Propylene incorporation in 1-butene copolymers by carbon-13 nuclear magnetic resonance spectrometry

Monomer Sequence Distributions in Propylene−1-Butene Random Copolymers

“…Figure 4 shows the extended carbon-13 NMR peaks of the methyl carbon in the propylene unit. According to the previous assignments [1][2][3][4][5][6][7][8][9]11 and this expanded experimental result, it can be seen that methyl carbons have lower comonomeric sequence sensitivity than configurational sequence sensitivity. For example, differences among the triad comonomeric sequence distributions, PPP, PPB, and BPB, are less than 0.15 ppm; however, differences among the triad configurational sequence distributions, PPP (mm), PPP (mr) and PPP (rr), are over 0.80 ppm, that is to say, all the comonomeric sequences are compressed only in the region of the triad configurational sequence PPP (mm).…”

“…Figure 1 shows the carbon-13 NMR spectrum of a selected propylene copolymer with 8.17 mol % 1-butene comonomer, most peaks of which can been identified and assigned in terms of the previous assignments. [1][2][3][4][5][6][7][8][9] However, a few peaks in the experiment remain unclear. It was natural to link these new peaks to the configurational structure of propylene sequence, since the samples used in the study contained small amounts of 1-butene, and from comparison of the chemical shifts of these peaks with those of a propylene homopolymer 11 it was concluded that such a link was reasonable.…”

“…[1][2][3][4][5][6][7][8][9] The studies of Randall, Cheng, and Aoki are considered the most significant in this field: 3,6-8 they determined the chemical shift assignments of triad and tetrad sequences from chemical shift calculations using empirical rules and comparison of the spectra of copolymers with different compositions. 3,4 In addition, the pentad and hexad sequence assignments were proposed from quantitative analysis of the spectrum by a reaction probability model.…”

“…Propylene−1-butene copolymers, unlike ethylene−propylene copolymers and ethylene−1-butene copolymers, have received relatively less attention in carbon-13 NMR studies, even though over 20 years ago the carbon-13 NMR technique was utilized to characterize their molecular microstructure and to determine the monomer sequence distributions. − The studies of Randall, Cheng, and Aoki are considered the most significant in this field: 3,6-8 they determined the chemical shift assignments of triad and tetrad sequences from chemical shift calculations using empirical rules and comparison of the spectra of copolymers with different compositions. , In addition, the pentad and hexad sequence assignments were proposed from quantitative analysis of the spectrum by a reaction probability model . Aoki et al advanced the study in this field: 7,8 use of the powerful 2D-INADEQUATE technique determined the carbon-13 NMR chemical shift assignments in propylene−1-butene copolymers and confirmed the validity of previous assignments of triad and tetrad sequences .…”

NMR Analysis of Stereo Regular Copolymers

“…The enchainment of the monomer units Was essentially isotactic and head-tail. Resonances observed for the homopo1ymers, assignments made previously by Fish and Dannenberg [78], the Grant-Paul relationships and variations in resonance intensity with copolymer composition were used to make assignments for the resonances of methine, methylene and methyl carbon atoms. Triad and some tetrad sequence distribution measured from the spectra were consistent with Bernou1lian distributions over the entire range of copolymer compositions examined.…”