摘要:

We show that the copolymerization of citraconic anhydride and vinyl acetate is an alternating one. The two monomers form a charge transfer complex, and we propose a new strategy to determine the value of the velocity constants β1= KAC/KADand β2= KDC/KDAinvolving the acceptor A, the donor D, and their charge transfer complex C. We obtained β1= 9.9 and β2= 3.6. The complex exhibits a greater reactivity than the monomer in the propagation reactions.

ISSN:0022-233X    

DOI:10.1080/00222338508063349

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The poly-(2-methoxycyanurate) of l, l′-bis-(4-hydroxyphenyl)-cyclohexane (PMCBC) was synthesized by the interfacial poly-condensation technique. The polymer was fractionated by preparative gel permeation chromatography (GPC). The fractions were characterized by viscometry, osmometry, and GPC techniques. The viscosity-molecular weight relationship was established in pure solvent and in different binary solvent mixtures. The unperturbed dimensions, (⟨R2⟩0/M)1/2, and the solvent-polymer interaction parameter, B, were computed by applying the two-parameter theories of the excluded-volume effect.

ISSN:0022-233X    

DOI:10.1080/00222338508063350

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Elementary combinatorial analysis was used to derive formulas for the number of arrangements of a random linear copolymer that contained none of a specified sequence, AB, ABB, BBA, ABA, or ABC. This enabled the probabilities of finding none, or at least one, of the specified sequence to be calculated.

ISSN:0022-233X    

DOI:10.1080/00222338508063351

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The polychelates of bivalent metal ions such as copper, nickel, cobalt, manganese, and zinc have been synthesized from polymeric ligands derived from 4,4′ -dihydroxy-3,3′ -diacetyl biphenyl and 4,4′-diamino diphenyl methane. Elemental, magnetic susceptibility, visible and IR spectra, and thermal properties have been studied. The analytical data suggest the general formula (ML)nfor the polychelates. The polychelates are quite stable but insoluble in common organic solvents.

ISSN:0022-233X    

DOI:10.1080/00222338508063352

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Some combinations of N-hydroxysuccinimide (NHS) and acetyl-acetonato metal chelates were found to induce radical polymerization. A kinetic study on the polymerization of methyl methacrylate (MMA) was performed by using as initiator the NHS/trisacetyl-acetonatomanganese(III) (Mn(acac)3) system, which can initiate the polymerization effectively even at room temperature. The overall activation energy of polymerization was very low (9.1 kcal/mol). The polymerization rate (Rp) was expressed by

ISSN:0022-233X    

DOI:10.1080/00222338508063353

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The effect of water vapor pressure on the molecular weight of molten poly (ethylene terephthalate) has been followed by measurement of the changes which occur in the intrinsic viscosity and the end-group concentrations upon hydrolysis. It was found that phosphoric acid is highly effective as a stabilizer; the hydrolysis rate constant (Kh) decreasing from 7.6 × 10−7mol−1s−1for nonstabilized to 2.5 × 10−7mol−1s−1for the stabilized polyester at 290°C and water vapor pressure of 20 mmHg.

ISSN:0022-233X    

DOI:10.1080/00222338508063354

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The use of carboxypeptidase for sequence determination is attractive because of its technical simplicity. In chemical methods all molecules of a peptide are made to go through a degradation cycle before a new cycle is started. In the enzymatic degradation of a protein, the order of the amino acid residues is not necessarily determined in a stepwise fashion but rather from the rate at which the amino acids appear in the digest, i.e., an amino acid appearing faster than another presumably precedes it in the sequence. Under favorable circumstances the rate of appearance of the amino acids released during digestion give sufficient evidence for the C-terminal sequence to be deduced. The present work pertains to a study on the use of immobilized carboxypeptidase A columns for sequential analyses.

ISSN:0022-233X    

DOI:10.1080/00222338508063355

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The classical copolymerization rate equation does not describe the copolymerization rate in the styrene-butyl-acrylate-azoiso-butyronitrile-benzene-50°C system appropriately. The cross-termination coefficient (Π), calculated according to the classical rate equation, shows a strong monomer and solvent concentration dependence. The experimental results cannot be interpreted by the diffusion theory, penultimate effect, or the theory of charge transfer complexes. However, Π was found to be constant over the whole concentration range by the hot radical theory. Our kinetic data were consistently described by this theory, and its 13 parameters, characteristic of the copolymerization, were determined.

ISSN:0022-233X    

DOI:10.1080/00222338508063356

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Several methods based on the Huggins equation are available for studying the behavior of linear flexible high polymers in the Newtonian region of concentrated solutions. The work of Simha and Zakin has attracted our attention to further investigation since it suffers from limitations in the type of solvent and the molecular weight range of the polymer suggested for study. It was observed that a suitable modification of the Huggins equation would widen the scope of the original method. An alternative method for determining the incipient concentration c0where the intermolecular attraction and the repulsion just balance each other, is also suggested.

ISSN:0022-233X    

DOI:10.1080/00222338508063357

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The synthesis of atactic poly(propylene-g-ethyl acrylates) of [Mbar]n∼ 3000–5000 has been accomplished with 80–90% incorporation of the backbone in the graft copolymer. The principle involves free radical initiation of ethyl acrylate polymerization with benzoyl peroxide via chain transfer. At low conversions (up to ∼15%), massive homopolymerization took place and the initial rates of both homo- and graft copolymerizations were indistinguishable even with 1% initiator based on monomer. Grafting occurred at higher conversions and the [Mbar]nof the grafted product increased with increasing initiator concentration for almost similar conversion data. The isothermal stability of the graft copolymer was far superior to that of atactic polypropylene. The initial decomposition temperature of the graft copolymers increased with increasing initiator amount used for grafting. It is proposed that the number of branches of poly (ethyl acrylate) increased, following the abstraction of an increasing number of tertiary hydrogen atoms from the backbone.

ISSN:0022-233X    

DOI:10.1080/00222338508063358

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor