CHARACTERIZATION OF INTRAMOLECULAR MICROSTRUCTURE OF STYRENE METHYL-METHACRYLATE COPOLYMERS - NEW H-1-NMR ASSIGNMENTS SUPPORTED BY 2D-NOESY NMR

The methoxy H-1 NMR signals in the sigma 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 sigma, yields consistent results (sigma = 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.