摘要:

AbstractThe molecular weight dependence of the Lower Critical Solution Temperature in polymer solutions has been derived using the Prigogine smoothed potential cell model. Satisfactory agreement is obtained with experimental results for a number of systems. It is found that the new structural term (or equation of state term) in χ introduced by the Prigogine theory accounts for the LCST. Any difference in chemical nature between the polymer and solvent molecules may be largely ignored. The structural term also has an effect on the molecular weight dependence of the familiar Upper Critical Solution Temperature. It is predicted that fractionation of a polymer could be improved by choosing a solvent for which the UCST and LCST were separated by only a small temperature interval. Fractionation at the LCST should not be more efficient than at the UCST

ISSN:0449-2994    

DOI:10.1002/polc.5070300103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractIn a binary solvent mixture, the χ1 2interaction parameter has a marked influence upon the intrinsic viscosity of a polymer. If χ1 2is positive, the [χ] value is higher than the weighted average of the viscosities measured in the pure constituents. When the latter are non‐solvents of the polymer, and the mixture dissolves it, the so‐called cosolvency‐effect requires a positive value of χ1 2. If χ1 2is negative, the [χ] value is found lower than the average of the viscosities measured in the pure constituents. Demixtion can even occur when in a given composition range the mixture of two good solvents behave like a precipitant (χ1 2<0). Athermal mixtures (χ1 2= 0) exhibit no such effect, and behave like a pure solvent.To determine the unperturbed dimensions of a polymer coil in various binary solvent media, the Stockmayer‐Fixman extrapolation was used. It is known that for a given polymer the sameKχvalue is found in any pure solvent. In binary mixtures theKχvalues are found higher or lower than this unique value, depending upon the sign of χ1 2. These qualitative results remains valid as long as selective adsorption of the better solvent on the chain remains low. If this is not the case, account has to be taken of the fact that composition inside the coil is not identical with the average composition of the mixture.A pure solvent in which molecules have a tendency to associate behaves like a solvent mixture in which χ1 2is negative: theKθvalue is found lower than the uniqueKθvalue for this polymer in al

ISSN:0449-2994    

DOI:10.1002/polc.5070300104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

ISSN:0449-2994    

DOI:10.1002/polc.5070300105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

ISSN:0449-2994    

DOI:10.1002/polc.5070300106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

ISSN:0449-2994    

DOI:10.1002/polc.5070300107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractPolystyrene has been found to be completely soluble in the following binary mixture of non‐solvents,viz. nitrobenzene and acetone, heptane and acetone, cyclohexane and acetone, nitrobenzene and diethyl oxalate, hexane and diethyl oxalate, cyclohexane and diethyl oxalate. Polymethyl methacrylate has similarly been found to be soluble in carbon tetrachloride and methanol, and in carbon tetrachloride and ethanol. These two polymers have been studied viscometrically, osmometrically and with respect to light scattering property. An optimum composition with a minimum in osmotic μvalue and viscometric Huggins constant, a maximum in [η]‐value and a maximum in dissymmetry coefficient has been found to exist. The above observations are considered to indicate that the composition showing maximum solvent power is a true optimum composition and the dissolved unit is laterally more extended in this optimum composition than at any other composition of the two non‐solvents. Five samples of polymers have been studied in a number of ø‐mixtures near room temperature with a view to obtain theKøvalues of Flory‐Fox equation, [η] ø =KoM̄v0.5. It has been found thatKøvalues vary widely with the chemical nature of the theta mixture indicating solvent dependency of unperturbed

ISSN:0449-2994    

DOI:10.1002/polc.5070300108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractOn détermine le moment électrique permanent μ et le temps de relaxation d'échantillons de poly‐L‐glutamate de benzyle et de poly‐DL‐phénylalanine dans l'acide dichloracétique (ADC) et les mélanges ADC‐heptane ou ADC‐chloroforme, solvants où ces polypeptides sont en chaǐne. L'élèment constitutif de ces polymères a une composante du moment dipolaire le long de la chaǐne et toujours dirigée vers la měme extrémité. Dans les bons solvants, on trouve que μ2/Maugmente avecM, tandis que dans les mélanges de solvants qui se comportent comme un solvant théta, aucune variation de μ2/MavecMn'a été observée. Les variations du temps de relaxation en fonction deMont également été déterminées dans de bons et mauvais solvants et comparées aux calculs de Zimm. On montre ensuite comment la transition chaǐne‐hélice du PLGB dans un mélange du solvants peut ětre mise en évidence par l'étude de la variation de la

ISSN:0449-2994    

DOI:10.1002/polc.5070300109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe frictional coefficients. [f] of a wide range of poly‐α‐methylstyrene samples ranging in molecular weight from dimer to polymers ofM∼ 106have been measured in a good solvent (toluene) and under θ conditions (cyclohexane, 37°C). All products were prepared anionically, and the very low molecular weight samples were initiated with phenyl‐isopropyl potassium to ensure that the end‐groups were not significantly different from the polymer chain. [f] was measured using both diffusion and sedimentation techniques. At molecular weights below ∼ 104, [f] is independent of solvent and proportional toM0.5to quite low molecular weight. Divergences only occur at the very lowest part of the range. AboveM∼ 104, [f] continues to be proportional toM0.5in cyclohexane as expected, but the values in toluene become greater because of greater chain expansion in the better solvent. The results are discussed in terms of current theories of conformations of polymers in solution and its effect on

ISSN:0449-2994    

DOI:10.1002/polc.5070300110

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

摘要:

AbstractThe first study by the Monte‐Carlo method of the dynamical comportment of macromolecular chains in solution was made by Verdier and Stockmayer. We have adapted the method proposed by these authors to the case of a chain built in a tetrahedral lattice with volume‐excluded‐condition, for analyzing the brownian motion of a macromolecular in solution. This is done by submitting the chain to a very great number of elementary motions of 1, 2, 3 or 4

ISSN:0449-2994    

DOI:10.1002/polc.5070300111

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY

ISSN:0449-2994    

DOI:10.1002/polc.5070300112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1970

数据来源: WILEY