Synthesis and Characterization of Poly(aniline-co-D-cycloserine)

K. Masilamani, G. Selvanathan*

Department of Chemistry, A.V.C College (Autonomous), Mannampandal, Mayiladuthurai -609305, Tamil Nadu,

*Corresponding Author E-mail: jeeselvanathan@yahoo.com

ABSTRACT:

Poly(aniline-co-D-cycloserine) was prepared by electrochemical and chemical oxidative polymerization. The copolymer thin films of aniline-cycloserine were synthesized by using cyclic voltammetric technique in an aqueous sulfuric acid on the Glassy carbon electrode. The copolymer formation, the electrochemical behavior and the structure were examined. The analogous copolymers were prepared via a chemical oxidative polymerization in 1M HCl in the presence of Potassium persulfate as an oxidant. The structure of the copolymer was studied by IR, 1H NMR and X-ray powder diffraction (XRD) and the surface morphology was studied by SEM.

KEY WORDS: D-cycloserine, oxidative polymerization, electrochemical method, Glassy carbon electrode.

INTRODUCTION:

Electrically conducting polymers are the subject of continuous research and development of potential applications in optical and electronic devices, electromagnetic shielding, energy storage systems, corrosion protection, sensors and microelectronic devices. Polyaniline (PANI) has been in the forefront of the global search for commercially available conducting polymers because of its unique proton dopability, low cost, ease of synthesis, excellent redox recyclability, and variable electrical conductivity, thermal and chemical stability. Therefore, PANI can be used as an electrode material in the fabrication of secondary batteries in microelectronics and in electrochromic display material [1-4]. However, there are limitations in the applicability of PANI as it is usually obtained chemically as an insoluble powder and electrochemically as thin brittle film. Similarly, PANI has a rigid and planar backbone providing good conductivity but the same feature makes it insoluble in common organic solvents and incompatible with common polymers. This necessitates modification of the PANI structure to achieve better processability.

Considerable progress has been made in the last few years in the modification of the PANI chain leading to better processibility by the post treatment of parent PANI base, the synthesis of polymer blends and composites, soluble substituted anilines and copolymers of aniline with substituted anilines. Among these methods copolymerization is considered to be an important method to improve the properties of homopolymers.

D-cycloserine or D-4-amino-3-isoxazolidinone (Fig-1) is an antibiotic produced by Streptomyces garyphalus and Streptomyces orchidaceus[5].

D-Cycloserine is effective against Mycobacterium tuberculosis. It is classified as a second line drug, if one or more first line drugs cannot be used [6-7]

Fig-1 Structure of D-cycloserine

Copolymerization is a simple way of preparation of new polymers, and it greatly increases the scope of tailor-making materials with specifically desired properties[8]. The copolymerization potential of two different monomers plays an important role in the properties of a copolymer as well as the deposition potential of two different kinds of metallic ion for the electrochemical preparation of a metallic alloy[9]. Changing the monomer concentration ratio[1] one can readily control the copolymerization potential of two monomers. Among the various techniques available for the electrochemical synthesis of conducting polymers, the cyclic voltammetry has been used for the fast production of the good quality polymer films[10].

In the present investigation, the cyclic voltammetry method was used for the electrochemical copolymerization of aniline and D-cycloserine aiming at correlating the growth behavior of copolymer film deposition with experimental conditions.

For comparison the copolymers were synthesized by chemical oxidative polymerization and characterized.

2. EXPERIMENTAL:

2.1 Materials

Pharmaceutical preparation of D-cycloserine was purchased and recrystallized from ethanol. 5mM stock solution of the substrate was prepared in 1:1 aqueous ethanol. Aniline was distilled under reduced pressure; Potassium persulfate (Merck), sulfuric acid and methanol (Merck) were used as received. All solutions were prepared using bidistilled water.

2.2 Synthesis of aniline and D-cycloserine copolymer

2.2.1 Electrochemical polymerisation

Electrochemical polymerization of aniline and cycloserine was carried out using a software controlled electrochemical analyzer Model CHI 620D (Make: CH Instruments, Inc., USA) provided with a three electrode single compartment cell assembly. A Glassy carbon (GC) of surface area of 0.0314 cm², a platinum wire and Ag/AgCl were used as working, counter and reference electrodes respectively. The homo and copolymerization was carried out in the aqueous solution of 1M H₂SO₄. The homo polymer of aniline and copolymers of aniline with D-cycloserine films were deposited using cyclic voltammetry for 30 cycles. The solution was purged well with nitrogen gas and all the experiments were carried out in nitrogen gas atmosphere.

2.2.2 Chemical copolymerization

Copolymer of poly(aniline-co-D-cycloserine) was chemically synthesized using potassium persulphate as initiator in an aqueous acidic medium at 0-4⁰C in a similar manner to that previously described[11-13]. A typical procedure adopted for the preparation of copolymer is as follows.

Monomers, aniline (0.4M) and D-cycloserine (0.1M) were dissolved in 50 ml of 1M HCl and cooled to 0-4⁰C. The oxidant potassium persulphate (0.05M) was dissolved separately in 50ml of 1M HCl and cooled to 0-4⁰C. Then the oxidant solution was added drop wise to the monomer solution for an hour with constant stirring in nitrogen atmosphere at 0-4⁰C. After the addition of oxidant, the solution was stirred for 7 hours for the completion of the reaction. The greenish black precipitate was obtained and the reaction mixture was kept overnight. Then the copolymer precipitate was filtered, washed with distilled water until the filtrate became colourless and finally with methanol and dried in an air oven at 60⁰C for 8 hours.

3. RESULT AND DISCUSSION:

3.1 Copolymerization of Aniline and D-Cycloserine

The cyclic voltammogram of 0.04M aniline in 0.1M H₂SO₄on a stationary Glassy carbon electrode with a potential range from 1.2 to -1.0V at a scan rate of 100mV/sec. is shown in Fig.2.

The voltammogram shows an anodic peak at 0.32V and a cathodic peak at 0.39V in the first cycle. The peak current steadily increased with increase in number of cycles. This is due to autocatalytic polymerization, which causes quick polyaniline (PANI) film growth as the electropolymerisation proceeds. After completion of 30 cycle, a green-color polymer film on the working electrode was observed.

The monomers of 0.4M aniline and 0.1M cycloserine on GCE were polymerized in 0.1M H₂SO₄ medium by repeated potential cycling between 1.4 and -1.0 V.

The cyclic voltammogram shows two anodic peaks at 1.0V and 0.46V (Fig-3). The anodic peak current was increased in successive cycles. A peak similar to the oxidation peak of aniline at 0.46V appeared in the forward scan and in the reverse scan peak PANI peak disappeared. At the same time a new oxidation peak appeared at 1.0V. This behaviour suggests the copolymerization of both aniline and D-cycloserine (aniline-co-D-cycloserine). The bluish-green-color film seen on the working electrode indicates the formation of new type of polymer.

3.2 Effect of Scan Rate

The polymer film thus obtained was washed with ultrapure water and subjected to the scan rate variation studies between the potential range -1.0 and +1.4V in 0.1M H₂SO₄ medium. The typical cyclic voltammogram is shown in Fig-4. A linear relationship was observed between the peak current and scan rate indicating a well-adhered electroactive polymer film on the coated electrode.

Fig-7 SEM images of the poly(aniline-co-D-cycloserine

3.3 FT-IR spectral analysis of poly(aniline-co-D-cycloserine)

The IR band position of poly(aniline-co-D-cycloserine) is shown in Fig-5

The band at 3448cm⁻¹ is attributed to the NH₂ stretching of aromatic primary amines, since both monomer units contain –NH₂ groups. The band at 3743cm⁻¹ is attributed to the C-H stretching. The band at 2922cm⁻¹ is attributed to the C-H anti-symmetric and symmetric stretching. A peak at 2372 cm⁻¹ is attributed to the N-H stretching.

The two bands around 1689and 1654cm^-1 is attributed to the C=O stretching vibrations of the phenyl ring and NH₂ deformation. The prominent peaks around 1550cm⁻¹and 1464cm^-1is indicating the N-H deformation of secondary amines. The occurrence of this band clearly shows that these copolymers are composed of NH units. The copolymer showed the band around 1244cm⁻¹ is assigned as the C-N stretching, for the C-N stretching in aromatic amines are in the range 1280–1180cm⁻¹. A prominent band at 1018cm⁻¹is indicative of the carbon ring in cyclic compound.

A band at 669cm⁻¹ is attributed to the mono substituted benzene ring stretching.

The above results in the FT-IR spectrum of copolymer demonstrated that an electrochemical copolymerization of aniline and cycloserine took place most probably at the given conditions. The FT-IR spectrum of the copolymer indicates that there are –NH₂group, –NH group and cyclic carbon ring in the copolymer film. Hence, the monomer aniline and cycloserine units are present in the copolymer.

3.3. ¹H NMR spectral analysis of Poly(aniline-co-D-cycloserine)

The ¹H NMR spectra of Poly(aniline-co-D-cycloserine) shown in Fig. 6.

The main signals are discussed here. The signals at 6.99, 7.12, 7.25 and 7.38ppm can be assigned as aromatic protons. The signals at 0.85, 1.15, 1.23, 2.09, 2.22, 2.33, 2.38, 2.26ppm can be assigned as alicyclic protons. The signals at the regions 3.8ppm can be attributed to the NH₂ protons. The IR and ¹H NMR spectral data’s support that the green polymer deposited on the working electrode is a copolymer.

3.4 Morphology of poly(aniline-co-D-cycloserine)

Scanning electron micrographs (SEM) of the copolymer provide a clear morphology of the copolymer. The SEM images of the poly (aniline-co-D-cycloserine) was prepared from aniline (0.4M) and D-cycloserine (0.1M) is shown in Fig-7

The SEM images show a nano structure with homogeneous spongy and fibrous structure. The SEM morphology obtained indicates the presence of polymer overgrowth leading to agglomeration.

3.5 XRD of Poly(aniline-co-D-cycloserine)

The X-ray diffraction analysis is also a powerful tool to determine the structure and crystallization of polymer matrices. The phase in which the polymer chains are parallel and ordered in close packed array is the crystallites region, while the phase where the chains are not ordered and do not have parallel alignment is the amorphous region. This ordered arrangement of polymer chains in the crystalline phase may be of different types depending on the nature of the polymer and can be detected from X-ray diffraction. Fig-8 shows X-ray diffraction pattern of Poly(aniline-co-D-cycloserine)

The XRD patterns of the poly(aniline-co-D-cycloserine) seems to be comprised with one broad peak situated at approximately 12.97^o and do not show sharp peaks characteristic of crystalline materials. Careful analysis of X-ray diffraction of poly(aniline-co-D-cycloserine) suggests that it has amorphous nature.

4. CONCLUSION:

Poly(aniline-co-D-cycloserine) was synthesized under cyclic voltammetric conditions in pH 1 sulfuric acid medium on the surface of the working Glassy carbon electrode. The analogous copolymers were prepared via a chemical oxidative polymerization in 1M HCl in the presence of potassium persulfate as an oxidant.
The structure of the copolymer was systematically studied by IR, ¹H NMR, X-ray powder diffraction (XRD) and the surface morphology was studied using SEM analysis. The participation of NH group in the chemical synthesis of new poly(aniline-co-D-cycloserine) has been proved by IR results. The X-ray diffraction of poly(aniline-co-D-cycloserine) suggests, it has amorphous nature. The SEM studies show the presence of nano particles

5. REFERENCES:

1. Manisankar.P, Vedhi.C, Selvanathan.G and Somasundaram.R.M, Electrochemical and Electrochromic Behavior of Novel Poly(aniline-co-4,4’-diaminodiphenyl Sulfone), Chem. Mat.,17 (2005) 1722-1727

2. Gupta.R.K., Singh.R.A, Preparation and characterization of polymer composites of polyaniline with poly(vinyl chloride) and polystyrene, Journal of Non-Crystalline solids, 351 (2005) 2022-2028.

3. Yiting Xu, Lizong Dai, Jiangfeng Chen, Jean-Yves Galm Huihuang Wu Synthesis and characterization of aniline and aniline-o-sulfonic acid copolymers, European Polymer Journal, 43 (2007) 2072-2079

4. Siyu Ye, Do. N.T, Dao.Le H. Ashok K. Vijh, Electrochemical preparation of conducting copolymers: poly(aniline-co-N-butylaniline), Synthetic Metals, 99 (1997) 65-72.

5. Murali Pendela, Sanja Dragovic, Lien Bockx, Jos Hoogmartens, Ann Van Schepdael, Erwin Adams, Development of a liquid chromatographic method for the determination of related substances and assay of d-cycloserine, Journal of Pharmaceutical and Biomedical Analysis,47 (2008) 807–811

6. Mae Newton, Nicolaas C. Gey van Pittius, The complex architecture of mycobacterial promoters J.Tuberculosis 93 (2013) 60-74

7. Suhail Ahmad, Eiman Mokaddas, Recent advances in the diagnosis and treatment of multidrug-resistant tuberculosis, Respiratory Medicine 103 (2009) 1777-1790

8. De Zayas-Blanco.F, Garcıa-Falcon.M.S, Simal andara.J, Determination of sulfamethazine in milk by solid phase extraction and liquid chromato- graphic separation with ultraviolet detection, Food Control, 15 (2004) 375–378

9. Bagheri. A; Nateghi, M.R ; Massoumi A, Synthetic Metals, 97 (1998) 85.

10. Shaolin.M, Synthetic Metals, 143 (2004) 259.

11. Borkar.A.D, Gupta.M.C, Umare.S.S., Poly. Plast. Technol. Eng., 40(2) (2001) 225.

12. Borkar A.D, Umare S.S, International Journal of Chemical Sciences, 8(2) (2010) 1110.

13. Borkar A.D, Umare S.S, Heda P.B. , Mat. Res.Innova., 15(2) (2011) 135.

Received on 31.01.2014 Modified on 15.02.2014

Asian J. Research Chem. 7(2): February 2014; Page 209-213