Tacticity measurement of polymethacrylate by peak-eliminated fourier-transform NMR
Department of Chemistry, Osaka University, Suika, Ōsaka, JapanJournal of Polymer Science Polymer Letters Edition 09/1976; 14(9):531-535. DOI: 10.1002/pol.1976.130140904
A number of works have centered on the structural determinations of macromolecules by using Fourier-transform NMR. However, in the PMR study of large biological molecules there are a variety of problems owing to a large residual HDO peak. Recently, water-eliminated Fourier-transform (WEFT) NMR was developed to overcome these problems and was applied to the study of biological molecules. In the reported work, the principle of WEFT method was successfully applied to the analysis of the tacticity of poly(alkyl methacrylate). The spectra of syndiotactic PMMA were measured in toluene-d//8 at 110 degree C by a pulse sequence of (180 degree minus t minus 90 degree minus 10 sec)//4 at various values of t, and the triad tacticities were determined from the intensity measurements of the three alpha -methyl peaks. The results are tabulated. The tacticities of several poly(alkyl methacrylates) were successfully determined by the peak-elimination method, and the results are shown. Agreement between the observed and the calculated dyad tacticities also shows the accuracy of the measurements.
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ABSTRACT: Copolymer of methyl methacrylate-d8(M1) with a small amount of trityl methacrylate(M2) was radically prepared in tetrahydrofuran and converted into the copolymer of methyl methacrylate-d8 with a small amount of undeuterated methyl methacrylate by the selective hydrolysis of the trityl group and subsequent methylation with diazomethane. From the 1H NMR spectrum of the derived copolymer the assigned coisotactic parameters s12 and s21 were determined to be 0.14 and 0.61, respectively. This may be the first example of the unequivocal determination of assigned configurational parameters in cross propagation for copolymerization.Polymer Bulletin 09/1978; 1(2):97-102. DOI:10.1007/BF00255721 · 1.44 Impact Factor
- Macromolecules 03/1979; 12(2):234-239. DOI:10.1021/ma60068a012 · 5.80 Impact Factor
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ABSTRACT: Polymerizations of ethyl methacrylate were carried out in toluene with butyllithium at various temperatures. The polymer obtained at −78°C could be fractionated into methanol-insoluble and methanol-soluble fractions. The former was rather syndiotactic. The latter was found by gel-permeation chromatography and 1H NMR spectroscopy to be composed of highly isotactic polymer and isotactic oligomer. These three fractions were formed simultaneously at the beginning of the polymerization and the amounts and molecular weights of the isotactic and syndiotactic fractions increased during the polymerization, while the amount of oligomeric fraction remained almost constant after the initial rapid increase. These results indicate the coexistence of three different active species for isotactic and syndiotactic polymers and isotactic oligomer, respectively, at the initial stage of the polymerization and two propagating species during the polymerization. The amounts of syndiotactic fraction and oligomeric fraction decreased with an increase in the polymerization temperature and only the isotactic polymer was obtained above −20°C. When the polymerization was initiated with 1,1-diphenylhexyllithium, only an isotactic polymer was produced. In the polymerization initiated with butyllithium, an appreciable amount of lithium ethoxide formed at the initial stage of the reaction, but no formation of the ethoxide was observed in the case of 1,1-diphenylhexyllithium. This indicates that the multiplicity of the active species in the polymerization with butyllithium is strongly related to the lithium ethoxide formed.Polymer Journal 12/1979; 11(12):989-994. DOI:10.1295/polymj.11.989 · 1.65 Impact Factor
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