NMR and thermal studies of N-acryloylcarbazole/methacrylonitrile copolymers

Abstract

Copolymers with different compositions of N-acryloylcarbazole (A) and methacrylonitrile (M) are reported here. Composition of the copolymer has been determined by ¹H NMR spectrum. The comonomer reactivity ratios, determined by both Kelen-Tudos (KT) and non-linear error-in-variables (EVM) methods are <i>r</i>_A<i>= </i>1.27 ± 0.13, <i>r</i>_M<i>= </i>0.69 ± 0.06, and <i>r</i>_A<i>=</i>

1.30, <i>r</i>_M = 0.69, respectively. Complete spectral assignments of the ¹Hand ¹³C{¹H} NMR spectra of the copolymers is done by Distortionless Enhancement by Polarization Transfer (DEPT) and Heteronuclear Single Quantum Coherence (HSQC) techniques. The methylene carbon signals of both (A and M) units have been found to be sequence sensitive. The signals

obtained are broad, pertaining to the restricted rotation of bulky carbazole group and the quadrupolar effect of nitrogen present in carbazole moiety. The thermal stability and glass transition temperatures (<i>T</i>_g)<i> </i>of the copolymers are dependant on polymer composition and characteristic of rotational rigidity of the polymer chain. Variation in the values of <i>T_g </i>with the copolymer composition has been found to be in good agreement with theoretical values obtained from Johnston and Barton equations.