M.L.S.U. Udaipur, Rajasthan, INDIA

American International Journal of Research in Science, Technology, Engineering & Mathematics Available online at http://www.iasir.net ISSN (Print): 2328-3491, ISSN (nline): 2328-3580, ISSN (CD-RM): 2328-3629 AIJRSTEM is a refereed, indexed, peer-reviewed, multidisciplinary and open access journal published by International Association of Scientific Innovation and Research (IASIR), USA (An Association Unifying the Sciences, Engineering, and Applied Research) Radical Homo and Copolymerization of Maleimide with Acrylic acid: effect of H-Bonding on Thermal Resistant Properties Jyoti Chaudhary 1, Swati Purohit 2, Suman Jinger 3 1,2,3 Department of Polymer Science M.L.S.U. Udaipur, Rajasthan, INDIA Abstract: The copolymers (C-NACPMI) with various proportions of N-[4-N -(4-nitrophenyl)amino carbonyl]phenyl)maleimide [NACPMI] and Acrylic acid [AA] were prepared by free radical polymerization in tetrahydrofuran (THF) using 2,2'-azo-bis-isobutyronitrile (AIBN) as an initiator at 70 ± 2 C.The structure of Monomer, Homopolymer and of Copolymers (C-NACPMI-1 to C-NACPMI-9) were characterized by FT - IR and 1 H- NMR spectroscopic methods. The nine copolymer samples were synthesized from different feed ratio of comonomers. The monomer reactivity ratio r NACPMI and r AA is determined by Finemann Ross method, r NACPMI = 0.1691 and r AA = 0.2545 respectively. The investigated homo and copolymers showed solubility in THF, DMF, Dioxane, acetone, chloroform, and ethyl acetate. Thermal behavior of homopolymer and copolymers were evaluated by TGA and DSC. The copolymers showed better thermal stability than Homopolymer due to secondary forces viz. Hydrogen bonding. The investigated copolymers degraded in one steps. The molecular weights were determined by GPC. The Antimicrobial activity of synthesized homopolymer and copolymer were screen and they show excellent Antimicrobial Activity. Keyword: Homo and Copolymerization, AIBN, Hydrogen bonding, TGA, GPC, Antimicrobial activity. I. Introduction Radical Homo and copolymerization behavior and thermal properties of Maleimides and its N-Substituted derivatives with Acrylates have been extensively studied by many workers. These polymers can be used as Heat Resistant materials [1]. High performance Polymers with well-defined architecture and controlled composition are of considerable interest for their academic and industrial uses [2]. Further Polymers with high glass transition temperature are attractive for industrial polymer science because of their strong economic rewards that may arise from their potential application [3]. Mainly two factors governs Tg of polymer are, Chain flexibility and chain interaction. Copolymerization is a best way to change both of them. Melting point or glass transition temperature depends on both monomers structure and their composition present in the polymer [4]. Hydrogen bonding is one of the important non covalent interactions in nature. The bonding energies for normal hydrogen bonds between 10-50 kj/mol. These stable and dynamic molecular complexes can be prepared by simple molecular self-assembly process using such hydrogen. If varieties of hydrogen bonding moieties are strategically introduced into synthetic polymeric and organic materials, new polymeric materials exhibiting a variety of functions can be obtained [5]. Introduction of Acrylic Acid [AA] into Polymer chain increases thermal stability of synthesized polymer due to Hydrogen bonding. Incorporation of Hydrogen bonding could also improve the T g of polymers to a great extent and this method has been studied in a varieties of copolymers [6]. Traditionally, infrared (IR) spectroscopy was the leading method for the identification of hydrogen bonds. The formation of an -H. hydrogen bond elongates and weakens the -H bond. The resulting red shift of the -H bond stretching frequency can be easily detected in the IR spectra, and its magnitude indicates the strength of the hydrogen bond. NMR chemical shift reflect the electronic structure in a molecule and therefore it identifying and characterizing hydrogen bond. In conventional hydrogen bonds, the bridging proton chemical shifts are moved downfield by 1-2 ppm [7]. By incorporating intermolecular H-bonding between [NACPMI] and [AA, the Tg was improved by 32. This article reports the solution radical copolymerization of [NACPMI] with Acrylic acid [AA].Effect of H- bond formation in between the C= group of maleic anhydride, and H group of acrylic acid has also been described and discussed. The synthesized copolymer was characterized by Infrared spectroscopy (IR), 1 H-NMR, elemental analysis, GPC, TGA and DSC. II. Materials and Method Azobisisobutyronitrile (AIBN), Acrylic acid (AA), THF, DMF was perched from Loba chemicals. All other reagents were used of analytical grade commercial products and used without any additional purification. 46

The monomer NACPMI was obtained by the reaction of maleic anhydride with 4-amino carboxylic acid according to a reported method [9]. The monomer N-[4-N -(4-nitrophenyl) amino carbonyl] phenyl) maleimide (NACPMI) was synthesized in three steps. In the first step N-(4-carboxy)phenyl maleimide ) (CPMI) was obtained by the condensation reaction of Maleic anhydride and 4-amino carboxylic acid followed by Cyclodehydration of N-(4- carboxy)phenyl maleimic acid (CPMA), using P 2 5 and conc. H 2 S 4 at 60. In second step N-[4-(chloro carbonyl) phenyl] maleimide (CCPMI) was synthesized. In third step N-[4-N -(4- nitrophenyl) amino carbonyl] phenyl) maleimide (NACPMI) was obtained [Scheme 1]. [Yield: 75%] Homopolymerization and Copolymerization of (NACPMI) were carried out in THF solvent, AIBN used as free radical initiator, [Scheme 2].For copolymerization equimolar amount of Monomer (NACPMI) and Acrylic Acid (AA) dissolved in THF, and then AIBN was added and refluxed for 24 hours. After a given time, polymers were precipitate out in methanol-water solution. Polymers were obtained as Yellow ppt and reprecipitated in Methanol. The process of precipitation is repeated two to three times.[yield :62 % ]. III. Result and Discussion A. Characterization Fourier transform infrared (FTIR) spectra was recorded on a FTIR Perkin-Elmer spectrophotometer model RX- I. The sample was prepared in KBr pellets, and the spectrum was obtained in the range 250-4000 cm 1. Nuclear Magnetic Resonance (NMR) spectra of newly synthesized monomer, homopolymer and copolymer have been scanned on BRUKER AVANCE II 400 MHz NMR Spectrometer. TMS uses as a reference. Structure of Monomer [NACPMI], Homopolymer [H-NACPMI] and Copolymer [C-CACPMI] were evaluated by FT-IR and 1 H-NMR spectroscopy. IR and 1 H-NMR spectra of monomer and polymer were shown in [Table 1] [Fig. 1, 2].The peak of (-CH=CH-) was disappear in homopolymer and copolymer showed that polymerization was carried out through this bond. The hydroxyl-stretching and the carbonyl-stretching band are sensitive to Hydrogen bonding. Hydrogen bonding brings about remarkable downward shift. Stronger the hydrogen bonding greater the absorption shift towards lower wave number than the normal value.intermolecular Hydrogen bonding give rise to broad band. Intermolecular hydrogen bonding is concentration dependent. Fig. 3 shows the hydrogen bonding between Carbonyl group in imide ring and Hydroxyl group in Acrylic acid. Hydrogen bonding increases with the amount of AA. Due to hydrogen bonding absorption frequency of C= and -H absorption occur at lower wave number. The concentration of AA was increases the peak of C= group at 1732 is NH 2 DMF, stirr, 4 h CH NH + room tempe. CH CH (CPMA) CH NH DMF, stirr, 4h N SCl 2, reflux N 60 4h CH (CPMA) CH (CPMI) CCl (CCPMI) 47

N + NH 2 THF, stirr, 4h N N 2 CCl (CCPMI) C NH N 2 (NACPMI) Scheme 1 Synthesis of Monomer (NACPMI) Scheme 2 Homo and Copolymerization of Monomer (NACPMI) 48

appear at lower concentration, as shown in [Fig.4], the associated carbonyl peak is observed at 1728, 1722, 1712 and H peak at 3375, 3368, 3364 and peak is broad. Table 1 FT-IR and 1 H-NMR spectral data of NACPMI, H-NACPMI and C-NACPMI Techniques NACPMI H-NACPMI C-NACPMI Characteristics FT-IR (CM - ) 3361 3361 3364 N-H Stretch of amide 1732 1717 1717 C= Sym. & Asym. stretch of imide 1682 - - C-C stretch of CH=CH 1650 1648 1665 C= Stretch of amide 1407 1394 1399 C-N-C stretch of N - Substituted maleimide 3032 3024 3028 C-H stretch of aromatic CH=CH 1505,1302 1504,1302 1504,1306 -N 2 Asym. And sym. Stretch 1 H-NMR (ppm) 6.92 6.6 6.6 Phenyl proton of rtho to N of imide 7.56 7.52 7.6 Phenyl proton of Meta to N of imide 7.8 8.0 7.9 Phenyl protons of rtho to amide 8.1 8.2 8.2 Phenyl protons of Meta to amide - - 10.81 -CH 6.6 - - (CH=CH) - 3.5 3.4 -[CH-CH] n- 9.92 9.75 10.1 -CNH - - 2.1 -CH2- B. Solubility Solubility of monomer, homopolymer and copolymer were tested in our laboratory by using solvents of varying solubility parameters and it was found that these were soluble in THF, DMF, DMS, Acetone, 1, 4 -Dioxane, Ethyl acetate, Chloroform. Whereas insoluble in Benzene, Toluene, n-hexane, Dichloromethane. The polymer showed solubility in polar solvents indicates the presence of polar group. C. Physical Properties ther characterization like Solubility, Viscosity, Density etc. were carried out in our laboratory. Density (ρ) depends on packing of Molecules in polymer chains. The density of homopolymers and Copolymer were determined at 30, by using Density bottle. Density of Homopolymer and Copolymer are given [Table 2]. The intrinsic viscosity of synthesized homopolymer and copolymers has been evaluated using Ubbelhode Suspended Level Viscometer at different concentrations ranging from 1.00 to 0.1% of copolymer in DMF at 30. Intrinsic viscosity [η] was calculated from plots of η red. against Concentration. By extrapolating linear plot to zero concentration, intercepts on the viscosity function axis give [η] value in plots. It was observed that copolymer having higher (Mn) showed higher value of [η] [Table 2]. Gel Permeation Chromatography (GPC) is the most common used technique to find out the molecular weight distribution in polymers varies from very low to very high molecular weight. Molecular weight of homopolymer and copolymers were analyzed on a Turbo matrix 40 Perkin Elmer, in THF solvent. Molecular weight and polydispersity index of Homo and Copolymer were determined by GPC using THF as a solvent. The number average molecular weight (M n ), weight average molecular weight (M w ) and Polydisperity (M w /M n ) are given in [Table 2]. 49

Fig. 1 FT-IR Spectra of (a) NACPMI (b) H-NACPMI (c) C-NACPMI Fig. 2 1 H-NMR spectra of (a) NACPMI (b) H-NACPMI (c) C-NACPMI 50

Fig 3 C=.. H interaction in C-NACPMI Table 2 Density,Intrinsic Viscosity, Molecular Weight of Homopolymer and Copolymer Polymer Code ρ(g/cm 3 ) ɳ(dl/g) M n M w PDI (Poly Dispersity Index) H-NACPMI 0.4601 0.1514 333.7 563.5 1.6890 C-NACPMI 0.8157 0.4559 762 436 1.7477 Fig. 4, FT-IR Spectra of C-NACPMI /AA Different ratios (d) 9:1 (e) 5:5 (f) 1:9 D. Copolymer Composition and Reactivity Ratios The copolymer compositions were determined by elemental analysis, [Table 3, 4]. The molar percentages of the comonomer units (m 1 and m 2 ) in poly(c-nacpmi-co-aa) were calculated with elemental analysis data (content of nitrogen). To determine the monomer reactivity ratios, the copolymerization of NACPMI with AA 51

using various monomer feed ratios by application of Fineman-Ross (FR) method [10]. The reactivity ratios r 1 and r 2 is the slope of FR plot and its intercept on y-axis, respectively. Alfrey and price derived a relationship to compute the reactivity ratios of various monomers. This method deals with the resonance stabilization (Q) and polarization characteristics (e) of a monomers and its reactivity behavior with reference to another monomer radical [11]. Table 3 Parameters for Fineman-Ross Methods to Determine Reactivity Ratios in Copolymer of C-NACPMI Code Mole Ratio W% of Mole Fraction of Finemann Ross Method Feed C-NACPMI C-NACPMI x 1:x 2 % N Feed X 1 Copolymer X1(1-2F1) /(1 - X1)F1 X 2 1 (F1-1)/(1-X1) 2 F1 C-NACPMI-1 1:9 8.23 66.05 0.1.195 0.348-0.050 C-NACPMI-2 2:8 8.58 68.86 0.2.252 0.492-0.185 C-NACPMI-3 3:7 9.32 74.79 0.3.315 0.504. -0.400 C-NACPMI-4 4:6 9.66 77.52 0.4.425 0.235-0.601 C-NACPMI-5 5:5 9.82 78.81 0.5.515-0.058-0.947 C-NACPMI-6 6:4 10.04 80.57 0.6.621-0.584-1.378 C-NACPMI-7 7:3 10.53 84.45 0.7.673-1.203-8.771 C-NACPMI-8 8:2 11.67 93.65 0.8.734-2.561-15.802 C-NACPMI-9 9:1 11.86 95.18 0.9.756-4.08-26.266 Table 4 Reactivity ratios of Monomers Polymer Code Reactivity Ratios(Finemann-Ross Method) Alfrey and Price Method r 1 r 2 Q E C-NACPMI 0.1691 0.2545 0.82 2.54 E. Effect of Solvent Initiator The percentage yield of homo and copolymers was determined in different solvents and initiator. It was observed that percentage yield in THF-AIBN system is high as compared to DMF, Acetone, Dioxane solvents. Viscosity of solvents are high life of free radicals and polymerization is high. Viscosity of THF is higher than the other solvents, so percentage yield is higher in THF. Viscosity of DMF is less than the other solvents, thus percentage yield was less [Table 5]. Table 5 Effect of Solvents and initiators on percentage yield of Polymer Solvents Solvent Viscosity Polymerization Time % Yield in AIBN initiators H-NACPMI F 1 % Yield in BP initiators H-NACPMI % Yield in AIBN initiators C-NACPMI % Yield in BP initiators C-NACPMI DMF 1.299 18 h 28.34 25.13 32.15 30.15 Acetone 1.359 18 h 29.08 28.78 33.42 34.15 Dioxane 1.416 18 h 34.45 32.65 46.72 45.12 THF 1.497 18 h 42.12 40.67 50.13 47.11 F. Thermal Behavior TGA analyses for polymers were conducted on a PerkinElmer Pyris1 TGA, Temperature Range of TGA: Room Temperature to 1000ºC, with a heating rate of 10 C/min in nitrogen. TGA measures the weight change in materials as a function of time and temperature. This measurement provides basic information about the thermal stability of a compound. The thermograms were interpreted and analyzed to obtain information about the % weight loss at different temperatures. Brief accounts of thermal behavior of these Homopolymer and Copolymers are given below in [Table 6, 7] [Fig. 5]. The thermal stability of copolymer was greater than homopolymer. If AA content in copolymer is less than 50% only a one step degradation process was detected, as the AA increased than this value two step degradation was observed due to interaction between Carbonyl group in imide ring and Hydroxyl group in AA. DSC analysis was performed on NETZSCH STA 449 F3Jupiter. The Value of Tg for homopolymer and copolymers with different Maleimide: AA obtained from DSC was summarized in [Table 8]. Addition of AA in a maleimide monomer results in a dramatic increase of Tg (Glass transition temperature) as the concentration of AA increases. The higher Tg value of copolymers were due to negative entropy of mixing which is associated with the strong hydrogen bonding due to presence of AA in higher concentration(>50%)]. Table 6 Percentage weight loss of H-NACPMI, C-NACPMI at various temperature range from the TGA. Polymer Code Weight loss (%) 200 300 400 500 600 700 H-NACPMI 38.821 75.871 78.67 85.77 87.87 92.23 C-NACPMI 42.012 65.345 73.453 80.254 82.451 89.234 Table 7 Thermal Behavior of H-NACPMI, C-NACPMI. 52

Polymer Code T i T max. T f Residue at 700 H-NACPMI 150 200 210 7.77 % 380 500 620 C-NACPMI 120 180 195 10.766 % 360 470 610 Table 8, Effect of MI/AA ratios on T g S.No. MI / AA T g / from DSC 1 10:0 57.6 2 9:1 114 3 5:5 128 4 1:9 146 Fig. 5 TGA Diagram of (a) H-NACPMI (b) C-NACPMI (9:1) (c) C-NACPMI (5:5) (d) C-NACPMI (1:9) G. Microbial Activity Antibacterial and Antifungal activity of monomer (NACPMI), homopolymer (H-NACPMI) and Copolymer (C- NACPMI) against bacteria s and Fungus were carried out. Synthesized Monomer and Polymers showed good Antibacterial activity against bacteria (Esherichia aerogenes, Staphylocous aureus ) and antifungal activity against fungi ( Aspergillus nizer, Alternaria solani).the antimicrobial activity of Homopolymer and Copolymer were due to presence of heteroatoms in polymers.[table 9,10] [Fig. 6, 7]. Table 9 Antibacterial activity of NACPMI, H-NACPMI and C-NACPMI against bacteria Esherichia aerogenes, Staphylococus aureus Code 500(μg/ml) Concentration of compound taken Zone of Inhibition For E. aerogenes Zone of inhibition for S. aureus (mm) (mm) NACPMI 7 7.2 H-NACPMI 8 7 C-NACPMI 11 13 Table 10 Antifungal activity of NACPMI, H-NACPMI, C-NACPMI against fungus Aspergillus nizer, Alternaria solani Code 100(μg/ml) Concentration of compound taken Zone of Inhibition For A. nizer Zone of Inhibition For A. solani (mm) (mm) NACPMI 7 9 H-NACPMI 6 8 C-NACPMI 18 20 53

American International Journal of Research in Science, Technology, Engineering & Mathematics Available online at http://www.iasir.net ISSN (Print): 2328-3491, ISSN (nline): 2328-3580, ISSN (CD-RM): 2328-3629 AIJRSTEM is a refereed, indexed, peer-reviewed, multidisciplinary and open access journal published by International Association of Scientific Innovation and Research (IASIR), USA (An Association Unifying the Sciences, Engineering, and Applied Research) Fig. 6 Antibacterial activity of polymer Fig. 7 Antifungal activity of polymer IV. Conclusion The Radical homopolymerization and copolymerization of NACPMI was carried out in THF solvents using AIBN as a initiator. The structure of synthesized monomer, homopolymer and copolymer were confirmed by FT-IR and 1 H-NMR spectral analysis. The presence of hydrogen bonding in copolymers were evaluated by FT- IR. Homopolymer and copolymer were soluble in polar solvent indicating polar behavior of polymers. The molecular weight of homopolymer and copolymer were determined by GPC. The synthesized homopolymer and copolymer was degrade in two steps and shows excellent thermal stability up to 700. The copolymers derived from NACPMI and AA with different ratios show that the reactivity ratio of NACPMI, r 1 is less than r 2. This result shows higher reactivity of AA as compared to NACPMI. Copolymer showed better thermal stability and higher Tg value than homopolymer due to presences of secondary forces viz hydrogen bonding. All synthesized homo and copolymer showed good antimicrobial activity, could be ideal candidates for amtimicrobial coating application. Acknowledgements We are gratefully acknowledge Head, Department of Polymer Science, M. L. S. University Udaipur for providing lab facility and Botany Department and Biotechnology Department for Antifungal activity and antibacterial activity, also SICART, Vallabh Vidyanagar, Gujarat,SAIF Chandigarh and Chennai for sample analysis. References [1] Y. Ren,Z. Zhu and J. Huang, Radical Copolymerization of Maleimide with Ethy α Ethylacrylate and α Ethylacrylic Acid via RAFT, J polymer scienec : Part A : Polymer Chemistry,vol. 42,2003, pp. 3828-3835. [2]. Akitoshi,Y. Shinya and M. Akikazu, The effect of side chain length and hydrogen bonding on the viscoelastic property of Isobutene/maleimide Copolymers, Macromolecular Chemistry and Physics,vol. 210, 2009, pp.1210-1217. [3] K. Backfolk, Determination of the glass transition temperature of latex films : comparison of various methods, Polymer Testing, vol. 26 (8), 2007,pp. 1031-1040. [4] A. Mbulu, Preparation of polystyrene with Higher Tg based on triple hydrogen bond interaction, Materials Science, 2008,vol. 23. [5]. Ahmet,K. Ayse, The effect of H-Bonding on radical copolymerization of Maleic Anhydride with N-tert-Butylacrylamide and its Characterization, International journal of Polymer science, vol. 2013, 2013,pp. 1-9. [6] Q.H. Zhou, L.Ming,P. Yang,G. Yi, Effect of Hydrogen bonds on Structures and Glass transition temperatures of Maleimide- Isobutene Alternating Copolymers:Molecular Dynamics Simulation Study, Macromolecular,vol. 22,2013,pp. 107-114. [7] B.Wang, J.F.Hinton, P.Putlay, C.H.. Hydrogen bonding between N-Methyl maleimide and Dimethyl Sulfoxide : A Combined NMR and Ab Initio Study, J. Phys.Cem.,vol. 107, 2003,pp. 4683-4687. [8] B.L. Hiram, S.N. Paliwal, Free Radical Initiated Polymerization of N-[4-N -{(4-chlorophenyl) amino-carbonyl} phenyl]maleimide and Characterization of Homopolymer and Copolymers with MMA Journal of Macromolecular Science, Part A: Pure and Applied Chemistry, vol.46, 2009, pp. 713 721. [9] M. Finemann,S.D. Ross, Journal of applied polymer science,vol. 5, 1950,pp. 259. [10] T. Alfrey,C.C. Price, Journal of applied polymer science,vol. 2, 1947,pp. 101. 54