Complete Spectral Assignments and Microstructures of Photopolymerized Acrylonitrile/Methacrylic Acid Copolymers by NMR Spectroscopy

Dutta

1998

Polym J

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ABSTRACT:The stereochemical structures of poly(pentyl acrylate) (PPA) prepared by solution polymerization is studied by the combination of one and two dimensional NMR spectroscopy. The OCH2, methine, methylene, and the carbonyl carbon resonances are assigned to triad, tetrad and pentad sequences respectively. The polymerization mechanism was studied using the carbonyl and OCH2 resonances. It was found that homopolymerization followed Bernoullian statistics. The various configurational assignments in the aliphatic region were done with the help of inverse HETCOR, inverse HETCOR-TOCSY, homonuclear DQFCOSY experiments.KEY WORDS Poly(pentyl acrylate) / ID and 2D Nuclear Magnetic Resonance Spectroscopy / Stereochemical / Microstructure / Homo and copolyacrylates are of great interest in many industrial applications because of their wide range of physical and chemical properties that can be covered by an appropriate choice of side groups and copolymer system. Poly(pentyl acrylate) (PPA) is used as a viscosity index improver because of large pendant group. The physical and chemical properties of these polymers are greatly influenced by the microstructure, which involves the monomer distribution in the polymer chain and stereochemical arrangement of various groups. Thus the determination of configurational sequence distribution appears to be important. 1 The knowledge of the microstructure is essential to study the polymerization mechanism. 2 NMR spectroscopy is probably the most efficient technique for characterization of the stereochemical structure of polymers. 3 · 4 Many workers 5 -9 have reported the stereochemical structure of polyacrylates by conventional one dimensional NMR spectroscopy. The contribution of two dimensional nuclear magnetic resonance spectroscopy (2D NMR) to the study of homopolymer microstructure has been universally recognized. 10 Recently, the microstructure of the polyacrylates were studied by the application of inverse HETCOR (heteronuclear correlation) and DQFCOSY NMR spectroscopies. 11 -13 In this manuscript, we report the microstructure of PPA and the polymerization mechanism. The various carbon resonances are assigned to triad, tetrad and pentad configurational sequences with the help of two dimensional homonuclear (DQFCOSY) and heteronuclear (inverse HETCOR) correlation NMR spectroscopy. 2D 1 H-13 C heteronuclear correlation was used to assign the proton NMR spectra of the homopolymers. The geminal and the vicinal couplings possible in the various configurational sequences in the homopolymer were studied by 2D 1 H-1 H DQFCOSY NMR spectroscopy.t To whom all correspondence should be addressed. 304 EXPERIMENT ALPentyl acrylate was synthesized by esterification of pentanol with acrylic acid using the Dean and Stark apparatus. Benzene was used as azeotropic agent to remove the water from the reaction mixture. The monomer was vacuum distilled and stored below 5°C. The PP A was prepared by solution polymerization using benzoyl peroxide as intiator in DMF at 65°C. The homopolymer was precip...

“…The details of the Lorentzian shaped curve fitting have been described in our earlier publication. 16 All regressions converged to x 2 < 1.…”

Section: Experiments Almentioning

confidence: 88%

Stereochemical Characterization of Poly(pentyl acrylate) by One and Two Dimensional NMR Spectroscopy

Dutta

1998

Polym J

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“…The various onedimensional (1D) ( 1 H, 13 C{ 1 H}, DEPT) and 2D (HSQC, TOCSY) NMR spectra were recorded in CDCl 3 on a Bruker DPX-300 NMR spectrometer using different standard pulse sequences as described in our previous research. 24,30 The molecular weight averages were determined by gel permeation chromatography (GPC) using polystyrene as a narrow standard, as given in Table 1. The molecular weight determination was carried out on a Waters GPC instrument attached with a refractive-index detector using a Styragel-HR4 column.…”

Section: Methodsmentioning

confidence: 99%

“…Poly(isobutylene-co-methylstyrene) has been characterized by 1 H and 13 C NMR by Ashbaugh et al 18 Wohlrab and Kuckling 19 and Virtanen and Tenhu 20 have researched the copolymers of N-isopropylacrylamide with 2-vinylpyrrolidone and glycidyl methacrylate, respectively. Many researchers have reported the sequence distribution of methyl acrylate with vinylidene chloride, 21 vinyl acetate, 22,23 and acrylonitrile 24 copolymers. Brar and Kumar 25,26 have reported the sequence distribution of N-vinyl-2-pyrrolidone with acrylonitrile and glycidyl methacrylate.…”

Section: Introductionmentioning

confidence: 99%

One‐ and two‐dimensional NMR characterization of N‐vinyl‐2‐pyrrolidone/methyl acrylate copolymers

J. Polym. Sci. A Polym. Chem.

Kumar

2002

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N-vinyl-2-pyrrolidone/methyl acrylate (V/M) copolymers were prepared by free-radical bulk polymerization using benzoyl peroxide as an initiator. The copolymer composition of these copolymers was calculated from 1 H NMR spectra. The radical reactivity ratios for N-vinyl-2-pyrrolidone (V) and methyl acrylate (M) were r V ϭ 0.09, r M ϭ 0.44. These reactivity ratios for the copolymerization of V and M were determined using the Kelen-Tudos and nonlinear least-squares error-in-variable methods. The 13 C{ 1 H} and 1 H NMR spectra of these copolymers overlapped and were complex. The complete spectral assignment of the 13 C and 1 H NMR spectra were done with distortionless enhancement by polarization transfer and two dimensional 13 C-1 H heteronuclear single quantum correlation spectroscopic experiments. The two-dimensional 1 H-1 H homonuclear total correlation spectroscopic NMR spectrum showed the various bond interactions, thus inferring the possible structure of the copolymers.

“…All the 1D ( 1 H, 13 C{ 1 H} and DEPT) and 2D (HSQC and TOCSY (18 ms)) NMR spectra of the copolymers were recorded in CDCl 3 on Bruker 300 MHz DPX spectrometer at 25 • C using the concentration of 10-15% (w/v) and the standard pulse sequences as reported in our earlier papers. 16,17 The copolymer composition was determined experimentally by quantitative 13 C{ 1 H} NMR spectroscopy using inverse gated decoupling pulse program where relaxation delay was kept 10 s. The molecular weight averages were determined by GPC (Gel Permeation Chromatography) using the polystyrene as narrow standards.…”

Section: Spectramentioning

confidence: 99%

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

Kaur

2002

Polym J

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...