Studies on Reactivity Ratio and Thermal Studies of Copolymers of N-Substituted Maleimide with Vinyl Pyridine [VP]/2-Hydroxy ethylmethacrylate [OHEMA]

 

Jyoti Chaudhary¹, Swati Purohit¹*, Radha Chaudhary²

¹Department of Polymer Science, M.L. Sukhadia University, Udaipur (Rajasthan) India

²Department of Chemistry, G.I.T.S., Udaipur (Rajasthan) India

*Corresponding Author E-mail: purohit.swati3@gmail.com

The copolymers (C-NACPMI) with various proportions of N-[4-N’-(4-nitrophenyl) aminocarbonyl] phenyl) maleimide [NACPMI] with Vinyl Pyridine [VP] and 2-hydroxy ethylmethacrylate (OHEMA) were prepared by free radical polymerization. The structure of synthesized copolymers was characterized by FT - IR and ¹H- NMR spectroscopic methods. The nine copolymer samples were synthesized from different feed ratio of comonomers. The monomer reactivity ratio r NACPMI_, r VP and r OHEMA are determined by Finemann Ross method. Copolymers showed solubility in polar solvent. Thermal behavior of copolymers was evaluated by TGA and DSC. The investigated copolymers degrade in one steps. The molecular weight was determined by GPC.

 

 

 

INTRODUCTION:

High performance Polymers with well-defined architecture and controlled composition are of considerable interest for their academic and industrial uses¹_.The past three decades have witnessed a significative increase in the use of polyimides including properties like high tensile strength and modulus, excellent heat, chemical and corrosion resistance. Polyimides are belongs to a class of high performance polymers².  Reactivity ratios are the most important parameters for composition equation of copolymers and they offer information about the reactivity of monomer pairs. However, the copolymer composition is important in evaluating its own utility.

 

The copolymer composition and its distribution are dependent on their reactivity ratios, which can be evaluated either by employing linear and nonlinear methods or by using other copolymer composition equations ³ Copolymerization is one of the important techniques for systematic changes in the properties of the polymers. Copolymers with reactive or functional monomers are steadily gaining importance. Many copolymers with reactive functional groups are now being synthesized, tested and used not only for their macromolecular properties, but also for the properties of functional groups. These functional groups provide an approach to a subsequent modification of the polymer for the specific end applications ⁴. Herein, we discuss on the synthesis and characterization of copolymers containing acrylate-maleimide units as electron rich and electron acceptors units with the results of their thermal and antimicrobial properties. It was observed that such copolymers have better thermal stability than the polymers of vinyl monomers. The studies of physical and spectral properties have been carried out in order to characterize the copolymer sample.

EXPERIMENTAL:

Materials and Method:

All chemicals were used as received. 4-Amino carboxylic acid, Maleic anhydride, Vinyl Pyridine (VP), 2-Hydroxy ethylmethacrylate (OHEMA), THF, AIBN were purchased from Sigma Aldrich. Copolymer NACPMI-co-VP and NACPMI-co-OHEMA was synthesized according to reported method⁵ [Scheme 1]. Structure was confirmed by FT-IR and ¹H-NMR.

 

RESULT AND DISCUSSIONS:

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 used as a reference. FT-IR and ¹H-NMR data are summarized in Table 1 and 2.

 

 

Scheme 1 Synthesis of Copolymers

 

Molecular weight:

The molecular weight of the synthesized copolymers was measure by Gel permeation chromatography (GPC) analysis. GPC is a reliable and fast technique to determine the polydispersity index (PDI) and molar mass averages of polymers. The number average and weight average molecular weights (Mn, Mw) and polydispersity index of epoxy resin were summarizes in [Table 3].

 

Table 1: FT-IR data of Copolymers

Characteristics	NACPMI-co-VP	NACPMI-co-OHEMA
N-H stretch of amide	3367	3365
C=O sym. and asym. stretch of imide	1710	1722
C=O stretch of amide	1648	1664
C-N-C stretch of  N-substituted maleimide	1407	1398
-NO2asym. and sym. Stretch	1515,1306	1504,1306
C=C and C=N stretch in pyridine ring	1598,1503	-
C-O-C stretch of ester	-	1178
C-O stretch in pri. Alcohol	-	1077
C-H bending CH=CH	Disappeared*	Disappeared*
C-C stretch of CH=CH	Disappeared*	Disappeared*

 

 

 

 

Table 2: ¹H-NMR data of Copolymers

Characteristics	NACPMI-co-VP	NACPMI-co-OHEMA
Phenyl proton of ortho to N of imide	6.5	6.4
Phenyl proton of meta to N of imide	7.7	7.6
Phenyl protons of ortho to amide	7.9	8.0
Phenyl protons of meta to amide	8.3	8.2
Proton of -CONH	10.1	10.5
Methylidene proton (-CH2-)	2.5	2.3
Methylene proton (CH=CH)	Disappeared*	Disappeared*
-[CH-CH]n-	3.5	3.6

*Peaks are disappeared due to polymerization

 

 

Copolymer Composition and Reactivity Ratios:

The molar percentages of the co monomer units (m₁ and m₂) in NACPMI-co-VP and NACPMI-co-OHEMA were calculated with elemental analysis data (content of nitrogen). To determine the monomer reactivity ratios, the copolymerization of NACPMI with VP and OHEMA using various monomers feed ratios by application of Fine man-Ross (FR) method⁶. The reactivity ratios r₁ and r₂ 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 radical⁷. [Table 4] The value of r₁ is less than r₂ in both polymers indicates reactivity of other comonomer is higher than the maleimide monomer, maleimide monomers is less reactive. Values of r₁ and r₂ indicate distribution of monomer in polymer chain is random distribution of polymer.  Reactivity of Vinyl Pyridine (VP) is high in comparison to 2-Hydroxy ethylmethylacrylate (2-OHEMA), It shows that in copolymerization with maleimide moiety reactivity of vinyl pyridine is high. The value of Q and e by Alfrey-Price equation are summarized in Table 4. Large values of e indicate the electron acceptor nature of maleimide monomer.

 

Table 3 Molecular Weight and PDI of copolymers

Polymers	Mn	Mw	PDI(Mw/Mn)
NACPMI-co-VP	472.8	891.2	1.8344
NACPMI-co-OHEMA	643.2	1106.8	1.7207

 

 

Table 4 Reactivity ratios of Monomers

Polymer Code	Reactivity Ratios(Finemann-Ross Method)		Alfrey and Price Method
	r1	r2	Q	e
NACPMI-co-VP	0.1946	0.2894	0.95	2.87
NACPMI-co-OHEMA	0.1681	0.3197	1.10	3.28

TGA Analysis

 

Data derived from TG curves are furnished in [Table 5] Thermogram of copolymers is given in Figure 1, depicts one step decomposition reaction. Examination of TGA data reveals that the copolymers start degradation around 100 ⁰C and remain 47.43% around 700 ⁰C.  Thermal stability of NACPMI-co-VP is higher than NACPMI-co-OHEMA, because Here thermal stability depends on electron substituent effect and size of group present on vinyl monomer.

 

 

Table 5 TGA Analysis of copolymers

Polymer code	100 0C	200 0C	300  0C	400 0C	500 0C	600 0C
NACPMI-co-VP	11.94	29.209	31.946	47.676	55.337	65.818
NACPMI-co-OHEMA	2.63	18.7	47.12	59.01	67.88	83.88

 

Fig. 1 TGA Analysis curve

 

CONCLUSION:

The Radical copolymerization of NACPMI was carried out in THF solvents using AIBN as a initiator. The structure of synthesized copolymers was confirmed by FT-IR and ¹H-NMR spectral analysis. 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 ⁰C. The copolymers derived from NACPMI with VP and OHEMA with different ratios show that the reactivity ratio of NACPMI, r₁ is less than r₂. This result shows higher reactivity of VP and OHEMA as compared to NACPMI. Copolymer showed better thermal stability.

 

ACKNOWLEDGEMENTS:

We are gratefully acknowledging Head, Department of Polymer Science M. L. S. University Udaipur for providing lab facility also SICART, Vallabh Vidyanagar Gujarat, SAIF Chandigarh and Chennai for sample analysis.

 

REFERENCES:

1.        Akitoshi O, Shinya Y and Akikazu M. The effect of side chain length and hydrogen bonding on the viscoelastic property of Isobutene/maleimide Copolymers. Macromolecular Chemistry and Physics.210; 2009: 1210-1217.

2.        Mathur P, Joshi RK, Rai DK, Jha B and Mobin SM. One pot synthesis of maleimide and hydanotin by Fe(CO)(5) Catalyzed (2+2+1) co-cyclization of acetylene, iscocynate and CO. Dalton Trans. 41; 2012: 5045.

3.        Hemalatha P, Veeraiah MK, Prasanna SK, Madegowda NM, Manju NM. Reactivity Ratios of N-Vinylpyrrolidone - Acrylic Acid Copolymer. American Journal of Polymer Science. 4(1); 2014: 16-23.

4.        Hiran BL, Boriwal R, Bapana S, Paliwal SN. Synthesis and Characterization of Polymers of Substituted Maleimide Derivatives, Journal of the University of Chemical Technology and Metallurgy. 15(2); 2010: 127-132.

5.        Jyoti Chaudhary, Swati Purohit and Radha Chaudhary. Copolymers of MA/EA/BA with N-Substituted Maleimide: Synthesis, Characterization and Effect on the Thermal Properties. International Journal of Engineering Sciences and Research Technology, 5(8); 2016: 314-320.

6.        Finemann M, Ross SD. Journal of applied polymer science. 5; 1950: 259.

7.        Alfrey T, Price CC. Journal of applied polymer science. 2; 1947: 101.

 

 

 

Received on 01.04.2017         Modified on 18.04.2017

Accepted on 28.04.2017         © AJRC All right reserved