 10 ml for the first sample and 15 ml for the second sample).

3. RESULTS AND DISCUSSIONS

3.1 XRD Analysis

The Xray diffraction scan is a useful tool to examine the influence of PMMA contents on the

crystalline structure of acetoacetanilide. From the Xrd data recorded, the Xrd spectrograph for

pure PMMA, acetoacetanilide and the composites acetoactanilde-PMMA (PM-AA1 and PM-

AA2) is shown in the Figure1.

From the fig. 1 it is clear that for the prestine acetoacetanilide (AA) the diffraction peaks

observed at 80 (2θ) is due to crystalline structure of acetoacetanilide. Pure PMMA exhibits an

amorphous feature which is characterized by a hump at 16 degrees (2θ) with no sharp peaks.

From the diffraction scans of the samples it is found that

• Amorphous hump is prominent in the sample of PM-AA1

• A decrease in the relative intensity of peaks appearing at 8 degrees is observed in the

samples of PM-AA1 and PM-AA2. This is attributed to the complexation of the PMMA-

acetoacetanilide blend.

Fig. 1 XRD spectrograph patterns of the composites

522 Sharada G. Prabhu and B.Manjunatha Pattabi Vol.11, No.5

The peaks in Xray diffraction patterns of the PM-AA combined are well in agreement with that

of acetoacetanilide. More peaks are observed in the prepared composite PM-AA2 than the

pristine acetoacetanilide. This may be due to the presence of crystals of bigger sizes and

orientation. In the XRD pattern of PM-AA1, broadening of peaks is seen. This is attributed to

the presen ce of t he cr ystal lites of smal ler si zes. Large inten sit y peaks and the in crease i n 7-8].the

number of peaks observed in the sample of PMAA-2 are correlated to a high degree of

orientation [

3.2 FT-IR Studies

The FT-IR spectrographs of PMMA-AA composites are depicted in Fig. 2.

Fig. 2 FT-IR of PM-AA composites

In the spectra of the PM-AA blend characteristic absorption bands have been identified and

assigned, by comparison with the pristine acetoacetanilide and P MMA. T hes e band s are l ist ed in

the table 1. The details of functional groups of PMMA are a sharp intense peak at 1731 cm-1

appeared due to the presence of ester carbonyl group stretching vibration. The broad peak

ranging from 1260-1000 cm-1 is owing to the bending of C-O stretching vibration. The stretching

vibration is shown by the presence of a broad peak between 3100-2900 cm-1. In spectra of

acetoacetanilide the absorption peak appearing at 1650 cm-1 is due to NH bending and the CH

bending at 1425 cm-1. The IR spectra of the PM-AA composites (Sample 1 and Sample 2) show

the major peaks observed in the individual PMMA and acetoacetanilide, with a small shift and

change in the intensity of the observed peaks . This confirms the presence of acetoacetanilide

crystals in PMMA matrix [9-10].

Vol.11, No.5 Incorporation of Acetoacetanilide Crystals 523

Table 1. Characteristic absorption peaks of PMMA, AA and the composite PMMA-AA

PMMA

Acetoacetanil ide

Composite PM-AA1 and PM-

AA2

Peak

position

cm-1

Bond Assignment

Peak

Position

cm-1

Bond Assignment

Peak

Position

cm-1

Bond Assignment

752

---CH

3300

--OH Stretching

3252

--OH Stretching

987

Bending (C-O)

2950

CH aliphatic str

2948

CH aliphatic str

1650

NH bending

1597

NH Bending

1200

(C-O)Stretching

1425

CH bending

1200

(C-O) Str

1723

Stretching C=O

1723

Str C=O

3.3 UV-Vis Spectral Analysis

The UV-Vis spectral data recorded in the wavelength range from 200-3000 nm for the pure and

PM-AA composites samples are shown in the Fig. 3.

050100 150 200 250 300 350 400450 500 550 600

[240 nm ]PM- AA2

[360 nm ]

[310 nm ]

PM-AA1

Absorbance [arb.u]

W avelength (nm )

Fig. 3 UV-Vis Absorption spectra of Pure A A an d composi te PM-AA Samples

The strong absorption peaks are evident from the UV absorption spectr a of the samples sho wn in

Fig. 3. A sharp absorption peak is exhibited by acetoacetanilide at 360 nm. The addition of

524 Sharada G. Prabhu and B.Manjunatha Pattabi Vol.11, No.5

acetoacetanilide in the host polymer environment causes the growth of crystals that is realized in

very strong absorption peaks in the PM-AA1 sam ple at 240 nm and a peak at 310 nm in the case

of the PM-AA2 sample. This suggests the blue shi ft in the absorption edge of acetoacetanilide in

the polymer matrix (PM-AA1 and PM-AA2) with respect to bulk ac etoacetanilide. The observed

blue shift indicates decrease in particle size.

Energy band of materials is related to absorption coefficient α by the Tauc relation

(αhν)=A(hν-Eg)n .

Where A is a constant, hν is the photon energy, Eg is the band gap and n is an index which

assumes values ½, 3/2, 2 or 3 d epending on the nature of electronic transition responsible fo r the

absorption. By taking the least index n=1/2 , (αhν)2 and hν in eV, the plot at room temperature

shows a linear behaviour of the absorption edge. The extrapolation of the li near part of the curve

on X axis gives the energy gap. The plot made for the samples (PM-AA1, PM-AA2) is shown in

the Fig. 4.

2.5 3.0 3.54.0 4.55.0 5.56.0 6.5

-50

100

150

200

250

300

350

400

3.25 eV3.75 eV4.95 eV

PM-AA2

PM-AA1

Bulk AA

(αhν)

Fig . 4 (αhν)2 and hν plot for the samples of PM-AA

The optical energy gap for the samples of PM-AA1 and PM-AA2 is increased to 3.75 eV and

4.95 eV respectively compared to bulk AA, which is 3.25 eV [11-12]. The absorption peaks and

the calculat ed energy gap from the absorption peaks (Fig. 3) and the energy gap from (αhν)2 and

hν plot for the bulk AA and composites of PM-AA1 and PM-AA2 are tabulated in the table. 2

shown below.

Vol.11, No.5 Incorporation of Acetoacetanilide Crystals 525

Table. 2. Absorption peaks and Energy Gap of acetoacetanilide and the composites of PM-

AA.

Samples

Absorption peaks

[λ Vs Absorbance]

Calculated energy

gap E

in eV

Energy gap in eV

[(αhν)2 Vs E

plot]

360 nm

3.45

3.25

PM-AA1

240 nm

5.175

4.95

PM-AA2

310 nm

3.75

3.4 SEM Analysis

The morphology of PM-AA blends has been studied using SEM. The SEM image of PM-AA

sample is shown in Figure 5.

(a)

(b)

Fig. 5 SEM micrograph images of PM-AA1 (a) and PM-AA2(b) composites

526 Sharada G. Prabhu and B.Manjunatha Pattabi Vol.11, No.5

The SEM images of PM-AA1 and PM-AA2 samples are shown in the Figure 5. The images

show pl at e type ( flak es) cr ystals with high crystal density. This is attributed to the agglomeration

of smaller crystals [13] due to high surface to volume ratio of the crystals.

3.5 SHG Meas urement

The second harmonic generation (SHG) measurement using the 1.06 μm pulsed radiation of a

Nd:YAG laser, as a fundamental wave has been carried out. It is demonstrated that PMMA and

acetoacetanilide are both non-linear and has second harmonic conversion efficiency. The blends

of PM-AA1 and PM-AA2 samples do not show an y second order conversion. That is the second

harmonic conversion efficiency is absolutely absent [14] for the composites of PM-AA.

4. CONCLUSIONS

The XRD an alysis reve a l s th at t he P MM A and acet oacetanil i de com po si te h as b een fo rmed . The

studies suggest the effectiveness of crystal size control, by temperature and evaporation

restriction and volume of the solutions used. Characteristic absorption bands from FTIR

spectrum of composites PM-AA are identified and assigned by comparison with the values found

for PMMA and acetoacetanilide individual materials. The presence of absorption peaks of

individual materials in the PM-AA composites confirms the incorporation of acetoacetanilide in

the PMMA host polymer. The change in the UV-visible spectrum is due to complex formation

which can be r efle cted in th e form of chan ge (d ecreas e in PM-AA s amples ) in the op tical ener gy

gap. Morphology of PM-AA shows crystalline domains uniformly shaped. The blend PM-AA

does not show any second harmonic conversion though acetoacetanilide has SHG property.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the financial support extended by Vishveshwaraya

Technological University, Belgaum, Karnataka, India by funding the project under VTU research

grant scheme. The author thanks Dr. Udaya Bhat and the research scholor Mr. Hebbar, Dept. of

Material s S ci ence an d M et al lu rg y, N ITK, S urat hkal, Karnataka, Indi a fo r p rov id in g XRD fa ci l ity

and Dr. Shyam Prasad, The Scientist, National Institute of Oceanography, Goa, India in helping

to make use of SEM facility. The author sincerely acknowledges Dr. Umesh, Dept of

Physics,NITK, Surathkal, for helping in carrying out laser facility.

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