摘要:

AbstractPoly‐n‐hexyl isocyanate, prepared according to the method of Shashoua, was fractionated by a coacervation technique. Light scattering and osmometric measurements show that the molecules are enormously extended in solution and can be described in terms of the Porod‐Kratky worm‐like model.Dilute solution viscosity measurements were carried out in a series of solvents and solvent/nonsolvent theta mixtures. Mark‐Houwink constants are reported in which the exponent is very high (a>1) for both pure solvents and theta mixtures. In nonpolar solvents the polymer molecules are too stiff to respond to long‐range thermodynamic forces. The chains relax somewhat in chloroform and on the addition of trifluoroacetic acid due to a change in the effect of short‐range forces. [η] decreases with increasing temperature indicating that the more compact conformations of the molecules have higher energy states than the more

ISSN:0360-8905    

DOI:10.1002/polc.5070420304

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

年代:1973

数据来源: WILEY

摘要:

AbstractA growing battery of methods has become available in recent years for characterization at a molecular level of natural and synthetic polymers. Several methods are now available with automatic or semi‐automatic operation, suitable for routine or on‐line use and are so used in the polymer industry. The methods for characterization are critically reviewed, emphasizing methods now suitable for routine use in the laboratory or in industry, i.e., infrared spectroscopy, viscometry, osmometry, and gel chromatogra

ISSN:0360-8905    

DOI:10.1002/polc.5070420305

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe radical bulk copolymerization of styrene with acrolein, methacrolein, and α‐ethyl‐acrolein is studied and monomer reactivity ratios are determined. Employing the dilatometric method the overall rate of polymerization is measured and discussed with respect to the special structure of copolymers. Quantitative IR spectroscopy is used to elucidate the structure of copolymers, and the absorption behavior of copolymers is compared with the statistical theory on sequence length distribu

ISSN:0360-8905    

DOI:10.1002/polc.5070420306

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

年代:1973

数据来源: WILEY

摘要:

AbstractMonomolecular films of various polypeptides spread at the air‐water interface have been investigated. The conformation in the solid state (e.g.,a‐helical or β‐structure) was known for all the polymers studied. In the surface pressure‐area isotherms thea‐helical polymers gave a distinct flat plateau, whereas the β‐form polymers showed only an inflexion. A correlation between the collapse pressure and the stability in solution for β‐form polymers was found, while no similar relationship was observed for thea‐helical polymers. Surface entropy and enthalpy were determined for each polymer and these results indicated that the polypeptides retained the same conformation in the monolayer as in the solid state, i.e.,a‐helical or β‐structure. Fora‐form polymers a correlation exists between the intermolecular forces in solution and the cohesive forces at the interface. The lack of such a correlation fora‐helical polypeptides thus provides a means of determining the conformation of polypeptides an

ISSN:0360-8905    

DOI:10.1002/polc.5070420307

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

年代:1973

数据来源: WILEY

摘要:

AbstractThere occurs a transition from the local to the continuum viscoelasticity of polymer solutions at the critical concentration, and this affects the change of the form of the concentration dependence of all the characteristics of the viscoelasticity of the solution. For polymers of different molecular weight, the concentration dependences of their viscoelastic properties over the entire range of concentrations are determined by the volume filling of the system.

ISSN:0360-8905    

DOI:10.1002/polc.5070420308

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

年代:1973

数据来源: WILEY

ISSN:0360-8905    

DOI:10.1002/polc.5070420309

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

年代:1973

数据来源: WILEY

摘要:

AbstractIn an electric field, the optical rotation of a solution or suspension of helical molecules may be expected to change. Such changes are reported herein for solutions of poly (benzyl‐L‐glutamate) (PBLG) in ethylene dichloride using pulsed electric fields. These measurements enabled the molecular geometry to be evaluated (through the determination of a rotary diffusion constant) simultaneously with the determination of the molecular optical rotation components along the principal molecular axes. Fields were applied parallel to the light beam. Very dilute solutions were studied owing to the use of a stable laser as the light source plus the introduction of a special multiple cell in which the optical path length could be increased while maintaining the field strength. A dilute solution (0.1%) of PBLG gave rotation data in agreement with previously published data. In addition, the helical length and molecular weight were determined from the relaxation effect. Studies on concentrated solutions indicated the presence of aggregation. This highlights the need for caution in improving the observable optical rotation simply by increasing the solution concentration. The apparatus is described in outline and the advantages of this novel transieat method are lis

ISSN:0360-8905    

DOI:10.1002/polc.5070420310

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

年代:1973

数据来源: WILEY

摘要:

AbstractUsing the Rayleigh‐Gans approximation and expressions for the mean amplitudes (Evv,…,EHv) induced in rigid anisotropic particles which are arbitrarily oriented, one can calculate the four “components” of the light scattered in an arbitrary direction of space. Likewise, using these relations, the turbidity and the “conservative dichroism” of suspensions of anisotropic particles, partially of fully oriented, are studied, and in any case are

ISSN:0360-8905    

DOI:10.1002/polc.5070420311

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe rheological behavior of aqueous solutions of ten acrylic acid and acrylamide copolymers was studied. The mole fraction of acrylic acid in the copolymer ranged from 0.042 to 0.443. Fifteen aqueous solutions for each copolymer were prepared by including all combinations for five values of the degree of neutralization and for three solution concentrations. All other parameters being constant, solution viscosity increases with the degree of neutralization of carboxylic groups in a copolymer. We introduced the expression (ηn–/(η0n), where ηn and η0 are the viscosities of solution at the degree of neutralizationnand 0, respectively, and called it the neutralization viscosity number. It has been found that the limiting neutralization viscosity number forn= 0 is a linear function of the acrylic acid mole fraction in the copolymer with acrylamide and that it is independent of the copolymer molecular weight and solution concentr

ISSN:0360-8905    

DOI:10.1002/polc.5070420312

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

年代:1973

数据来源: WILEY

摘要:

AbstractThermal agitation in liquids consists of high‐frequency elastic waves. Thermal conductivity being a measure of how easily these waves drift down a gradient of temperature can be expressed as a function of the speed of sound in the liquid. The proposed expression agrees with experimental results.More important is the consideration that energy propagating in the form of waves entails propagation of mechanical momentum, the flux of momentum being equal to the flux of energy divided by the velocity of wave propagation. This momentum transported by the waves can be transferred to the bulk of the liquid, thereby contributing to viscosity.Another consequency of the propagation of momentum connected with thermal waves is that whenever heat flows within a solution, radiation pressures are developed, which make the disperse particles migrate along the temperature gradient. This is the physical explanation of thermal diffusion. The analytical expressions which are derived allow us to develop a new method of characterization of polymers and of macromolecules of biological origin. Furthermore, the measurable forces produced by the flow of heat on macroscopic blocks of polymeric materials, suspended by appropriate means within a liquid, show a dependence on the state of the polymeric material and on its thermal and mechanical histor

ISSN:0360-8905    

DOI:10.1002/polc.5070420313

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

年代:1973

数据来源: WILEY