Characterization of intramolecular microstructure of styrene-methyl methacrylate copolymers: new proton NMR assignments supported by 2D-NOESY NMR

Abstract

The methoxy 1H NMR signals in the 8 2.10-3.70 region for statistical styrene-methyl methacrylate copolymers have been reassigned for several methyl methacrylate centered triad/pentad resonances. Former literature assignments for statistical copolymers were inconsistent with experimental results. New peak assignments are completely based on pentad sequence distributions. Supporting evidence for these reassignments is 2-fold: First, comparison of theoretically calculated and experimentally observed peak areas, and the use of various independent procedures for the determination of the coisotacticity parameter u, yields consistent results (u = 0.44). Second, 2D-NOESY (Nuclear Overhauser effect spectroscopy) NMR experiments were carried out for alternating as well as for statistical copolymers. The results supported the proposed reassignments.