Absolute tacticity assignments of poly(vinyl chloride) via the two-dimensional NMR spin-lock RELAY experiment

Crowther, Molly W.; Szeverenyi, Nikolaus M.; Levy, George C.

doi:10.1021/ma00159a009

Cited by 33 publications

(4 citation statements)

References 8 publications

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“…19 RESULTS AND DISCUSSION Figure 1 shows the 400 MHz 1 H NMR spectrum of PMMA prepared in toluene at -78°C by t-C 4 H 9 MgBr. It is evident from the a-CH 3 and CH 2 signals that the PMMA is highly isotactic as reported in the previous literature, 17 • 18 though signals due to the monomeric units at and near the a-and w-ends also appear in this region. The peak assignments were made with the aid of 2D NMR spectra as described below.…”

supporting

confidence: 79%

Two-Dimensional NMR Spectra of Isotactic Poly(methyl methacrylate) Prepared with t-C4H9MgBr and Detailed Examination of Tacticity

Hatäda

Ute

Tanaka

et al. 1987

Polym J

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ABSTRACT:Structures of the chain ends of the low molecular weight and highly isotactic PMMA prepared by t-C4 H 9 MgBr in toluene were investigated extensively using 2D NMR technique. The 1 H and 13 C NMR signals of ix-CH 3 and CH2 groups in the first two and the last two monomeric units of the chain were assigned unequivocally, and four types of end-structures, viz. mm and rm at ix-end and mm and mr at w-end were identified. The configurations at the ix-and wends were less isotactic than those of in-chain monomeric sequences, and the m/r ratios at the ix-and w-ends were 10/1 and 6/4, respectively. Exact tacticity of PMMA was determined on the basis of the assignment, which revealed that isotacticities of the PMMAs prepared with t-C4 H9MgBr in toluene at -78°C were independent of molecular weight. Chemical shifts of configuration-sensitive peaks for fractionated dimers and trimers of MMA were found to be very similar to those of the corresponding structures in the polymer ends.KEY WORDS Isotactic Poly(methyl methacrylate) / Tacticity / 1-Butylmagnesium Bromide / 1 H and 13 C NMR / 2D NMR / COSY Spectrum / 2D J-Resolved Spectrum / Dimer and Trimer of Methyl Methacrylate / ix-End and w-End / End Group Analysis /

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supporting

confidence: 79%

Two-Dimensional NMR Spectra of Isotactic Poly(methyl methacrylate) Prepared with t-C4H9MgBr and Detailed Examination of Tacticity

Hatäda

Ute

Tanaka

et al. 1987

Polym J

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“…The weight average molecular weight and polydispersity index (M w and M w /M n , respectively) were calculated on the basis of polystyrene standards. 13 C NMR spectra obtained in a mixed solvent of benzene-d 6 and o-dichlorobenzene from the area of each split peak of the methine carbon [32]. The tacticity of the PVC thus determined was: mm = 16%, mr = 47%, rr = 37%, respectively, which are close to those obtained with the conventional radical polymerization reported (mm = 12%, mr = 49%, rr = 39%) [32].…”

Section: Resultssupporting

confidence: 73%

Another example of carborane based trianionic ligand: Syntheses and catalytic activities of cyclohexylamino tailed ortho-carboranyl zirconium and titanium dicarbollides

Zhu

Sia

Kooli

et al. 2005

Journal of Organometallic Chemistry

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“…ID Spectrum. In Figure 1 is shown the expanded view of methylene carbon resonance region of the 13C NMR spectrum of PVCW (whole polymer) with the assignments given by Crowther et al 2 The observed relative areas of methylene tetrad peaks were obtained from this spectrum. On the other hand, the relative peak areas were calculated by Bernoullian propagation statistics (selection between m and r).…”

Section: Resultsmentioning

confidence: 96%

Carbon-13 NMR chemical shift assignments of poly(vinyl chloride) based on the 2D-INADEQUATE spectrum

Nakayama¹,

Aoki²,

Hayashi³

1994

Macromolecules

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Two-dimensional (2D) heteronuclear lH-13C, homonuclear lH, and spin-lock relay NMR experiments have been used to provide 13C NMR chemical shift assignments of stereosequences in poly(viny1 chloride). However, relative areas of methylene tetrad peaks based on the assignments given by these 2D NMR experiments do not agree with the relative areas predicted by Bernoullian propagation statietica. Since the methods of the 2D experiments are correct, this is a puzzle. In thie study, tetrad and pentad assignments are proposed on the basis of the carbon-carbon connectivities revealed by the 2D-INADEQUATE (twodimensional incredible natural abundance double quantum transfer experiment) spectrum. The tetrad assignments given by 2D-INADEQUATE experiments show that there are two mmr peaks and that one of them overlaps the mrm peak. These assignments differ from the previous assignments and resolve the contradication in relative peak areas. The relative areas of methylene peaks based on the assignments from the 2D-INADEQUATE spectrum agree with those predicted by Bernoullian propagation statistics. Introductionl3C NMR is the most powerful method to analyze the sequence structures in vinyl polymers. Complicated split peaks arising from pentad or hexad sequences are usually observed in the high-resolution NMR spectra. Recently, two-dimensional (2D) NMR experiments have been developed and used as a reliable method of making assignments in high-resolution spectra.In the field of 13C NMR spectral analysis of poly(viny1 chloride) (PVC), 2D heteronuclear lH-l3C, homonuclear 'H, and spin-lock relay NMR experiments have been used to provide 13C NMR chemical shift assignments of stereosequences in PVC.1*2 Crowther et aL2 have demonstrated (from the spin-lock relay experiment) that the mrm and mmr tetrads are reversed from previous assignment in a similar solvent.314However, the authors found that the relative areas of methylene tetrad peaks based on the assignments given by these 2D experiments1P2 do not agree with the relative areas predicted by a Bernoullian propagation model (selection between m and r). The sample used for this

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Absolute tacticity assignments of poly(vinyl chloride) via the two-dimensional NMR spin-lock RELAY experiment

Cited by 33 publications

References 8 publications

Two-Dimensional NMR Spectra of Isotactic Poly(methyl methacrylate) Prepared with t-C4H9MgBr and Detailed Examination of Tacticity

Two-Dimensional NMR Spectra of Isotactic Poly(methyl methacrylate) Prepared with t-C4H9MgBr and Detailed Examination of Tacticity

Another example of carborane based trianionic ligand: Syntheses and catalytic activities of cyclohexylamino tailed ortho-carboranyl zirconium and titanium dicarbollides

Carbon-13 NMR chemical shift assignments of poly(vinyl chloride) based on the 2D-INADEQUATE spectrum

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