Comprehensive Sequence Distribution Analysis of Butyl methacrylate-Acrylonitrile Copolymers by Two-dimensional NMR Spectroscopy

Abstract

ABSTRACT:The acrylonitrile-butyl methacrylate (A/B) copolymers were synthesized by solution polymerization utilizing 2,2 0 -azobisisobutyronitrile (AIBN) as free radical initiator. Reactivity ratios were assessed by KelenTudos and non-linear error in variable method and were found to be r A ¼ 0:37 AE 0:03, r B ¼ 1:44 AE 0:16 (KT) and r A ¼ 0:36, r B ¼ 1:40 (RREVM) respectively which confirmed that butyl methacrylate monomer is more reactive than acrylonitirile towards propagating chain during radical polymerization. 2D HSQC spectroscopy in conjugation with TOCSY afforded explicit information about compositional and configurational sequences. Methine and -methylene regions revealed compositional sensitivity up to pentad and tetrad level respectively with meso and racemic configurations. TOCSY demonstrated the coupling between the methine protons of A centered triad and pentad units with -methylene protons of various tetrads. Heteronuclear multiple-bond correlation (HMBC) spectroscopy has been employed to study carbon (carbonyl/nitrile)-proton coupling. The carbonyl and nitrile carbons expressed compositional sensitivity up to the triad level.

Polylactide/Poly(ω-hydroxytetradecanoic acid) Reactive Blending: A Green Renewable Approach to Improving Polylactide Properties

“…To obtain direct evidence that in situ synthesized PLA- b -PC14 interfacial compatibilizers were formed herein, two-dimensional (2D) NMR experiments ( 1 H– 13 C HSQC and HMBC) were performed. Both 1 H– 13 C HSQC and HMBC have proven to be useful in elucidating the microstructure of block polymers. , In HSQC and HMBC spectra, most sites throughout the interior of the polymers were detected as a single set of positional averaged resonances and are assigned according to literature values. − A few minor peaks were detected in both unreacted and reacted samples and assigned to the PLA hydroxyl end-group unit including 1 H peaks at 4.35 and 1.4 ppm and 13 C peaks at 66.75 and 16.82 ppm for the methine and methyl groups of PLA, respectively. From HMBC, signals due to the carboxyl end unit of PLA are also observed.…”

“…Both 1 H− 13 C HSQC and HMBC have proven to be useful in elucidating the microstructure of block polymers. 49,50 In HSQC and HMBC spectra, most sites throughout the interior of the polymers were detected as a single set of positional averaged resonances and are assigned according to literature values. 51−53 A few minor peaks were detected in both unreacted and reacted samples and assigned to the PLA hydroxyl end-group unit including 1 H peaks at 4.35 and 1.4 ppm and 13 C peaks at 66.75 and 16.82 ppm for the methine and methyl groups of PLA, respectively.…”