Complete NMR assignment of a sulfonated aromatic block copolymer via heteronuclear single-quantum correlation, heteronuclear multiple-bond correlation and heteronuclear single-quantum correlation total correlation spectroscopy

Abstract

A sulfonated aromatic block copolymer (SABC), consisting of hydrophobic and hydrophilic blocks, was analyzed by heteronuclear single-quantum correlation (HSQC), heteronuclear multiple-bond correlation (HMBC) and HSQC total correlation spectroscopy (HSQC–TOCSY). Because of its complicated chemical structure with five different phenylene rings, 12 types of 1H signals and 24 types of 13C signals were observed in a narrow chemical shift range (7.0–8.0 p.p.m. for 1H and 118–162 p.p.m. for 13C). To improve the 1H signal separation, the temperature conditions for the 1H nuclear magnetic resonance (NMR) experiments were optimized. Moreover, 1H and 13C NMR signal assignments for the hydrophobic blocks were performed using HSQC and HMBC, with reference to the assignments of a model oligomer. For the hydrophilic blocks, furthermore, HSQC–TOCSY techniques were applied. As a result of these studies, complete 1H and 13C NMR signal assignments were made for the SABC. The ion-exchange capacity (IEC) and the copolymerization composition were calculated using the 1H NMR assignments for the SABC, and the IEC value obtained in this way was consistent with that obtained via titration. A sulfonated aromatic block copolymer (SABC), consisting of hydrophobic and hydrophilic blocks, was analyzed by 2D NMR techniques of HSQC, HMBC and HSQC–TOCSY. Because of its complicated chemical structure with five different phenylene rings, 12 types of 1H signals and 24 types of 13C signals were observed in a narrow chemical shift range (7.0–8.0 p.p.m. for 1H and 118–162 p.p.m. for 13C). As a result of these studies, complete 1H and 13C NMR signal assignment of SABC was performed.