Experimental Section Polymer 13C NMR spectra were measured with an ARX-300 spectrometer at 140 °C in bromobenzene-d5 with 40–60 mg/mL and 14k scans with 5 mm OD tubes. Acquisition conditions were: 30° flip angle; 1.82 sec acquisition time, 2 sec relaxation delay. Broad-band proton decoupling was achieved with a WALTZ16 sequence. The degree of isotacticity was determined via the integration of the corresponding [mmmm]-pentade (21.85 ppm)15 against the region of 19.5–22.5 ppm.
