Characterization of 4-vinylpyridine-styrene copolymer by NMR spectroscopy

Abstract

4-Vinylpyridine-styrene (V/S) copolymers of different compositions have been prepared by free radical bulk polymerization. The copolymer composition has been calculated from ¹H NMR spectra. The co-monomer reactivity ratios of V/S copolymer have been calculated from Kelen-Tudos (KT) and non-linear error in variables methods (EVM). The reactivity ratios

obtained from KT and EVM are r_V = 0.85, r_S = 0.67 and r_V =0.80± 0.20, r_S = 0.66 ± 0.05 respectively. The copolymerization parameters such as conditional probabilities, number - average sequence lengths and block character in the copolymers have been calculated from ¹³C{¹H}-NMR spectra. The observed triads concentration as determined from ¹³C{¹H}-

NMR spectra are in good agreement with those calculated from statistical model using terminal model reactivity ratios. The complete spectral assignment of these copolymers has been done with the help of Distortionless Enhancement by Polarization Transfer (DEPT) and two dimensional heteronuclear single quantum coherence (HSQC) spectra. The various type of ¹H-¹H couplings in copolymer are assigned with the help of 2D-Total correlated spectroscopy (TOCSY).