Stereochemical Assignments of the Nuclear Magnetic Resonance Spectra of Isobornyl Acrylate/Methacrylonitrile Copolymers Deepika Khandelwal, 1 Sunita Hooda, 2 A. S. Brar, 3 Ravi Shankar 1 1 Department of Chemistry, Indian Institute of Technology Delhi, New Delhi 110016, India 2 Department of Chemistry, Acharya Narendra Dev College, Govindpuri, Kalkaji, New Delhi 110019, India 3 Guru Nanak Dev University, Amritsar, Punjab, India Received 4 August 2011; accepted 27 November 2011 DOI 10.1002/app.36545 Published online in Wiley Online Library (wileyonlinelibrary.com). ABSTRACT: Isobornyl acrylate (B)/methacrylonitrile (N) copolymers with different compositions were synthesized by the free-radical bulk polymerization with azobisisobutyr- onitrile as the initiator under a nitrogen atmosphere at 70  C. The copolymer compositions were calculated from quantitative 13 C( 1 H)NMR spectra. The reactivity ratios of the comonomers in the B/N copolymers determined from the linear Kelen–Tudos method and nonlinear error-in-vari- able method were r B ¼ 0.66 6 0.11 and r N ¼ 1.54 6 0.22 and r B ¼ 0.74 and r N ¼ 1.65, respectively. The complete spectral assignments of the 1 H-NMR and 13 C( 1 H)-NMR spectra were carried out with the help of distortionless enhancement by polarization transfer, two-dimensional (2D) heteronuclear single quantum coherence, and 2D total cor- relation spectroscopy. The nitrile carbon of the N unit and the methine and OCH carbons of the B unit were assigned to triad compositional sequences, whereas the b-methylene carbons of the B and N units were assigned to the tetrad compositional and configurational sequences. The a-methyl carbon of the N unit was also assigned to the triad level of configurational and compositional sequences. Similarly, the nitrile and quaternary carbon resonances with the methine, methylene, and methyl protons were studied in detail with 2D heteronuclear multiple-bond correlation spectra. V C 2012 Wiley Periodicals, Inc. J Appl Polym Sci 000: 000–000, 2012 Key words: microstructure; NMR; polymer synthesis and characterization INTRODUCTION Copolymers of isobornyl acrylate (B) are of great in- terest in many industrial applications, for example, cosmetics, 1 coatings, 2 bioapplications, 3 drug-delivery systems, 4 and construction material, 5 because of their high glass-transition temperature 6 and hard- ness. 7,8 The macroscopic properties of bulk polymers are influenced fundamentally by their chain micro- structure, which can be investigated by NMR spec- troscopy. 9–11 Two-dimensional (2D) NMR spectros- copy has become a very important and valuable technique for determining polymer structure. 2D heteronuclear single quantum coherence (HSQC) and total correlation spectroscopy (TOCSY) provide a correlation between 1 H and 13 C nuclei that are one bond apart in the polymeric chain. 9,12,13 Various researchers have reported controlled radical poly- merization of copolymers of B by atom transfer radi- cal polymerization 14–16 and nitroxide-mediated poly- merization. 17 The thermal behavior and microstructural studies of polymethacrylonitrile (PMAN) and its copolymers were reported ear- lier. 18,19 Brar and coworkers 20–22 reported the reactiv- ity ratios and microstructure of methacrylonitrile (N) copolymers with other vinyl monomers. To the best of our knowledge, the stereochemical assignments of complex and overlapped NMR spectra of the B/N copolymers have not yet been reported. In this study, we examined the reactivity ratios of the comonomers in the B/N copolymers using the Kelen– Tudos (KT) 23 method and the nonlinear error-in- variable 24 method (EVM). The compositional and con- figurational sequence determination of the B/N copolymers was carried out by one-dimensional (1D) and 2D NMR spectroscopy. The 13 C( 1 H)-NMR and 1 H-NMR spectra of the copolymers were quite com- plex and were interpreted with the help of distortion- less enhancement by polarization transfer (DEPT) and 2D HSQC–NMR spectroscopy. The 2D TOCSY spec- trum was used to explain the 1 H– 1 H correlation in the B/N copolymers, whereas 2D heteronuclear multiple- bond correlation (HMBC) spectroscopy was used to determine the long-range interactions between differ- ent groups present in the copolymer. Correspondence to: A. S. Brar (asbrar@chemistry.iitd.ernet.in). Contract grant sponsor: University Grant Commission, New Delhi, India (to D.K.). Journal of Applied Polymer Science, Vol. 000, 000–000 (2012) V C 2012 Wiley Periodicals, Inc.