摘要:

AbstractThe actual viscosity η of six fractions of poly(2,4,5‐trichlorophenyl methacrylate) (PTCPh) with weight‐average molecular weightM̄w, ranging from 9,11 · 104to 94,8 · 104, was determined in benzene at a number of temperatures from 22 to 60°C. The variation of the pre‐exponential termAand the apparent activation energy of viscous flowQ, with molecular weight and concentration was studied. Moore's equations are valid for PTCPh. The temperature coefficient of the unperturbed dimensions dln 〈r20〉/dTestimated from the intrinsic viscosity data by using the Burchard‐Stockmayer‐Fixman relation, is −3 . 10‐3(from 22 to 40°C) and −0,87 . 10‐3(from 40 to 60°C). These negative values indicate that extended configurations of PTCPh in benzene must be as

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830311

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe present work deals with a general framework of the kinetics and the microstructure (sequence distribution of monomeric units, network parameters…) of resins constituted of vinyl and diene monomers based on the theory of Markov chain propagation. As a matter of example, calculations were applied to the copolymerization of styrene withp‐ andm‐divinylbe

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830312

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractRadical cyclopolymerization ofN‐propyldimethacrylamide (PDMA) was investigated. Kinetic orders of polymerization rate with respect to the monomer and the initiator were 1,0 and 0,5, respectively, at a monomer concentration greater than 1,6 mol/l. Absolute values of rate constants of propagation and termination reactions were determined by the rotating sector method in bulk and in 50% propionitrile solution at 30°C. Poly(PDMA) consists of 5‐membered cyclic repeating units almost exclusively. The rate constants for addition of poly(PDMA) radical to vinyl monomers and those for addition of polymer radicals to PDMA were also evaluated. One the basis of the rate constants obtained, the rate determining step of PDMA propagation was deduced to be the intermolecular addition of the growing radical to PDMA monomer. The growing radical of PDMA, formed by intramolecular addition to the carbon‐carbon double bond of the same molecule, was found to be as reactive as polymer radicals from reasonance stabilized monomers. The 5‐membered ring formation was highly favored by the conformation of PDMA in which coplanarity of the newly formed bond and the semi‐occupied orbital of the new radical center is readily achieved. Relatively low reactivity of poly(PDMA) radical was accounted for by delocalization of the unpaired electron on the coplanar three carbon atoms. Radical addition of a 2‐tertiary thiol to PDMA solely yielded the substituted succinimide. The 5‐membered ring formation in PDMA polymerization and in the addition reaction was ascribable to the favorable confor

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830313

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractFor the free radical oligomerization of styrene monomer in the presence of carbon tetrachloride, a simplified reaction mechanism is proposed from which a simple scheme for predicting monomer conversion and molecular weight distribution is obtained. The kinetic constants other than those of the initiator decomposition step are determined by use of conversion data. In the scheme development, the kinetic constants for chain transfer and propagation steps are considered to be chain length independent, except that for the propagation step, an extra rate constant is considered for the reaction of monomer with radical produced in the transfer reaction with solvent. The mechanism proposed is found to be in reasonable agreement with out experimental data.

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830314

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe kinetics of polymerization of acrylamide, acrylonitrile and methyl methacrylate by the systems cyanoacetic acid/Mn(OCOCH3)3as well as ethyl acetoacetate/Mn(OCOCH3)3were investigated in glacial acetic acid medium in the temperature range of 25–45°C. Oxidation proceeds through intermediate complex formation between reactants. Competitive complexation of the substrates by Mn(II) leads to retadation of the rates by added manganous ions. Primary radicals from the substrate account for the initiation when acrylamide is used as the monomer, but with acrylonitrile and methyl methacrylate secondary radicals formed by the interaction of the 1:1 complex with monomers account for initiation. In presence of the monomers the retardation due to added manganous ions is absent. Termination in all cases is of the mutual type. Rate and equilibrium constants were evaluat

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830315

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe previously deduced four‐parameter equation of state for melts of linear polymers was reduced to a three‐parameter form, consistent with the theorem of corresponding states. The methods of determining the characteristic parameters of the new and the previous equation are given. The characteristic parameters for polystyrene, poly(o‐methylstyrene), poly(vinyl acetate), linear polyethylene, isotactic polypropylene and poly(butyl methacrylate) are calculated, using the experimentalpVTdata from literature. The dependence of the characteristic pressure on the temperature, observed in the case of poly(butyl methacrylate) is explained in terms of bending of the valency angle at the —CH2‐group in the backbone, due to strong steric hindrances in vinylide

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830316

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractComplexation between polyelectrolytes and hydrous inorganic oxides was investigated by turbidity and conductance measurements. Vapor (water and organic) adsorption isotherms on the complex were determined as a function of relative humidity with a gravimetric method. The adsorptivity increases in the order benzene

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830317

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPolymerization of methyl methacrylate initiated by laurates of Fe(III), Co(III) and Mn(III) in benzene medium at 60°C was studied. The polymerization was found to be free radical in nature. The rate of polymerization was proportional to the square of the concentration of the monomer and inversely proportional to the concentration of the solvent. The initiator exponent was found to be 0,23. The rate parameters for the system were evaluated. The reactivity of the different metal laurates was compared. A kinetic scheme is proposed in the light of the experimental results involving initiation of the polymerization by a monomer‐initiator complex and termination by a initiator‐solvent com

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830318

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractNative DNA (M̄w: 5 · 106and 2 · 107) was irradiated at a concentration of 0,l g/l in Ar‐ or N2O‐saturated solutions. Emphasis was given to reactions induced by OH radicals. The solutions were irradiated with single 16MeV electron pulses (100 ns pulse length) in conjunction with time‐resolved Rayleigh light scattering measurements. It turned out that crosslinking and double strand breakage (dsb) can be clearly separated, the former proceeding faster than the latter. The extent to which the two processes—which counteract with respect to changes of the light scattering intensity (LSI)—occur, depends strongly on the ionic strength of the solution. At [NaClO4]>10−1mol/l crosslinking is the predominant process, which is assumed to be caused by the fact thathcrit, the critical length for the accomplishment of dsb, is strongly reduced. Thus, up to several hundred single strand breaks (ssb) per chain can remian ineffective with respect to the generation of dsb at high ionic strength. Crosslinking can occur both as an inter‐ and an intramolecular process. As inferred from light scattering measurements singlestranded DNA did not crosslink at a concentration of 0,l g/l and at low ionic strength, but underwent main‐chain rupture. The rate of LSI decrease is correlated to the rate of fragment diffusion. The half‐life time of the LSI decrease depends on M̄was τ½∝︁ M̄ w,00,6. It was concluded that the lifetime of the species responsible fo

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830319

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe preferential solvation of poly(methacrylic acid) and poly(sodium methacrylate) in waterdioxane mixtures was investigated by means of specific refractive index increment measurements on dialysed and undialysed solutions. The correlation with the solvent‐induced conformational transition of poly(methacrylic acid) was also studied. Potentiometric titrations indicate that this transition occurs at around 25–30 vol.‐% of dioxane. Comparison with previous results on poly(acrylic acid) and poly(sodium acrylate) in the same solvent system and on poly(methacrylic acid) in water‐2‐chloroethanol mixtures, shows differences in the mode of solvation of the compact conformation. It is suggested that this may be dependent on the existence of water‐organic solvent specific interactions such as the formation of a water‐dioxane hydrogen

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830320

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY