Molecular weight distribution of polyethylene produced by radiation polymerization in a heterogeneous system

Watanabe, Terutaka; Wada, Takehiko; Machi, Sueo; Takehisa, Masaaki

doi:10.1002/pol.1972.110100916

Cited by 14 publications

(3 citation statements)

References 7 publications

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“…These could allow the polymerization to proceed in two different physical states and with varying mobility in the polymer chains. As a result, the polymers are formed with differing molecular weights [9]. This may be a consequence of the harsh reaction conditions due to the use of MAO as an activator and methylating agent [10].…”

Section: Organotitanium Carbohydrate Compounds For Use In Catalytic Rmentioning

confidence: 99%

Monosaccharide Ligands in Organotitanium and Organozirconium Chemistry

Kitaev

Zeysing

Heck

2009

Activating Unreactive Substrates

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Despite their advantageous properties, monosaccharide-derived ligands have rarely been applied in the synthesis of organometallic compounds and thus little is known about their coordination capabilities. Most of the established monosaccharide-metal complexes are based on late transition metals such as Rh, Pd and Pt [1]. Among early transition metals, monosaccharide complexes containing Ti and Zr are of importance [2]. Although the information pertaining to their metal-ligand binding sites is scarce, both late and early transition metal complexes of modified monosaccharides have been successfully applied as chiral reagents and catalysts in stereoselective synthesis [3]. Synthesis of Organotitanium Carbohydrate CompoundsWithin this research topic we are interested in the ability of pyranosides to coordinate to varying titanium precursors and the use of the resulting complexes in stereoselective synthesis. In particular we are investigating the 2-and 3-positions of pyranosides as coordination sites for organometallic complexes of the early transition metal Ti. The torsion angle between the oxygen functions of C2 and C3 of the pyranosidato ligand may determine whether a mononuclear chelate complex or a dinuclear compound with a bridging coordination between two Ti atoms is formed.Our interest in the coordination chemistry of Ti when reacted with carbohydrate ligands has led to previously reported reactions [4,5]. The reaction of methyl-4,6-Obenzylidene-b-D-glucopyranoside (b-MeBnGluH 2 ) with the organotitanium complex Cp Ã TiCl 3 in the presence of triethylamine gave the dinuclear titanium complex (T-4-R; T-4-R)bis[chlorido(h 5 -pentamethylcyclopentadienyl)][m-(methyl-4,6-O-benzylidene-b-D-glucopyranosidato-1kO 2 , 2kO 3 )][m-(methyl-4,6-O-benzylidene-b-D-glucopyranosiActivating Unreactive Substrates: The Role of Secondary Interactions. Edited

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Section: Organotitanium Carbohydrate Compounds For Use In Catalytic Rmentioning

confidence: 99%

Monosaccharide Ligands in Organotitanium and Organozirconium Chemistry

Kitaev

Zeysing

Heck

2009

Activating Unreactive Substrates

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“…The molecular weight of polymer formed in tert-butyl alcohol was also much higher than that of polymers obtained in ethyl alcohol and in n-butyl alcohol. The number of polymer chains in these three systems increased slight.ly under 80°C and markedly above 80°C with increasing the tempora- [9][10][11][12][13][14] show the results obtained in various hydrocarbons such as cyclohexane, 2,2,4-trimethylpentane, and 2,2,5-trimethylhcxane. In cyclehexanc ( Fig.…”

Section: )mentioning

confidence: 99%

Effect of temperature on the radiation‐induced polymerization of ethylene in various media

Wada

Watanabe

Takehisa

et al. 1974

J. Polym. Sci. Polym. Chem. Ed.

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The effects of temperature on the radiation‐induced polymerization of ethylene in bulk and in the presence of ethyl alcohol, n‐butyl alcohol, tert‐butyl alcohol, cyclohexane, 2,2,4‐trimethylpentane, and 2,2,5‐trimethylhexane were studied. The changes of the amounts of polymerized monomer with the reaction temperature were different from each other in these reaction systems, especially in the range lower than 60–80°C. At temperatures lower than 60–80°C, as the reaction temperature increases, the amount of polymerized monomer decreased in bulk and in the presence of tert‐butyl alcohol. The amount was almost constant in the presence of ethyl alcohol and 2,2,4‐trimethylpentane, and it increased in the presence of n‐butyl alcohol, cyclohexane, and 2,2,5‐trimethylhexane. However, in the temperature range higher than 60–80°C, the amount of polymerized monomer increased with increasing temperature in every reaction system except for bulk polymerization. The molecular weight of polymer decreased with increasing temperature in every reaction system except at temperatures lower than 25°C. The molecular weight of polymer formed in bulk, in tert‐butyl alcohol, and also in 2,2,4‐trimethylpentane were relatively higher than that in other reaction systems. A bimodal molecular weight distribution was observed for the polymer formed in bulk and in tert‐butyl alcohol at 40–60°C. These results are discussed in connection with the heterogeneity of the reaction system. The differences due to temperature in each reaction system are explained as due to the difference in affinity of the reaction system for the propagating chain and in the facility of chain transfer to the medium.

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“…3. Molecular weight distribution of poly(methyl methacrylate) produced by radiation-induced heterogeneous polymerization a t various temperatures: (1 ) 0°C; (8) Table 111. The polymer yield, the molecular weight of polymer, and the number of polymer chains N , are plotted against the monomer concentration in Figures 4 and 5.…”

Section: Molecular Weightmentioning

confidence: 99%

Radiation‐induced heterogeneous polymerization of methyl methacrylate in precipitants

Wada

Takehisa

Machi

1974

J. Polym. Sci. Polym. Chem. Ed.

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The radiation‐induced heterogeneous polymerization of methyl methacrylate in various precipitants, mainly methyl alcohol, was carried out, and the effects of reaction conditions on the polymerization behavior and the molecular weight distribution of polymer were studied. Bimodal molecular weight distributions were found for the polymer produced by the heterogeneous polymerizations in methyl alcohol and in tert‐butyl alcohol. The apparent activation energy is 1.0 and 4.5 kcal/mole, respectively, for the polymerization at a monomer concentration of 10 vol‐% in methyl alcohol above and below 35°C. The polymerization at a monomer concentration lower than 40 vol‐% in methyl alcohol proceeded with the precipitation of polymer. The dose rate exponent of the mean rate of heterogeneous polymerization decreased from 0.5 to a smaller value as the polymerization progressed. The ratio of the two peaks in the bimodal molecular weight distributions of polymer produced in methyl alcohol was affected by the reaction conditions. These results show the coexistence in the polymerizations of two different physical states of propagating chain, a loose state and a rigid one. The reaction scheme is discussed in connection with the physical factors which affect the solubility or the mobility of propagating chains, and the rate of elementary reactions, which influences the degree of propagating chains.

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Molecular weight distribution of polyethylene produced by radiation polymerization in a heterogeneous system

Cited by 14 publications

References 7 publications

Monosaccharide Ligands in Organotitanium and Organozirconium Chemistry

Monosaccharide Ligands in Organotitanium and Organozirconium Chemistry

Effect of temperature on the radiation‐induced polymerization of ethylene in various media

Radiation‐induced heterogeneous polymerization of methyl methacrylate in precipitants

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