Hochaufgelösle kernresonanzspektren von polyvinylchlorid

Johnsen, U.

doi:10.1002/pol.1961.1205415923

Cited by 61 publications

(14 citation statements)

References 2 publications

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“…following a suggestion of Flory and Fox8 have recently discussed the glass transition temperature of non-polymeric liquids as occurring when a critical ratio of free volume to total volume is reached in the liquid. They have demonstrated that for many liquids the glass transition occurs at about the same value of a reduced temperature given by (1) where h, is the molar latent heat of evaporation of the liquid. According to the Prigogine theory the volume of the pure polymeric liquid is a function of a reduced temperature (eq.…”

Section: Received June 25 1062mentioning

confidence: 99%

On determination of the tacticity of polyvinyl chloride from high resolution NMR spectra

Tincher¹

1962

J. Polym. Sci.

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An analysis of the high resolution nuclear magnetic resonance spectrum of polyv ngl chloride which yields the number of isotactic and syndiotactic diads has been reported by Johnsen.' This analysis was based on the assumption that the magnetic environment of the methylene protons in an isotactic unit is different from the magnetic environment of the methylene protons in a syndiotactic unit. Spin coupling with the protons on the two adjacent carbon atoms would therefore give a pair of triplets for the resonance spectrum of the methylene protons. The observed resonance spectrum of this group was decomposed by Johnsen into a pair of overlapping triplets and the triplet at higher field was arbitrarily assigned to methylene protons in syndiotactic units. The relative number of isotactic and syndiotactic units was then determined from the areas of the two triplets. On this baeis the sample of polyvinyl chloride which he investigated was found to contain 64% syndiotactic and 36% isotactic units.Johnsen's analysis of the spectrum of polyvinyl chloride assumes that the magnetic environments of the two methylene protons in an isotactic unit are equivalent. However, careful study of the geometrical arrangements of the groups in models of the polyvinyl chloride chain strongly indicates that equivalency of the methylene protons in isotactic units is unlikely. It is also significant that analyses of the NMR spectra of other poly-

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Section: Received June 25 1062mentioning

confidence: 99%

On determination of the tacticity of polyvinyl chloride from high resolution NMR spectra

Tincher¹

1962

J. Polym. Sci.

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“…Since is and si are mirror images, we conclude: Such relationship enables us to convert higher order sequence tacticities to lower ones, for example : P(s) = P(ss) + P (si) : . S = s + h/2 (6) and…”

Section: For Triadsmentioning

confidence: 99%

“…Nomenclature syndiotactic placement; also triad syndiotacticity isotactic placement; also triad isotacticity triad heterotacticity diad syndiotacticity diad isotacticity normalized probability reaction rate constant universal gas constant parameters defined by eqs. (14), (15) ratio r1/rZ absolute temperature, O K differential enthalpy change (kinetic) differential enthalpy change (thermodynamic) differential entropy c.hange (kinetic) variance GTeek Symbols P, 9 persistence ratios 7 , 6 chemical shifts, ppm…”

Section: Arrhenius Relationshipmentioning

confidence: 99%

Nuclear magnetic resonance and stereoregularity of PVC

Abdel-Alim

1975

J of Applied Polymer Sci

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SynopsisThe decoupled a-proton spectrum of PVC was examined using a 220 MHz NMR spectrometer. All of the ten possible pentads were detected and an assignment is given based on Bernoullian statistics. This assignment is in general agreement with conclusions reached by previous workers except for some modifications in the heterotactic resonances. Triad tacticity data were obtained from the pentads and were used to estimate the differential enthalpy and entropy changes for bulk PVC polymerized in the temperature range 70°C to -50°C. THEORY Chain Sequence StereoregularityWhen a vinyl chloride monomer unit adds on to a growing chain during freeradical polymerization in a tail-to-head fashion, the carbon-carbon bond of this molecule still rotates even after the molecule tail (CH2-) has been attached. The chlorine atom assumes different spatial positions due to this rotation, and its configuration relative to the rest of the chain is undefined until the next monomer unit adds on. When this happens, the configuration of that particular chlorine atom is fixed. Whether there is or there is not any influence of this configuration on the configuration of the next chlorine atom is a matter of the statistical pattern of addition. Basically, there are two possible configurations for the chlorine atom. If it lies to the same side of the zigzag chain as the preceding chlorine, an isotactic placement has occurred. If it lies opposite to the preceding one, a syndiotactic placement has occurred. Subsequent additions may result in the same configuration or a switch can take place. Figure 1 is a schematic representation of the possible configurations that result from the stepwise addition of four monomer units. Sequences made up of two monomer units are called diads, those of three units are called triads, four monomer units are called tetrads, five are called pentads, and so on. As shown in the figure in triads and higher sequences, we can define a third configuration called heterotactic. This may not be called heterotactic placement. There are only two possible placements, i.e., isotactic and syndiotactic and that is strictly correct for diads. For higher sequences, the word configuration should be used rather than placement. At the bottom of the figure, the possible number of each of the three configurations is shown and also the total number of configurations possible for any sequence length. Thus, there are two diads, three triad configurations, six tetrads, and ten pentads. It'should be noted

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“…Five peaks are observed clearly in the resonance lines due to methylene protons, while the lines corresponding to methyne protons consist of more than seven peaks instead of a quintet as reported by Johnsen and Tincher. Two possibilities will be considered for the origin of the observed seven methyne lines: (1) these lines are composed of more than two overlapping multiplets, or (2) these lines cannot be expressed by an A part of AX4 system. I n contrast to the complicated patterns given by indirect spin-spin interactions between methylene protons and/or between methylene and methyne protons, the spectra obtained by the spin-decoupling technique are much simpler but more reliable for use in analysis of the spectra.…”

Section: Poly(viny1 Chloride)mentioning

confidence: 99%

Undecoupled and decoupled high resolution nuclear magnetic resonance study of poly(vinyl chloride)

Satoh

1964

J. Polym. Sci. A Gen. Pap.

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High resolution nuclear magnetic resonance spectra of two kinds of poly(vinyl chloride) and the model compounds, meso and racemic 2,4‐dichloropentane were studied by normal and spin decoupling technique to elucidate the polymer structure. Unlike the methylene resonance of meso 2,4‐dichloropentane which has been observed as an AB type quartet, only a singlet has been observed as the methylene resonance in isotactic sequences of poly(vinyl chloride) in spin‐decoupled spectra. Two peaks of decoupled spectra of the polymer at 7.76 and 7.96 τ are due to methylene protons in isotactic and syndiotactic sequences in the diad, respectively, and the other three peaks at 5.43, 5.53, and 5.69τ correspond, respectively, to syndiotactic, heterotactic, and isotactic units in the triad. By analyzing decoupled spectra of the two kinds of polymer, parameters of local regularity have been determined. A theoretical treatment for the spectrum for four nuclei ABX2 has been applied to analysis of the methylene resonance of meso 2,4‐dichloropentane.

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Hochaufgelösle kernresonanzspektren von polyvinylchlorid

Cited by 61 publications

References 2 publications

On determination of the tacticity of polyvinyl chloride from high resolution NMR spectra

On determination of the tacticity of polyvinyl chloride from high resolution NMR spectra

Nuclear magnetic resonance and stereoregularity of PVC

Undecoupled and decoupled high resolution nuclear magnetic resonance study of poly(vinyl chloride)

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