Comprehensive analysis of stereoregularity and sequence distribution in 2-N-carbazolylethyl acrylate and methyl methacrylate copolymers by 2D NMR spectroscopy and their thermal studies

A series of 2-N-carbazolylethyl acrylate (C) and methyl methacrylate (M) copolymers with varying compositions were prepared in toluene at 60 °C using AIBN as an initiator. The molar outfeed ratio (FC) for various compositions was determined from 1H NMR spectra. Reactivity ratios calculated using Kelen-Tudos (KT) and non-linear error in variable (RREVM) methods were found to be rC=0.43±0.8 and rM=2.78±0.52. Molecular weight distribution was determined by gel permeation chromatography (GPC). The methine carbon of C unit showed splitting up to the pentad level in 13C{1H} NMR spectra and was found to be sensitive to the variation in C/M copolymer compositions. The backbone methylene and carbonyl carbons of both M and C unit along with α-methyl carbon of the M unit showed both compositional and configurational sensitivity. Distortionless enhancement by polarization transfer (DEPT) helped in differentiating the methylene carbon signals from the methine and methyl carbon resonances. 2D heteronuclear single quantum coherence (HSQC) and 2D total correlation spectroscopy (TOCSY) were used in tandem to deduce all spectral assignments. 2D heteronuclear multiple bond coherence (HMBC) played an important role in studying the stereoregularity of the carbonyl carbon. The trend in variation of glass transition temperature (Tg) of various C/M copolymer compositions was also studied.