摘要:

Kinetics of polymerization of acrylonitrile initiated by the redox system V5+ascorbic acid were investigated in aqueous sulfuric acid in the temperature range of 35–50°C, and the rates of polymerization, of V5+/disappearance, etc. were measured. From the result it was concluded that the polymerization reaction is initiated by an organic free radical arising from the V5+- ascorbic acid complex formation followed by subsequent decomposition and terminated by V5+ions. A suitable kinetic scheme was proposed and the various rate parameters were evaluated.

ISSN:0022-233X    

DOI:10.1080/00222338208074403

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Methyl-4-vinylphenylsulfoxide (1) was prepared by the selective oxidation of 4-methylthiostyrene with sodium metaperiodate in 87% yield. This monomer was readily homopolymerized in DMSO by AIBN at 60°C. The polymer obtained is soluble in ethanol, chloroform, DMSO, and DMF, but insoluble in water, benzene, and petroleum ether. The inherent viscosity of this polymer was 0.33 dL/g in DMSO. This sulfoxide monomer (1) was copolymerized with styrene, methyl methacrylate, acrylo-nitrile, and acrylamide under radical conditions. From the copolymerization with styrene, copolymerization parameters were obtained as follows; r1= 0.56, rSt, = 0.26, and Q1= 1.19, e1= 0.58. Similarly, methyl-4-vinylbenzylsulfoxide (2) was prepared, and the polymerizability of (2) was also investigated.

ISSN:0022-233X    

DOI:10.1080/00222338208074404

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

4-Bromosalicylic acid (BS) was condensed with various proportions of formaldehyde using different acid catalysts. The polymer samples have been characterized by IR spectral studies, by their number-average molecular weight (Mn), and by TGA. Viscosity measurements of selected polymer samples in DMF showed that their solutions exhibited polyelectrolyte behavior. The intrinsic viscosity [η] of the polymer samples were measured in 80:20 (v/v) DMF/water containing 1% KBr, a medium in which the polymers exhibited normal behavior. Metal chelates of one polymer sample are characterized. Ion-exchanging properties of the same sample are studied by application of the batch equilibrium method

ISSN:0022-233X    

DOI:10.1080/00222338208074405

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Equilibrium studies of mixed UO2(II)-complexes containing 2,2′-bipyridyl (Bipy) or 1,10-phenanthroline (Phen) as the first ligand and N,N′-dimercapto acetyl ethylene diamine (DMAED) or N,N′-dimercapto propionyl ethylene diamine (DMPED) as the second ligand in equimolar ratio were made in aqueous medium at 30 ± 1°C and at constant ionic strength (0.1M, NaClO4) in an inert atmosphere. Evidence was found for the hydrolysis of the complex containing metal and the first ligand at a pH before the second ligand could interact with the binary species. The conditional formation constants for the hydrolyzed binary complexes were evaluated on the basis of hypothetical (1:1) stable species and applying the Irving-Rossotti pH titration technique. All the mixed ligand complexes are shown to-have formed in a stepwise manner according to the equilibrium

ISSN:0022-233X    

DOI:10.1080/00222338208074406

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The rate of copolymerization of vinyl chloride (VC) with sulfur dioxide and the composition of the poly (vinyl chloride sulfone) formed have been measured for comonomer liquid mixtures with XVC= 0.1 to 1.0 and over the temperature range -95 to +46°C.

ISSN:0022-233X    

DOI:10.1080/00222338208074407

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The mechanism of copolymerization of vinyl chloride (V) with sulfur dioxide (S) to form a variable composition polysulfone with average V:S molar ration≥ 1 is examined. The copolymerization deviates from Lewis-Mayo behavior above -78°C. Alternative models for propagation involving (1) penultimate and pen-penultimate unit effects, (2) complex participation, and (3) depropagation are considered quantitatively by comparison of calculated and experimental copolymer/comonomer composition relationships and comonomer sequence distributions. Our theoretical modeling of the copolymerization shows that it is difficult to discriminate convincingly between alternative mechanisms. The penultimate and pen-penultimate effect models can account for the copolymer compositions, but not for the dilution effects which were observed provided the diluent is truly inert. The complex participation model can account for experimental behavior from -78 to -18°C by the assumption of addition of SV complexes, but it becomes rapidly less satisfactory at higher temperatures. Depropagation is the only model which can account for the compositions and dilution effects above 0°C. Progressive depropagation, with increasing temperature, of chains ending in the triad sequences ∼SVS*, ∼VVS*, and ∼VSV* can explain the observed behavior over the entire comonomer composition and temperature range, but involvement of comonomer complexes in the propagation reactions is highly likely below 0°C.

ISSN:0022-233X    

DOI:10.1080/00222338208074408

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

In this paper are presented the static and dynamic mechanical investigation of chemically cross-linked low density polyethylene (XLPE) prepared in our laboratory. This polymer has been tested mechanically at different frequencies, amplitudes, and temperatures as a function of cross-link density which is indicated to some extent by the amount of peroxide used in the cross-linking. The main findings can be described as follows: mechanical damping in XLPE at the α-relaxation point as a function of peroxide concentration is different for shear and compression modes of deformation. Moreover, the dynamic investigation at very small amplitudes indicated two relatively rigid structures. One structure at low concentration of peroxide is attributed to excessive crystallinity; the other one at the high peroxide concentration is probably due to the very regular and perfect polyethylene network. These two interesting structures are not detected by dynamical testing with large amplitudes. As far as Young's modulus as a function of peroxide concentration is concerned, we conclude that in this polymer this factor does not depend on the crystallinity but on changes of the so-called hard amorphous phase. These findings are consistent with our previous structural investigation.

ISSN:0022-233X    

DOI:10.1080/00222338208074409

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The NMR spectra of the soluble portion of oxidized polyisoprene popcorn polymer has been examined. No single structure can be assigned to the oxidized polymer that is attributable to any particular oxidation mechanism. A 30-h oxidized sample showed a double bond content of approximately 40% cis, 57% trans, and 3% 3,4-addition. There was a very large increase in the content oforandunits as the oxidation time was increased from 30 to 60 h. The presence of, and the large increase in the content ofunits, none of which were observed for nonpopcorn polyisoprenes, can probably be attributed to the increased importance of R radical reactions in the oxidation of the highly cross-linked popcorn polymer structures.

ISSN:0022-233X    

DOI:10.1080/00222338208074410

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The anionic copolymerizations of acrolein (AL) with methyl vinyl ketone (MVK) and acrylamide (AAm) in the presence of imidazole (Im) as an initiator have been studied in tetrahydrofuran at 0°C. The AL-MVK copolymers were found to be composed of vinyl polymer with one Im group attached and having an aldehyde and a carbonyl side chain. The monomer reactivity ratio was determined from a Fineman-Ross plot as r1= 2.02 and r2= 0.06. On the other hand, the AL-AAm copolymer were found to be composed of polymer units of 1,2 and 1,4 addition polymerization of AAm. These observations might be explained by the intermolecular hydrogen transfer mechanism of AAm. The polymerization mechanisms were discussed on the basis of these copolymerization results.

ISSN:0022-233X    

DOI:10.1080/00222338208074411

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Aqueous polymerization of acryionitriie initiated by the Ce(IV)-glycine redox pair was studied at 35°C under nitrogen. The rate of polymerization, Rp, was found to be approximately proportional to the square of the monomer concentration within the range of 0.140s–1.268M. R was also found to increase with glycine concentration in the interval 0.1 to 0.4Mand decrease with cerie ion concentration. The activation energy was estimated to be 25.8 kcal/mol. A suitable kinetic scheme was proposed and explained in the light of these experimental findings. The end-group in the polymer was characterized by IR spectra, and the average molecular weight of the polymer was found to be 84,100.

ISSN:0022-233X    

DOI:10.1080/00222338208074412

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor