摘要:

The synthesis of oligomeric tin poly(cobalticinium esters) is presented as a function of the particular reaction variables stirring rate, pH and amount of added base, mole ratio of reactants, concentration of reactants, and volume of organic phase. Factors which decrease the solubility of the stannane apparently act to increase the yield of polyester. The thermal characterization of I was carried out via DSC and TGA. The products generally exhibit endotherms below 150 to 200[ddot]C which may be related to Tg. Above 200[ddot]C, degradation occurs in air by an oxidative mode.

ISSN:0022-233X    

DOI:10.1080/00222337408066416

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The chlorine substitution reaction of trimeric dichlorocyclophosphazene with sodium hydrosulfide has been examined. The reaction proceeded easily in dioxane and THF solutions. The reaction product, which had the chemical composition P3N3S6H6, was examined by31P-NMR and IR spectroscopy. Further, it is suggested that the product was polymerized by heating with hydrogen sulfide, and the polymer (PNS) was formed.

ISSN:0022-233X    

DOI:10.1080/00222337408066417

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The dyad and triad tacticities of polypropylenes were determined quantitatively with the aid of a computer form the 100-MHz proton magnetic resonance spectra in o-dichlorobenzene solution at 165[ddot]C. The contents of tactic dyad and traid evaluated from the 100-MHz PMR spectra are in fair agreement with the values determined from the 220-MHz PMR and13C-(1H) spectra, respectively. The fraction soluble in boiling ethyl ether of polymer prepared with the Ti(O-n-Bu)Cl3-AlEt2Cl catalyst shows a character of stereorandomness, and the ethyl ether-soluble portion of polymer polymerized with the TiCl3-AlEt2Cl catalyst has a character of stereoblock sequence. Furthermore, by IR analysis, it has become apparent that the former has a (CH2)2group formed by two propylene units in a tail-to-tail arrangement.

ISSN:0022-233X    

DOI:10.1080/00222337408066418

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

When protein in various atmospheres such as N2, O2, H2, CO2, and NH3is irradiated by γ rays form a60Co source, the changes in the internal relationships of the atoms in the protein molecule vary with the gases composing the irradiation atmosphere. An empirical equation for the optical rotation was obtained. Protein irradiated by γ rays showed the effect of temperature by changes in the internal relationships of the atoms in the protein molecule. An empirical equation for the optical rotation was obtained. The behavior of optical rotation shows a similar dependence on irradiation atmosphere and temperature as shown in earlier viscosity experiments.

ISSN:0022-233X    

DOI:10.1080/00222337408066419

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Head-to-head poly(methyl acrylate) was prepared by esterification of the known alternating copolymer of ethylene and maleic anhydride. Some of the chemical,physical, and mechanical properties and the thermal degradation behavior of head-to-head poly(methyl acrylate) were studied and compared with those of head-to-tail poly(methyl acrylate). The Tgof the head-to-head polymer was higher than that of the head-to-tail polymer, but the solubilities of both types of polymers of comparable molecular weight were similar. Head-to-head poly(methyl acrylate) degraded thermally at approximately the same temperature and with a rate similar to head-to-tail poly(methyl acrylate). Unlike poly(methyl cinnamates) which cleanly degraded to monomers, poly(methyl acrylates), head-to-head and head-to-tail, degrade to very small molecules, such as CO2, methanol, but also larger polymer fragments and char. Trace amounts of monomers (methyl acrylate) were also observed.

ISSN:0022-233X    

DOI:10.1080/00222337408066420

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Acid (HCL) catalyzed methanolysis of polyvinyl acetate and of model compounds was carried out in solvent mixtures with various amounts of methanol and tetrahydrofuran. The initial rate was first order vs methanol concentration. The acceleration was mainly dependent on the extension of the chain and was enhanced by a tighter coiling of the macromolecule; it is suggested that coiling favors the trapping of the catalyst ions.

ISSN:0022-233X    

DOI:10.1080/00222337408066421

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Acid (HCL) catalyzed methanolysis of vinyl acetate-vinyl chloride copolymers was carried out in solvent mixtures with various amounts of methanol and tetrahydrofuran. The effect of the sovent composition on the initial rate suggests the existence of preferential solvation. The initial rate may be explained in terms of sequence distribution. The acceleration noted in polyvinyl acetate homopolymers disappears as soon as the vinyl chloride content is higher than 30±.

ISSN:0022-233X    

DOI:10.1080/00222337408066422

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

Kinetic deviations from the Lewis and Mayo theory for the radical copolymerization of acrylonitrile and vinyl chloride reported previously are tentatively interpreted as a consequence of an internal transfer reaction involving the tertiary hydrogen atom of an antepenultimate acrylonitrile unit. Although the deviations disappear if acrylonitrile is replaced by methacrylonitrile, this interpretation is far from being quantitatively satisfactory. Another explanation seems to be better: it involves intramolecular copolymerization with C˭N triple bonds producing a cyclic imine radical which gives rise to coloration of the copolymer and causes the formation of new C˭N.radicals with low reactivity vs propagation reactions.

ISSN:0022-233X    

DOI:10.1080/00222337408066423

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

The experimental determination of the activity of silicalumina-based chromium oxide catalyst vs propypene polymerization at low monomer pressure is discussed. A reduction pretreatment of the catalyst under optimal conditions is necessary to obtain an activity stable enough to be accurately measured. Surface area measurements show that it remains a noticeable activity at subzero temperature.

ISSN:0022-233X    

DOI:10.1080/00222337408066424

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor

摘要:

It is shown that the new model of an active site of chromium oxide catalyst supported on silica-alumina, previously proposed for ethylene polymerization, is also valid for propylene polymerization. The new model involves a set of three chromium atoms with different oxidation degrees located at the border of the flat chromium oxide domains spread onto the support. The main differences between the behavior of the two monomers are caused by the much higher reducing power of the propylene and also by its mode of adsorption which is stronger. Some copolymerization experiments are described.

ISSN:0022-233X    

DOI:10.1080/00222337408066425

出版商:Taylor & Francis Group    

年代:1974

数据来源: Taylor