摘要:

AbstractThe equilibrium state of an infinite molecular weight, binary copolymer which is determined by next‐nearest neighbor placements of its counits is defined in terms of the conditional probabilities describing such placements and the standard state free energies governing them. The combinatorial method is used to derive the entropy of sequence length distribution, ΔSD. When ΔSDis combined with an expression for the energy of reaction which employs the standard‐state free energies of triad formation an expression for the copolymer's free energy is obtained. Since enumeration of the interrelationships among the possible triplets reveal three independent conditional probabilities, separate differentiations with respect to each of three conditional probabilities are equated to zero in defining the equilibrium state. These equations reduce to the more special case previously derived when only nearest‐neighbor effects are con

ISSN:0449-2994    

DOI:10.1002/polc.5070310102

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

年代:1970

数据来源: WILEY

摘要:

AbstractMethyl methacrylate has been polymerized at 40°C with VCl4‐AlEt3catalyst system in acetonitrile. A linear dependence of rate of polymerization on the monomer and catalyst concentrations as well as overall activation energy of 10.96 kcal/mole exhibits coordinated anionic mechanism. However, characterization of the structure of the polymer by NMR spectra revealed the presence of heterotactic units, whereas on the addition of hydro‐quinone to the catalyst system, the polymer obtained was a stereoblock. The mechanism of polymerization is discussed in the light of the kinetic studies and the structure of

ISSN:0449-2994    

DOI:10.1002/polc.5070310103

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

年代:1970

数据来源: WILEY

摘要:

AbstractA short survey is given of recent developments in polymer statistics. Through the many years since the original conception of the entropy derived from the large number of configurations of macromolecules by Mark and Guth the basic idea has never been subjected to doubt but not much progress has been made in the way of confirmation of quantitative theoretical relations.In quantitative relations quantities appear such as the effective number of chains in a network and also the energy differences between more and less elongated configurations which cannot be determined easily and have to be treated as adaptable parameters.On the other hand the theory of networks has been further developed so as to establish the exact physical meaning of the effective number of chains in a network. The theory of networks has also been extended to entanglement networks in which the entanglements have a finite life time. Based upon the Rouse‐Zimm treatment of viscoelastic dilute solutions on one hand and upon the generalized network model of Duiser and Chömff on the other hand, van Wiechen and Booy have developed a general theory of time dependent elasticity in concentrated polymer systems. This theory is briefly review

ISSN:0449-2994    

DOI:10.1002/polc.5070310104

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe light reflectance between 380 nm and 700 nm of one white, one black, six red, and six blue cellulose triacetate fabric samples was measured. Each measurement was carried out once on a dry sample and once on a sample immersed in water. From the data a numerical relationship was derived which permits the prediction of “wet” color from “dry

ISSN:0449-2994    

DOI:10.1002/polc.5070310105

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe conformational preferences oftrans‐1,2‐cyclohexanedicarboxylic acid (1,2‐CH) and ester derivatives have been studied. The optical rotatory properties of these compounds are discussed in comparison with those of other cyclic dicarboxylic acids. A stereoregular polymer, poly[ethylene‐(+)‐trans‐1,2‐cyclohexane dicarboxylate] (1,2‐CHPE) has been synthesized, and its properties are compared with those of

ISSN:0449-2994    

DOI:10.1002/polc.5070310106

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe uptake of water by polar polymers was shown by Simha and Rowen to be described by the Flory‐Huggins solution treatment at high relative vapor pressures. The breakdown at lower vapor pressures is attributed here to the effect of water content on the free volume of the system. By using data for the wool keratin‐water system, similar agreement is obtained for the rest of the isotherm by taking account of the volume changes observed at low vapor pressures. These are shown to set in at a characteristic composition with properties generally associated with a glass transit

ISSN:0449-2994    

DOI:10.1002/polc.5070310107

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe force required to stretch a polymer chain by 1% (fvalue) was calculated from experimental values of elastic moduliE1in the direction of molecular axis and the cross‐sectional area of the molecule of 25 well known polymers. Thefvalue is mainly dependent on the conformation of a molecule and almost independent of side groups. Thefvalues of polymers of various types of conformation may be summarized as follows: T type, 4−5 × 10−5dyne; TGTGtype, 1.5 × 10−5dyne; TG(3/1) type, 1 × 10−5dyne; T′G′ (7/2) type, 0.58 × 10−5dyne; T′G′ (4/1) type, 0.36 × 10−5dyne; TTGG type, 0.29 × 10−5dyne; where T, G, andGmeantrans, gaucheand minusgauche, respectively, and the numbers in the parentheses denote helical structures. The reason for an anomalous apparentE1value of nylon 6 (α‐form) previously reported was elucidated; it was confirmed thatE1exhibits a value expected for a polymer with a nea

ISSN:0449-2994    

DOI:10.1002/polc.5070310108

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

年代:1970

数据来源: WILEY

摘要:

AbstractPoly(ethylene sulfide) was prepared by a unique two‐step polymerization technique in which a “seed polymer” was initially formed, compacted to a desired bulk density, and then used to polymerize fresh ethylene sulfide monomer. The seed polymer was prepared by reacting ethylene sulfide with diethylzinc‐water in a suitable solvent. The final polymer was an exact magnification that faithfully reproduced any shape of seed used with regard to relative dimensions, angularities, curvatures and even imperfections. Poly(ethylene sulfide) prepared by this process can be used for successive polymerizations that proceed at the same rate as the original seed with comparable zinc content, and thus behaves as an “immortal” polymer. The high molecular weight polymer melts above 200°C, is highly crystalline, and is, insoluble in most organic solvents at ordinary temperatures. A number of solvents dissolve the polymer above 140°C at which temperature thermal degradation takes place. When the polymer is stabilized by use of certain thermal stabilizers, it can be successfully molded to give excellent physical and mechanic

ISSN:0449-2994    

DOI:10.1002/polc.5070310109

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

年代:1970

数据来源: WILEY

摘要:

AbstractThe dynamic mechanical properties, creep, and melting characteristics of a transparent polyethylene film prepared by a novel process of simultaneous high speed quenching and shear were examined. A high degree of orientation was attained in the process, the polymer chain backbone being aligned in the direction of shear. As a result of chain orientation, the dynamic in‐phase moduli in the temperature range from −160 to +120°C are about three to seven times the values for the compression‐molded material. Changes in β and α dispersion peaks are also noticed. The quench‐rolled film contains high melting point fractions which suggest very strongly the presence of thick crystals, perhaps up to about 1000 Å in thickness. Excellent resistance to creep, comparable to that of the cold‐drawn polyethylene,

ISSN:0449-2994    

DOI:10.1002/polc.5070310110

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

年代:1970

数据来源: WILEY

摘要:

AbstractStress‐strain isotherms at 25°C are reported for a series of unswollen networks ofcis‐1, 4‐polybutadiene which differ both in degree of crosslinking and in the volume at which the crosslinks were introduced. The former quantity was varied by variation of the amount of high energy radiation used to bring about the crosslinking, the latter, by crosslinking the polymer in solution as well as in the bulk, undiluted state. The results are interpreted in terms of the equationf*/(α−α−2) = 2C1+ 2C2α−1wheref*is the force per unit area of the undistorted, unswollen sample, α is the relative length of the sample, andC1andC2are empirical constants, the latter serving as a measure of the departure of the dependence of stress on strain from that indicated by the statistical theory of rubber elasticity. At equal values of the “modulus”f*/(α−α−2), the correctionC2is found to be very small for networks prepared in solution and to increase markedly with increase in concentration of polymer in the system undergoing crosslinking. In addition, the networks prepared in solution exhibit considerably smaller nonequilibrium, relaxation effects than those crosslin

ISSN:0449-2994    

DOI:10.1002/polc.5070310111

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

年代:1970

数据来源: WILEY