摘要:

AbstractInternal viscosity models (IVM) for dilute‐solution polymer dynamics differ in how they define the deformational forceFdwhich includes φ, the IV coefficient, and in how they treat polymer rotational velocity Ω. Here, the handling of angular momentum is shown to be crucial. A torque balance in simple shear flow at shear rateGleads to stress symmetry and specification of Ω(G) which differs greatly from the conventional Ω =G/2. This determines theGdependence of viscosity η and normal stress coefficient ζ. There are also implications of a transition in rotational behavior as φ approaches a critical value. Predictions of η(G), ζ(G), and η*(ω) are presented for two versions ofFd: one derived recently by the authors and one being most commonly used at present. Limiting cases for high and low φ, and for high and lowGand ω, are discussed. Some differences exist between predictions of the twoFdmodels, but these are surp

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120501

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effect of molecular weight distribution on mechanical properties of concentrated polymer solutions was studied by measuring creep compliance and complex modulus for solutions of binary blends of narrow distribution polystyrenes in chlorinated biphenyl. Two‐step plateaus in the rubbery plateau region, as reported for undiluted polymer blends, were observed for concentrated solutions provided the molecular weights of component polymers differed greatly. Thenth order blending law (n= 1, 2, 3) of Bogue et al. was simplified in form to compare with experimental results. As far as the present version of simplification was concerned, the cubic blending law was better than the quadratic one in describing viscoelastic properties of polymer blends. The cubic blending law reproduced closely the magnitudes of viscoelastic functions such as loss modulus and relaxation modulus but it was not able to predict the two‐step plateaus, even when the ratio of molecular weights of components was as large as 10. It also provided a good approximation to reported results on the steady‐state complianceJ ebofor undiluted binary polymer blends and present results for solution blends. Since the cubic blending law in the simplified version was consistent with previous results on concentration dependence of the steady‐state compliance for concentrated solutions of narrow distribution polymers, it gave a unified expression for the steady‐state compliance of binary polymer blends and concentrated solutions of narrow distributi

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120502

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractA series of polystyrenes with weight‐average molecular weight M̄wup to 1.3 × 107was prepared by anionic polymerization in tetrahydrofuran (THF). Each sample was characterized by gel‐permeation chromatography, light scattering, and viscometry. It was found that each sample had an almost symmetrical and very narrow molecular weight distribution (M̄w/M̄n<1.07). The mean‐square unperturbed radius of gyration 〈S2〉0was determined intrans‐decalin at 20.4°C as 〈S2〉0= 7.86× 10−18M̄w(cm2). The particle scattering factor was well represented by the Debye equation irrespective of solvent in the range of M̄w<4 × 106, and only a small deviation was observed in benzene at higher molecular weights. The penetration function Ψ ≡A2M2/4π3/2NA〈S〉23/2was found to approach a relatively low asymptotic value of 0.21–0.23 at molecular weights above 2 × 106in benzene at 30°C, whereA2is the second virial coefficient andNAis Avogrado's number. It was also found that the theta temperature intrans‐decalin was affected by the nature of polymer samples. A difference of about 3°C in the theta temperature was observed between two series of anionic polystyrenes, one prepared in THF and the other in benzene, but there was practically no

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120503

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractIf the counterion of a polyelectrolyte is not identical with any of the ions of a low molecular weight electrolyte added to the solution, the system may be regarded as a four‐component system. Relations for the refractive index increments have been derived which allow the determination of the coefficient of selective sorption of the added electrolyte from the refractive index increments of the components independent of the original counterion of the polyelectrolyte. Equilibrium dialysis and differential refractometry were used to study the interaction of KCl, KBr and NaI with poly[‐1(2‐hydroxyethyl)pyridiniumbenzenesulfonate methacrylate] or with an analogous polymer containing a toluenesulfonate counterion in aqueous solutions. The coefficient of selective sorption increases in the series Cl−

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120504

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe 22.6‐MHz Fourier‐transform noise‐decoupled13C (carbon‐13) NMR spectra of several ethylene–vinyl acetate (E–VA) copolymers were obtained. We found that triad information on monomer placement can be deduced from carbonyl resonances, triad and pentad information can be deduced from methine carbon resonances, and triad information is available from the methylene carbon resonances. The random comonomer distributions in E–VA polymerizations were demonstrated up to pentad placements. In addition, the use of model‐compound data in the analysis of copolymer sp

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120505

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe polymeric hydrogen form of phthalocyanine is found to be more conductive than the metallic derivatives, in contrast to the behavior of the monomers. In addition, the polymers were found to be much more conductive than the corresponding monomers with the resistivity of the polymers ranging from 7 ohm‐cm to about 3 × 106ohm‐cm. The polymers were found to have moderately high dielectric constants ranging from 16 to 1300 at room temperature, depending upon the applied pressure. Based on the dependences of the conductivity and permittivity upon the electric field strength, the average molecular length of the conductive paths within the polymer molecule has been estimated to be 100–1000 Å. In view of these estimated lengths, together with the exponential dependence of the permittivity and conductivity upon the pressure and temperature, the dispersion of the dielectric constants in the range of 10–100 KHz, and the chemical architecture of these ribbonlike polymers, the electronic behavior of these polymers is concluded to be consonant with the model of essentially one‐dimensional conduction within and along the chains by freed charges. Much as in a number of previously studied highly conjugated polymers, the present polyphthalocyanines are semiconducting and exhibit nomadic polarization, with dielectric constants ranging from

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120506

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThe chemical and physical crosslink densities of irradiated polybutadiene were determined using a precise and consistent method. This method included the use of a statistical theory of crosslinking modified to include chain reactions and the use of Langley's theory for calculating the number of trapped chain entanglements. The number of crosslinks formed per unit radiation dose,G(X), was measured for a series of polybutadienes containing various isomeric forms of unsaturation. The physical crosslink density and the molecular weight between entanglements were determined from measurements of the compression modulus of swollen samples.

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120507

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractLight‐scattering, osmotic pressure, and viscometric studies on fractions of cellulose acetate (degree of substitution 2.45) in three solvents are described. The data yield the dependence of the mean‐square radius of gyration 〈s2〉, the second virial coefficient Γ2, and the intrinsic viscosity [η] on molecular weightMand temperature. The results are interpreted to show that excluded volume effects on 〈s2〉 are negligible, even though Γ2is large anddΓ2/dTis positive. The large experimental value ofdIn [η]/dInMis interpreted in terms of partial draining effects. Data on 〈s2〉 and [η] for other cellulose esters in the literature are similarly interpreted. Significant aggregation found in solutions of cellulose acetate in many

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120508

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractInjection‐molded specimens of nylon 6 were examined by x‐ray diffraction as a function of depth in three characteristic directions. A skin and a core were always found to be present which differed in the degree of crystalline perfection and crystal modification. While the core of pure nylon 6 was found to be not oriented, the core of specimens containing nucleating agents was found to contain a typical texture of the monoclinic modification of nylon 6 in which the distribution probability of thea*andc*axes resembles ellipsoids with three unequal axes. A model explaining this texture as due to degenerated (deformed) spherulites is proposed. With a transcrystalline nylon 6 specimen the direction of the fastest growth in the unit cell (which forms the radius of spherulites) is found to be close to theaa

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120509

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY

摘要:

AbstractThermoelectrets of poly(methyl methacrylate) were exposed to various atmospheres of known relative humidity between 0 and 100% and the thermal current spectra analyzed. The study of the decrease of the heterocharges as a function of the exposure time reveals important differences in stability between the three peaks of the spectrum; the two peaks appearing at low temperatures can be attributed to a uniform volume polarization, and the third peak observed at high temperature to a space charge polarization. The shift of the peaks indicates plasticization of the polymer by water vapor. This effect is reversible when the samples are exposed for a sufficiently long time to a drying atmosphere. The complex variations of the initial rise of the spectrum as a function of the exposure time show that the activation energy of the peaks probably depends upon the degree of hydration of the polymer.

ISSN:0098-1273    

DOI:10.1002/pol.1974.180120510

出版商:John Wiley&Sons, Inc.    

年代:1974

数据来源: WILEY