Title: Characterization of 4-vinylpyridine-styrene copolymer by NMR spectroscopy
Abstract: 13 C{ 1 H }-NMR spectra. The observed triads concentration as determined from 13 C{ 1 H} NMR spectra are in good agreement with those calculated from statistical model using terminal model reactiv ity ratio s. The complete spectral assignment of these copolymers has been done with the help of Di stortionless Enhancement by Polari za tion Transfer (DEPT) and two dimensional heteronuclear single qu antum coherence (HSQC) spectra. The various type of 1 H- 1 H couplings in copolymer are ass igned with the help of 2D-Total correlated spectroscopy (TOCSY). It is well established that differences in monomer se quence distribution within synthetic copolymers can result in difference in physical properties of copoly mers. Consequently, knowledge of the microstructure is important to understand the macroscopic charac teristics of copolymers 1 • NMR spectroscopy is being frequently used for the study of sequence determina tion in many homopolymers 2 · 4 and copolymers 5 • 6 . DEPT is used extensively for the analysis of over lapped carbon resonances in 13 C-NMR spectra 7 • 8 . Co polymers of vinylpyridine with styrene and butadiene are used as tyre cord adhesives for bonding reinforc ing fibres to a rubber matrix 9 • The interesting proper ties of vinylpyridine polymers are due to the presence of weakly basic nitrogen atom which makes possible a varieties of reactions e.g. reaction with acids, qua temization and complexation of metals. Poly (vinyl pyridine) has been employed as electron beam resists, an attractive feature being the outstanding plasma etch resistance due to the aromatic nature of polymers. Yilmaz et al. 10 have reported the reactivity ratios of V/S copolymers at low and high conversion. Petit et al. 11 have assigned the various triad sequences in quaternary carbon of V- and S-unit. In continuation of the earlier work, in this paper we report the copolym erization mechanism of V /S copolymers prepared by free radical bulk polymerization. The copolymer compositions were determined from 1 H NMR spectroscopy. The reactivity ratios were calculated from KT and EVM methods. The triad sequence distribu tion were obtained from NMR spectra and statistical model using terminal model reactivity ratios . The mi crostructure parameters, e.g., conditional probabili ties, number- average sequence lengths and block character of V /S copolymers were calculated from triad/ diad concentration obtained from 13 C{ 1 H} NMR spectra. The highly complex and overlapped 1 H
Publication Year: 2001
Publication Date: 2001-05-01
Language: en
Type: article
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