摘要:

The copolymerization reactivity ratios for styrene/m- and styrene/p-divinylbenzene have been determined at high conversions (<35%) using the integrated form of the copolymerization equation. Values of r1(s) = 1.11, r2(m) = 1.00; and r1(s) = 0.20, r2(p) = 1.00 were obtained. These values indicate the same relative behavior but are quantitatively different from the differential data. The data confirm that the para isomer is incorporated more rapidly into the growing polymer chain than is the meta isomer.

ISSN:0022-233X    

DOI:10.1080/00222337008069362

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Under carbon monoxide pressure, cupric alkoxides such as cupric methoxide, Cu(OCH3)2, and cupric acetylacetonate methoxide, Cu(acac)(OCH3), initiate the polymerization of vinyl monomers. The microstructure of polybutadiene and the composition of styrene-methacrylate copolymer by these catalyst systems have indicated a free radical mechanism. The mechanism of the initiation was examined by the end group of product polymer and the analysis of the reaction between the catalyst components. Reduction of Cu(OCH3)2and Cu(acac)(OCH3) with carbon monoxide to Cu(OCH3) and Cu(acac), respectively, was responsible for the initiating activity. The decomposition of these unstable cuprous species produces methoxyl and acetylacetonyl radicals which initiate the polymerization.

ISSN:0022-233X    

DOI:10.1080/00222337008069363

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Methacrylamide polymerizes in the solid state in a manner analogous to acrylamide; i.e., the polymer nucleates as a second phase during reaction. However, in this case, the reaction is sensitive to the presence of reactive gases. These gases are presumed to diffuse along surfaces, lattice defects, and the monomer-polymer interface. Nitric oxide and sulfur dioxide inhibits both the in-source and postirradiation polymerization. Oxygen behaves anomalously. It inhibits the postirradiation reaction, but accelerates the in-source one. It apparently does this by shortening the induction period. A possible mechanism is suggested.

ISSN:0022-233X    

DOI:10.1080/00222337008069364

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Long-chain branching can occur during radical polymerization and is especially important for polyethylene. An improved method of calculating the effect of long-chain branching on molecular weight distribution is presented. This method uses a probability treatment. The results are more consistent with both kinetic theory and experimental data than the results of previous long-chain branching calculations. In contrast to previous calculations, the present work shows that generation cannot occur from long-chain branching alone.

ISSN:0022-233X    

DOI:10.1080/00222337008069365

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The copolymerization of styrene and methyl methacrylate in the presence of ethylaluminum sesquichloride in toluene yields alternating copoly-mers, independent of initial monomer ratio. The rate of polymerization is not influenced by the presence of an excess of either monomer, the conversion curves following a parallel course at a given total monomer concentration. When the concentration of the AlEt1.5Cl1.5and the S/MMA ratio are kept constant and the total monomer concentration is increased, the polymerization rate increases and reaches a limiting value at a S/MMA/Al ratio of 2:2:1. A similar result is obtained when the total monomer and the AlEt1.5Cl1.5concentrations are kept constant and the S/MMA ratio is varied. When the concentration of either monomer and the AlEt1.5Cl1.5concentration are kept constant and the concentration of the other monomer is varied, the polymerization rate reaches a limiting value at the same mole ratio, irrespective of which monomer is varied. The rate of polymerization is decreased in the presence of a small amount as well as a large amount of benzoquinone. However, the rate is higher than in the absence of the quinone when the Al/benzoquinone ratio is 2:1. The conductivity of a toluene solution of AlEt1.5Cl1.5increases only slightly upon the addition of methyl methacrylate, a further small increase occurring upon the addition of styrene. The results provide evidence for the participation of a comonomer complex in the polymerization, the optimum composition resulting either from the simultaneous interaction of several equilibria or the alignment of the complexes in the form of a matrix.

ISSN:0022-233X    

DOI:10.1080/00222337008069366

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The kinetic features of the copolymerization of styrene and methyl methacrylate in the presence of ethylaluminum sesquichloride in toluene do not unequivocally distinguish between first- and second-order reactions. The reaction does not attain steady-state conditions. The course of the reaction is apparently influenced by many factors including the dissociation of the polymerizable complex into unreactive monomeric species and physical phenomena such as diffusion and dilution effects as well as matrix formation. The use of azobisisobutyronitrile as an initiator indicates apparent bimolecu-lar termination but the kinetic curves show deviation from linearity.

ISSN:0022-233X    

DOI:10.1080/00222337008069367

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The polymerization of isoprene in aromatic solvents, catalyzed by an ethylaluminum dichloride-titanium tetrachloride system, proceeds via a complex of the monomer with the catalyst, chain growth occurring when a monomer cation-radical is formed through the transfer of one electron from the monomer to the catalyst. The deactivation of the active species results from the dissociation of the complex polymer cation-radical to free ions. The over-all reaction is a nonstationary process during which the concentration of free ions increases and the concentration of the active species decreases. A reaction mechanism is proposed which leads to kinetic expressions that quantitatively describe the experimental data.

ISSN:0022-233X    

DOI:10.1080/00222337008069368

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Through the use of a Ti(OR′)4-AlRCl2catalyst system, high 1,4-cis isoprene polymers and crystalline 1,4-trans polybutadiene are obtained. Neither monomer is polymerized at a Al/Ti mole ratio of less than 4. The maximum activity and stereospecificity for isoprene is observed at Al/Ti = 4. For 1,4-trans butadiene polymers the activity increases progressively with increasing Al/Ti ratio. The investigations carried out on this catalyst system show that at a AI/Ti mole ratio of 4 the formation of crystalline β-TiCl3takes place, while at lower ratios insoluble chloro-alkoxide derivatives of TiIIIwith different compositions separate. Soluble complexes containing aluminium and titanium are initially formed before precipitation occurs. Chemical data and investigations by IR and NMR spectroscopy indicate exchange reactions between Al-Cl, Al-R, and Ti-OR groups, together with reduction of the transition metal. A reaction mechanism and a hypothesis on the nature of the active catalyst are given.

ISSN:0022-233X    

DOI:10.1080/00222337008069369

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

Epoxidations with peracetic acid were effected on a series of alkyllithium and sodium polybutadienes, and the properties of the epoxy resins were compared. The alkyllithium and sodium polybutadienes differed in micro-structure and molecular weight distribution. The alkyllithium polybutadienes were more readily epoxidized, and epoxidation resulted in dramatically lower viscosity increases with increasing epoxy contents. Epoxidized alkyllithium polybutadienes varying in molecular weight and epoxy content were shown to be compatible, efficient, and permanent plasticizer-stabilizers for polyvinyl chloride.

ISSN:0022-233X    

DOI:10.1080/00222337008069370

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor

摘要:

The oxidation of polybenzimidazolone and selected model compounds including compounds containing benzimidazole and benzimide ring systems has been investigated at temperatures from ambient to 700°C. Residue elemental analyses, volatile product distribution differences as a function of time and oxidation temperature, thermogravimetry, and differential thermal analysis studies are reported. The determination of the energy of activation for the over-all initial oxidation processes over the ranges of 0 to 15% weight loss and 100 to 700°C indicated a value of 35.5 kcal/mole. The elemental analyses data indicate that significant differences in residue composition exists between model compounds having aminederived end groups and those systems bearing acid-derived end groups. Data obtained using differential thermal analyses techniques indicate little difference in the thermal behavior of the benzimidazolones in inert or oxygen atmospheres. The changes in the amounts of carbon dioxide and carbon monoxide as a function of temperature and time support a proposal for simultaneous thermal and thermooxidation processes for the degradation of these systems in oxygen atmospheres at high temperatures.

ISSN:0022-233X    

DOI:10.1080/00222337008069371

出版商:Taylor & Francis Group    

年代:1970

数据来源: Taylor