The carbon-13 high resolution nuclear magnetic resonance spectra with proton spin decoupling of polystyrene and poly-a-methylstyrene were measured. The spectra clearly split corresponding to triad, tetrad, and partially pentad placements, and these peaks were tentatively assigned. By comparison of the triad tacticity of poly-a-methylstyrene deteLmined from carbon-I3 spectra with that from proton spectra, it was confirmed that the nuclear OVERHAUSER effect due to proton decoupling has little effect on the relative intensities of the peaks assigned to chemically equivalent carbons except for stereochemical configuration.The stereospecific polymerization mechanisms are discussed on the basis of the microtacticity determined from carbon-13 spectra. As a result, it is concluded that poly-a-methylstyrene polymerized with cationic and anionic catalysts can be described by BERNOULLIAN statistics, while the atactic polystyrene does not obey BERNOULLIAK but first or second order MARKOVIAN statistics. ZUSAMMENFASSUNG:Hochaufgeloste 13C-NMR-Spektren von Polystyrol und Poly-a-methylstyrol werden unter Bedingnng der 1H-Spinentkopplung aufgenommen. Die Spektren zeigen klare Aufspaltungen, die den Triaden, Tetraden und teilweise den Pentaden entsprechen ; die verschiedenen Signale werden versuchsweise zugeordnet. Durch Vergleich der Triaden-Taktizitaten von Poly-a-methylstyrol auf Grund der 13C-NMR-Spektren mit den Protonea-Spektren konnte gezeigt werden, daB der OVERHAUSER-Effekt die relativen Intensitaten der Signale von chemisch aquivalenten Kohlenstoffatomen nur wenig beeinfluBt, mit Ausnahme bei der stereocbemischen Konfiguration.Die Mechanismen der stereospezifischen Polymerisation werden auf der Grundlage der durch W-NMR bestimmten Mikrotaktizitat dlskutiert. Die kationische und die anionische Polymerisation von a-Methylstyrol kann durch die BERNOULLI-Statistik beschrieben werden, wogegen das ataktische Polystyrol der MARKOV-Statistik gehorcht.

The stereoregular polymerization of methyl methacrylate by Grignard reagents as affected by various alkyl groups, polymerization temperatures, and organic additives has been studied. These three factors were found to be effective in controlling the stereoregularity of PMMA. It has been confirmed that bands sensitive to stereoregularity at 757 and 749 cm.−1 correspond to isotactic and syndiotactic segments, respectively. Isotaxy and syndiotaxy were determined by the infrared method. Proton magnetic resonance spectra were found to be useful in analyzing the stereoregularity of PMMA and in estimating the amounts of stereoregular components in the polymer chains. Three elementary stereoregular units were proposed: isotactic, syndiotactic, and disyndiotactic. The kinetics of the polymerization reactions were studied in the cases of n‐butyl and isobutyl magnesium bromide. The rates of polymerization were found to be proportional to monomer concentration and to the square of the initiator concentration and molecular weight was proportional to monomer concentration and inversely proportional to initiator concentration. The rate of polymerization is maximum at a certain temperature. Branched‐alkyl Grignard reagents were found to produce isotactic polymer. Straight‐chain, alkyl‐type Grignard reagents, with the exceptions of n‐octyl‐ and n‐hexylmagnesium bromide, produce usually stereoblock polymer. Phenylmagnesium bromide (above 0°C.) and cyclohexylmagnesium bromide produce isotactic polymer. Low‐temperature, free‐radical polymerization results in almost wholly syndiotactic polymer. Ordinary free‐radical polymer has a stereoblock strucutre composed of syndiotactic and disynodiotactic units with smaller amounts of isotactic material. The addition of dioxane, pyridine, diphenylamine, or diethylamine promotes polymerization. Use of the latter two amines results in isotactic polymer.

Proton‐decoupled, partially relaxed, Fourier‐transform NMR of 13C in natural abundance was used to determine spin‐lattice relaxation times of individual carbons of polyisobutylene, polyacrylonitrile, poly(vinyl chloride), and poly(vinyl alcohol) in solution. It is shown that the relaxation times are independent of the difference in stereochemical configuration. From the values of the nuclear Overhauser enhancement factor it is shown that the relaxation times are independent of the difference in stereochemical configuration. From the values of the nuclear Overhauser enhancement factor it is shown that the excess spin energy from equilibration of all the 13C, even of quaternary carbons, in the polymers dealt with here is transferred to the lattice mainly through 13C‐1H dipolar interactions. It is shown that the segmental motions responsible for the spin‐lattice relaxation of the polymer skeleton in solution can be described by the isotropic model within a good approximation, except for poly(vinyl alcohol) at low temperature. The activation energies of skeletal and internal methyl motions are estimated from the temperature dependence of the correlation time. Differences in the 13C line widths for individual carbons of polyisobutylene are discussed briefly.

The 13C-{1H} high-resolution nuclear magnetic resonance spectra were measured for poly(methyl methacrylate). The spectra clearly split corresponding to dyad, triad, tetrad, and pentad placements. The relative intensity of every peak for the spectrum of a polymer prepared with 9-fluorenyllithium in tetrahydrofuran/toluene (80/20) at -23°C was reasonably interpreted by the Bernoulli trial model.The nuclear Overhauser effect due to total proton decoupling did not affect the relative intensities among the peaks assigned to chemically equivalent carbons except for the difference in stereochemical configuration. This was confirmed by comparison between the relative intensities of the above-mentioned polymer and by comparison between those of 13 C-{1H} and of 1H resonance of the polymer.The microtacticity determined by 13C-{1H} spectra of a polymer prepared with 9-fluorenyllithium in tetrahydrofuran/toluene (4/96) was fairly well interpreted by the stereoblend model, but by neither first-order nor second-order Markovian model. KEY WORDSPoly(methyl methacrylate) / 13C-{1H} NMR / Stereoblend / Markovian Model/ Bernoullian Model / Nuclear Overhauser Effect /

Proton-decoupled partially relaxed FOURIER transform (PRFT) NMR of 13C in natural abundance was used to determine spin-lattice relaxation times (TI) of individual carbons of polypropylene and polyethylene in o-dichlorobenzene solution and molten polyethylene. It is shown that the relaxation times of polypropylene carbons are independent of the difference in stereochemical configuration. From the values of the nuclear OVERHAUSER enhancement factor it is shown that the excess energy from equilibrium of all 13C in polypropylene and polyethylene are absorbed into lattice mainly through W -l H dipolar interactions. It is shown that the effective rotational motion of the skeletal carbons in polypropylene is isotropic. The activation energies of skeletal and internal methyl motions in polypropylene, separately, and skeletal motion in polyethylen in solutions were estimated from the temperature dependence of the correlation time. The assignment of the two peaks appearing in methine carbon region of polypropylene was briefly discussed. ZUSAMMENFASSUNG:Protonenentkoppelte PRFT-NMR Spektren von naturlich vorkommendem 13C wurden zur Bestimmung von Spin-Gitter-Relaxationszeiten (TI) bestimmter Kohlenstoffatome des Polypropylens und Polyathylens in o-Dichlorbenzol-Losung und in geschmolzenem Polyathylen verwendet. Es wird gezeigt, daB die Relaxationszeiten der Polypropylen-Kohlenstoffe von Konfigurations-Unterschieden unabhangig sind. Mit Hilfe der Werte des OVERHAUSER-VerStarkungSfaktorS wird gezeigt, daB die oberschul3-Energie aus dem Gleichgewicht aller 1% in Polypropylen und Polyathylen vom Gitter aufgenommen wird, und zwar hauptsachlich durch 13C-lH-dipolare Wechselwirkungen. Es wird auoerdem die Isotropie der effektiven Rotations-Schwingung der Kohlenstoff-Skelette im Polypropylen aufgezeigt. Die Aktivierungsenergien der Skelett-und der internen Methyl-Schwingungen im Propylen selbst und die Skelett-Schwingungen im Polyathylen in Losung wurden aus der Temperaturabhangigkeit der Korrelationszeit abgeschatzt. Die Zuordnung der beiden Peaks, die im Bereich des Methin-Kohlenstoffs von Polypropylen erscheinen, wurde kurz diskutiert.*) cf.4); this paper is considered to be Part 1 of this series.