Comprehensive Assignments of 1H and 13C NMR Signals for the Vinylidene Chloride-Butyl Acrylate Copolymers Using 2D NMR Spectroscopy

Abstract

ABSTRACT:Vinylidene chloride-butyl acrylate copolymers were prepared by photopolymerization at room temperature. The molecular weight of these copolymers have been determined using Gel Permeation Chromatography and the copolymer composition estimated using Schoneger technique. 2D NMR techniques such as 1 H-13 C heteronuclear single quantum correlation (HSQC) was used for the compositional and configurational assignments of 1 H and 13 C{ 1 H} NMR spectra for various resonating signals. 2D 1 H homonuclcar double quantum filter-correlated spectroscopy (DQF-COSY) is used to get better insight for the copolymer structure.KEY WORDS Photopolymerization / Gel Permeation Chromatography / Composition / Heteronuclear Single Quantum Correlation / Correlated Spectroscopy / Vinylidene Chloride / Butyl Acetylate / Copolymer/ Two dimensional homonuclear and heteronuclear NMR spectroscopy have been used extensively for the structure elucidation of polymers. The microstructure of homopolymers 1 such as poly(methacrylonitrile), 2 poly-(vinyl chloride), 3 polyisobutylene,4 poly(tert-butyl acrylate)5 and poly(cyclohexyl acrylate) 6 have reports by 2D NMR spectroscopy. 2D NMR has also been used for the characterization of the copolymers. 7 ,sIn our earlier publications on vinylidene chloridemethyl acrylate copolymers,9 we have determined their microstructure and reported the detailed assignment of the 13 C{ 1 H} NMR signals. In this the methine and methylene signals were assigned upto triad and diad levels respectively on the 1 H NMR using heteronuclear single quantum correlation (HSQC) experiments. Further splittings on the HSQC for these resonating regions were attempted in the vinylidene chloride-ethyl acrylate10 where the methine and methylene signals were assigned upto pen tad and tetrad levels, respectively. But 2D-COSY spectrum was not discussed in detail. In the continuation of our work, we report the 2D studies of commercially important 11 vinylidene chloride-butyl acrylate (V-B) copolymer by using one dimensional (1H and 13 C) and two dimensional NMR spectroscopy. The 2D-COSY spectrum shows all the I, 2 bond geminal couplings feasible for the methylene protons along with the 1, 3 bond coupling of the methine with the methylene protons. EXPERIMENT ALVinylidene chloride (Fluka) and butyl acrylate were freed from inhibitor by distilling under reduced pressure prior to use. The copolymers are prepared by photopolymerization 12 • 13 using uranyl nitrate as photosensitizer. 14 The molecular weights of the copolymers were determined by gel permeation chromatography (GPC) using polystyrene as narrow standard (Waters, 410). Tetrahydrofuran was used as solvent.t To whom all correspondence should be addressed.The compos1t10n was determined using Schoneger technique. 15 · 16 The 1 D NMR spectra and the 2D HSQC spectra of the copolymers were recorded on a JEOL 300 MHz spectrometer, whereas 2D DQF-COSY spectra was recorded on the Bruker-DPX 300 MHz spectrometer. Experimental details are mentioned in our earlier publication. 9 RESULTS AND...