摘要:

AbstractPrevious theories valid for polymer chains with large loops protruding into the solvent are developed. Interaction in various layers parallel to the interface is calculated according to the Flory‐Huggins theory. Excluded volume effects are shown to be so small that they can be neglected. The adsorption isotherm is expressed in two parameters: one for the partition function for adsorbed segments and the other one for the stiffness of the chains. For adsorption from good solvents, the fraction of segments in the surface layer is large and the loops are small. For adsorption from theta‐solvents, the fraction of segments in the surface layer is small and the loops are large. The trends are in agreement with those experimentally observed, but the observed layer thickness is larger than the theoretically deduced upper li

ISSN:0449-2994    

DOI:10.1002/polc.5070340103

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

年代:1971

数据来源: WILEY

摘要:

AbstractDensity, heat of fusion and melting temperature data of annealed polyethylene single crystals suggest the existence of a temperature‐dependent pseudo‐amorphous surface layer which contains chain folds and free chain ends. In the ideal two‐phase model, one assumes two such amorphous layers of thickness ℓ/2 each on the two (001) surfaces of the crystalline core of thickness D = L ‐ℓ, where L is the total thickness of the single crystal. The thickness of such a layer was calculated under the assumption of random length loops and cilia (free chain ends) for the case of adjacent reentry and of a Maxwellian distribution of loop width. The excess energy requirement of the shortest loops with the high concentration of gauche conformations favors longer loops and hence increases the surface layer thickness. The reduction of entropy by the restrictions imposed by finite loop width and the availability of a half space only acts in the opposite direction. The calculated thickness depends on the true supercooling ΔT = Tm° ‐ T if L is kept constant and on relative supercooling ΔTrel= Tm‐T, where Tmis the actual melting point of the crystal, if the crystal core thickness D is kept constant. A qualitative agreement between theory and experiment on this basis seems possible by proper consideration of the contribution

ISSN:0449-2994    

DOI:10.1002/polc.5070340104

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

年代:1971

数据来源: WILEY

摘要:

AbstractWe propose an equation, based on “reciprocal” mean and force additivity, for calculating the interfacial tension between polymers or between a polymer and an ordinary liquid:\documentclass{article}\pagestyle{empty}\begin{document}$$ \gamma _{12} = \gamma _1 + \gamma _2 - \frac{{4\gamma _1 ^{\rm d} \gamma _2 ^{\rm d}}}{{\gamma _1 ^{\rm d} + \gamma _2 ^{\rm d}}} - \frac{{4\gamma _1 ^{\rm p} \gamma _2 ^{\rm p}}}{{\gamma _1 ^{\rm p} + \gamma _2 ^{\rm p}}} $$\end{document}where γ12is the interfacial tension; γithe surface tension; γ idand γ idthe dispersion and polar components of γi, respectively. This equation is shown to predict accurately the interfacial tension between polymers or between a polymer and an ordinary liquid. Fowkes' equation or Fowkes' equation with a geometric‐mean polar term 2(γiPγ2p)1/2is not applicable to polarlpolar systems. The interfacial tension arises mainly from disparity in the polarities of the two phases. The above equation can also be used to calculate the surface tension and polarity of polymers or organic solids from co

ISSN:0449-2994    

DOI:10.1002/polc.5070340105

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

年代:1971

数据来源: WILEY

摘要:

AbstractPrincen's modification of Vonnegut's rotating drop procedure for measuring inter‐facial tension between low viscosity liquids has been adapted for use with pairs of liquid polymers with viscosities up to 5000 poise. Extrapolation to infinite time of results obtained with 10–20 min of rotation provided steady state data as indicated by its corre‐spondence with results reported from other techniques. An adaptation of this procedure was also found useful for determining surface tension values of molten polymers at temperatures up to 290°C. Reductions of 60–70% in interfacial tension between viscous samples of a polydimethylsiloxane and a copolyether were accomplished by addition of 1–2% of amphi‐pathic or polar compounds such as polydimethylsiloxane‐polyoxyethylene copolymers and carboxyl‐substituted polydimethylsiloxanes. A linear reduction in interfacial tension with a logarithmic increase of additive concent

ISSN:0449-2994    

DOI:10.1002/polc.5070340106

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe surface tension of mixtures of poly(dimethylsiloxane) and poly(isobutylene) fluids with their low molecular weight oligomers have been measured. These data, as well as those for n‐alkane mixtures from the literature, are fitted well by lattice‐theory expressions for the surface tension of polymer solutions, and do not show a simple dependence on the average molecular weight in the mixture. We conclude that the molecular weight depend‐ence we have previously observed for the surface tension of polymer fluids is only an approximation. The results also suggest that the lattice‐model theory may have broader applicability than the model from which it was developed woul

ISSN:0449-2994    

DOI:10.1002/polc.5070340107

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe monomolecular film of monooctadecyl phosphate (mOP) spread at an air‐water interface was employed to elucidate the nature of the interaction between peptide hormones and the cell membrane. First, the effect of peptide hormones on the uptake of calcium ion (Ca++) by the monolayer was examined from the emission of45Ca radioactivity through the monolayer. Insulin inhibited the initial uptake of Ca++and facilitated the release of adsorbed Ca++. These effects were partially or completely lost with insulin analogs. Vasopressin and oxytocin inhibited the adsorption of Ca++. Vasopressin facilitated Ca++release, whereas oxytocin did not. Thyrocalcitonin profoundly inhibited Ca++uptake, but facilitated only slightly the release of Ca++. Parathyroid hormone had negligible effect. The molecular basis and the biological significance of these results are discussed. Secondly, the effect of peptide hormones on the transport of water through the mOP monolayer was examined. Ca++increased the specific resistance to evaporation of water. In the presence of Ca++, insulin and vasopressin lowered the resistance to evaporation (or increased the trans‐port of water). This effect of the hormones could not be accounted for entirely by the inhibition of Ca++upt

ISSN:0449-2994    

DOI:10.1002/polc.5070340108

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

年代:1971

数据来源: WILEY

摘要:

AbstractInfrared studies of the amide I band of transferred films of β‐lactoglobulin‐B spread on 0.5 M KC1 have been obtained via the multiple internal reflection (MIR) technique. The spectra indicate that the conformations of the films change with surface pressure. The data are consistent with a denatured molecule as the predominant species at high area per molecule and a species whose secondary structure is similar to that of the native molecule at high degree of compression. The transition may be reversed by re‐expansion of the film after compression. Approximately equal amounts of native‐type and denatured type spectral components are found at 6 dynes/cm at room tem

ISSN:0449-2994    

DOI:10.1002/polc.5070340109

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

年代:1971

数据来源: WILEY

摘要:

AbstractRecently, evidence has been obtained that the monolayers of a number of synthetic polypeptides are in the α‐helical conformation at the air‐water interface. This hypothesis has been based on measurements of deuterium exchange rates and examination of collapsed films by infrared spectroscopy.In this paper, the influence of the interface is studied with a method of the surface chemistry: the surface potential. The modification of the properties of the ionized groups with the macromolecular conformation was more particulary investigated in the case of poly‐L‐glutamic acid. Orientation of the molecules in the monolayers is imposed by the nature of the interface (air‐water, cyclohexane‐water). The theories of the ionic double layer (Gouy model, Donnan equilibrium) allow to calculate α, the degree of ionization of the film. The results obtained demonstrate that, at the cyclohexane‐water interface, the accessibility to the ionized groups is more difficult than at the air‐water interface. The variation of α with the PH of the substrate is used to calculate an intrinsic dissociation constant K s0of the monomer of the spread molecules. The values are similar to that

ISSN:0449-2994    

DOI:10.1002/polc.5070340110

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

年代:1971

数据来源: WILEY

摘要:

AbstractMolecular monolayers of a range of synthetic polypeptides spread at the air‐water interface have been investigated. Measurements of the surface pressure and surface potential are correlated with the chemical composition of the side chains. All the polymers are believed to be in the α‐helical conformation at the air‐water interface and the surface potential is accounted for principally by the interaction of the peptide groups with the underlying water; if however, there are ester groups in the side chains, an additional side chain‐water interaction is evident. The infrared absorption spectrum of water and alcohols adsorbed from the vapor on thick orientated specimens in the α‐helical conformation prepared from collapsed monolayers has also been investigated. The OH absorption of water, methanol and ethanol is dichroic and shows evidence of interactions similar to those required to account for the surfac

ISSN:0449-2994    

DOI:10.1002/polc.5070340111

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

年代:1971

数据来源: WILEY

摘要:

AbstractA series of poly [methyl(n‐alkyl)siloxanes] were studied as insoluble monomolecular films on the following organic substrates: tricresyl phosphate, propylene carbonate, diethyl phthalate, and a highly chlorinated polyphenyl (Aroclor 1242). The siloxanes were discovered to form stable, insoluble, reproducible monomolecular films at each organic liquid/air interface. Film pressure (F) vs. area/molecule (A) isotherms were determined in each instance and were compared with previously determined F‐vs.‐A isotherms for polydi‐methylsiloxanes on the same organic substrates as well as on water. By combining the film balance data with molecular dimensions calculated from ball models, it was possible to make several tentative conclusions regarding the conformation of the adsorbed siloxane molecules as a function of film pressure, n‐alkyl chain length and substrate composition. The F‐vs.‐A curves for the poly(methylethylsiloxane) and polydimethylsiloxane films were consistent with the assumption that they assume a helical configuration when compressed at organic liquid/air interfaces; however, there is little evidence to indicate whether the polymer chains become fully extended at higher areas/molecule or remain in a somewhat coiled

ISSN:0449-2994    

DOI:10.1002/polc.5070340112

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

年代:1971

数据来源: WILEY