Complete Spectral Assignment of Poly(N-Vinylcarbazole-co-Methyl Acrylate)s by NMR Spectroscopy

Abstract

ABSTRACT:The copolymers of N-vinylcarbazole/methyl acrylate (V/M) of different compositions were prepared by solution polymerisation using 2,2'-Azobisisobutyronitrile (AIBN) as an initiator and their composition was determined from quantitative 13 C{ 1 H} NMR spectroscopy. Reactivity ratios for the comonomers were calculated using the Kelen-Tudos (KT) and non-linear error in variable methods (EVM). The complete spectral assignment of the overlapping 1 H and 13 C{ 1 H} spectra of the copolymers were done with the help of Distortionless Enhancement by Polarization Transfer (DEPT), two dimensional heteronuclear single quantum correlation (HSQC) and total correlated spectroscopy (TOCSY). The assignments of various compositional sequences were done in the carbon resonance signals of the methoxy region of M unit, the methine region of both V and M units and the methylene region of both V and M units.KEY WORDS Poly(N-vinylcarbazole-co-methyl acrylate)s / Two Dimensional Nuclear Magnetic Resonance (2D NMR) Spectroscopy / Microstructure / Poly(N-vinylcarbazole) (PVK) has been the subject of intensive investigation because it is one of the most sensitive photoconductive organic polymers. 1, 2 It has important applications in electrophotography, microlithography, electrochromic display devices, photoelectric devices, electroluminescent displays, and photothermoplastic imaging. 3 PVK is a stiff, brittle substance with poor mechanical and processing characteristics. Copolymerization with suitable monomers could soften the resulting product leading to better film properties and improve its mechanical properties. The copolymerization of N-vinylcarbazole with monomers like alkyl acrylates and alkyl methacrylates has been studied by several investigators. [4][5][6] The determination of microstructure in copolymers is of value in establishing structure-property relationship. 7 It is well known that NMR spectroscopy is probably the most effective method for characterizing the microstructure of polymers. [8][9][10] Crone and Natansohn 11 have reported the NMR analysis of microstructure of poly(methyl acrylate-co-N-vinylcarbazole). They have assigned the aliphatic and aromatic region in the proton spectra and aromatic region in the carbon spectra of the copolymers. However, some of the carbon and proton signals of the carbazole ring are erroneously assigned by them. They have reported the sequence distribution in the copolymers using C-1, 8a and H-1 resonance signals of the carbazole ring and the carbonyl carbon resonance signal of the M unit in the copolymer. However, they have not described the sequence distribution using the aliphatic region of the copolymer † To whom all correspondence should be addressed. spectra.Dais et al. 12 have reported the complete assignments of 1 H and 13 C spectra of PVK with the help of two-dimensional NMR techniques. In our earlier publication, 13 we reported the microstructure of Nvinylcarbazole/vinyl acetate copolymers using one and two-dimensional NMR spectroscopy. In continuation of our earlier w...

One- and two-dimensional NMR studies of methyl acrylate/vinyl acetate/N-vinyl carbazole terpolymers

“…The composition of terpolymers obtained from quantitative 13 C{ 1 H} NMR spectra were found to be in good agreement with those calculated from Alfrey-Goldfinger's equation [28]. The reactivity ratio of the comonomers calculated from Kelen-Tudos (KT) method are found as: r MA = 6.74 ± 1.03, r AM = 0.04 ± 0.01 for M/A copolymers [29], r AC = 0.26 ± 0.09, r CA = 5.86 ± 1.54 for A/C copolymers [22] and r MC = 0.65 ± 0.13, r CM = 0.07 ± 0.03 for M/C copolymers [21] while the reactivity ratio values observed from Error in Variable method (EVM) are: r MA = 6.72, r AM = 0.04 for M/A copolymers [29], r AC = 0.24, r CA = 5.41 for A/C copolymers [22] and r MC = 0.73, r CM = 0.08 for M/C copolymers [21].…”

“…1a. Various resonance signals were assigned by comparing 13 C{ 1 H} NMR spectra of terpolymers with N-vinyl carbazole/methyl acrylate [21], N-vinyl carbazole/vinyl acetate [22] and vinyl acetate/methyl acrylate [29] copolymers and their respective homopolymers [17,18,30,31]. Complex and overlapped methoxy, methine, methylene and carbonyl carbons were further resolved with the help of DEPT-135 NMR spectrum (Fig.…”

“…Complex and overlapped methoxy, methine, methylene and carbonyl carbons were further resolved with the help of DEPT-135 NMR spectrum (Fig. 1b) [21], vinyl acetate/methyl acrylate (A/M) [29] and N-vinyl carbazole/vinyl acetate (C/A) [22] copolymers using 2D NMR techniques. In continuation of our earlier work, in this manuscript, the detailed microstructural analysis of methyl acrylate/vinyl acetate/N-vinyl carbazole (M/A/C) terpolymers using 2D NMR (HSQC, TOCSY and HMBC) techniques was carried out.…”

“…This is due to the fact that 13 C{ 1 H} NMR chemical shifts are extremely sensitive to monomer and stereosequence effects. Various coworkers [18][19][20][21][22] have investigated the microstructure of N-vinyl carbazole based copolymers with different monomers. The stereosequence of different triads in various carbazole copolymers and terpolymers have earlier been reported using various 2D NMR techniques [23][24][25][26][27].…”

Comprehensive analysis of stereoregularity and sequence distribution in 2-N-carbazolylethyl acrylate and methyl methacrylate copolymers by 2D NMR spectroscopy and their thermal studies

“…It has been reported that copolymerization has a great influence on thermal properties of polymer [25,26].…”