摘要:

Beta-cyclodextrin/poly(vinylidene chloride) adduct (beta-CD-PVDC), after dehydrochlorination, and beta-CD/vinylidene chloride-allyl chloride copolymer result in unit cell crystals in which the beta-CD excluded volume (1410, 1440 Å3) falls in with the lowest values of that in low molecular adducts (1410-1770 Å3). Based on these, the coaxial position of the polymer chain and the cycle molecules in beta-CD-PVDC and in its derivatives was determined. Hydrogen bonds are assumed to be the main ones between the PVDC chain and beta-CD molecules as well as between beta-CD molecules themselves. They link the adduct components to each other with the aid of covalent bond forces. A higher degree of space filling of the PVDC chain in beta-CD adduct canal cavities (0.80) than for the PVDC crystal lattice itself (0.76) is assumed to be the basis of the topology in the adducts.

ISSN:0022-233X    

DOI:10.1080/00222338108058481

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The kinetics of the exchange of potassium ions in a cationexchange resin has been studied. The rate measurements have been made by a potentiometric technique, and both the kinetic and the activation parameters of the reaction were determined. The rate-controlling step, at the beginning of the reaction, has proved to be the diffusion of the K+ions through the film surrounding the resin beads.

ISSN:0022-233X    

DOI:10.1080/00222338108058482

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A study on the gas-phase photolytic oxidative degradation of volatile methyl silicon species has been conducted with ozone O3as a convenient source of photolytic oxygen. Such a study would provide the relative reactivity data which may permit an immediate comparison of environmental persistence of volatile methyl silicon compounds such as octamethylcyclotetrasiloxane (D4), hexamethyldisiloxane, and tetramethyl-silane with n-octane. A reaction vessel was devised to allow convenient generation of ozone, measurement of its concentration, syringe introduction of the compounds, and periodic sampling of gas sample for GC analysis of their disappearance rates on irradiation with a UV source from which light shorter than 290 nm was filtered off. The results on the photolysis of O3and D4revealed that their decomposition is appreciably accelerated in the presence of water. The rate of decomposition of D4increased with increasing initial ozone concentrations. It was found that the plot of log HLD4vs log [O3]0was linear, where the HLD4represents the half lifetime of D4. When the reactions were run at similar molar ratios of [O3]0, the following relative disappearance rates were observed: D4, (Me3Si)2O, n-octane, Me4Si: 3.3, 1.4, 1.0, 0.55.

ISSN:0022-233X    

DOI:10.1080/00222338108058483

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The synthesis of cellulose graft copolymers using condensation reactions to graft onto the cellulose backbone is described. Cellulose acetate (D.S. 2.27) was grafted with MDI and TDI. The cellulose acetate-MDI copolymer was further reacted with hydroxy-terminated poly(butadiene-styrene) copolymer and polyethylene glycol. Grafting was confirmed by Pmr and IR spectroscopy. The copolymers were easily deacetylated with NaOMe. The deacetylated products were readily degraded by cellulysin, faster than cellulose itself.

ISSN:0022-233X    

DOI:10.1080/00222338108058484

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The synthesis of cellulose graft copolymers using a vinyl addition type graft reaction procedure is described. Cellulose acetate (D.S. 2.37) was first mercaptoethylated and then reacted with styrene in the presence of benzoyl peroxide. The degree of grafting was varied. Grafting was confirmed by IR spectroscopy. The copolymers were smoothly deacetylated with NaOMe. The deacetylated products were readily degraded by cellulysin.

ISSN:0022-233X    

DOI:10.1080/00222338108058485

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The graft copolymerization of methyl methacrylate onto silk fibers was investigated in aqueous solution using the V5+−thiourea redox system. The rate of grafting was determined by varying monomer, thiourea, acidity of the medium, temperature, initiator concentration, and reaction medium. The percentage of graft yield increases significantly by increasing the initiator concentration up to 0.01Mand thereafter decreases with a further increase of initiator concentration. The graft yield increases with an increase of thiourea concentration up to 10.0 × 10−4and then decreases with a further increase of thiourea concentration. The effect of increasing the monomer concentration brings about a significant enhancement in the graft yield. A suitable kinetic scheme has been proposed and the rate equation has been evaluated.

ISSN:0022-233X    

DOI:10.1080/00222338108058486

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The graft copolymerization of methyl methacrylate onto silk fibers initiated by the ferric chloride-eysteine redox system has been investigated in aqueous medium. The rate of grafting was calculated by varying the concentrations of monomer, initiator, acidity of the medium, cysteine, and temperature. The percentage of grafting increases with an increase of Fe3+concentration up to 2,5 × 10−3mol/L and thereafter it decreases. The graft yield increases steadily upon increasing the monomer concentration. The graft yield also increases with increasing cysteine concentration up to 0.5 × 10−3mol/L and then decreases. The effect of the perchloric acid concentration, temperature, solvents, and certain neutral salts on graft yield has also been investigated and a suitable reaction scheme has been proposed.

ISSN:0022-233X    

DOI:10.1080/00222338108058487

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The efficiency of the chemical cross-linking of polypropylene was found to be dependent on the peroxide used (dicumyl peroxide, benzoyl peroxide, t-butyl peroxide, and t-butyl peroxy-benzoate). The reason for different cross-linking efficiency of peroxide and enhancement of the cross-linking efficiency of peroxide in the presence of polyfunctional monomer-penta-erythritol tetrallyl ether are discussed.

ISSN:0022-233X    

DOI:10.1080/00222338108058488

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

Poly(L-leucine) and poly(L-phenylalanine) cross-link with either 2,4-toluene diisocyanate or 1,6-hexane diisocyanate but no such cross-linking resulted for poly(γ-benzyl-L-glutamate). The latter polymer cross-links, however, upon transesterification with diols.

ISSN:0022-233X    

DOI:10.1080/00222338108058489

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A sensitive thermal dehvdrochlorination method has been used to determine quantitatively the HCl arising from -CH2C(CH3)2Cl endgroups in polyisobutylenes synthesized by BCb as the co-initiator. Quantitative endgroup analyses provided number-average molecular weights,Mnand functionality,Fn. SelectMndata obtained by this endgroup analysis is in agreement with those obtained by osmometry, GPC, and NMR techniques; indeed,Mn's obtained by this dehydrochlorination technique appears to be more accurate (2-3% error) than conventional methods (∼5-10% error). The rate of HCl loss from -CH2C(CH3)2Cl termini is first order in HCl with an ΔEaof 19.1 kcal/mol in the 170-200°C range. This relatively low activation energy is most likely due to internal strain in the -CH2C(CH3)2CH2C(CH3)2Cl endgroup. These studies quantitatively substantiate earlier conclusions in regard to the mechanism of endgroup formation in BC13 coinitiated isobutylene polymerization.

ISSN:0022-233X    

DOI:10.1080/00222338108058490

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor