Application of {deuterium}carbon-13 INEPT NMR to the study of polymer reactivity

Strictly Alternating Sequences When Copolymerizing Racemic and Chiral Acetylene Monomers with an Organo-Rhodium Catalyst

“…Nevertheless, SPAs have proven valuable as advanced polymer materials, e.g., as a chiral stationary phase for optical resolution columns of racemic small molecules. − ,− Detailed structural information on HSPAs is needed to rationalize the intrinsic functional properties. It is still not known whether the copolymers possess alternating, random, and/or block sequences, although knowledge of their microtacticity has been considered crucial for various types of vinyl or styrene polymers. − Using various pieces of spectroscopic evidence, we reveal strictly alternating monomer sequences in poly­(( rac )-2-methyl-1-butyl propiolate) (R = CH 2 CH­(CH 3 )­CH 2 CH 3 ) composed of R 1 and S 1 monomer units in a ratio of 1:1. This structural information can be used to propose a prevailing polymerization mechanism.…”

Sequence distribution determination of deuterated polybutadiene by {deuterium}carbon-13 INEPT triple resonance NMR experiments

“…Deuterated polymers such as butadiene have been used in studies on the structure and properties of polymer blends via small-angle neutron scattering (SANS).1•2 Previous efforts to characterize this polymer using its olefinic carbon resonance pattern were unsuccessful, and a determination based on the aliphatic carbon resonances appeared to yield a high value for the trans content of the polymer.3 These difficulties were encountered because scalar deuteriumcarbon coupling produced a spectrum with a complex group of overlapping multiplets which could not be interpreted. In previous papers3"" 5 The spectra in c and d were acquired with a 0.2-s relaxation delay, a 20-ms polarization transfer delay, a 5-ms refocusing delay for (c) and a 14-ms refocusing delay for (d), a 0.599-s acquisition time, a 16 502-Hz spectral window, and 20 480 transients. The Figures lb and 2b.…”