摘要:

AbstractSome results obtained in the stereospecific polymerization of 2‐tert‐butyl‐1,3‐butadiene are reported. The catalysts employed were prepared from TiCl4and aluminum alkyls or soluble aluminum hydride derivatives. Polymers thus obtained were crystalline with a melting point of 106°C. and soluble in common solvents. X‐ray investigation shows the polymer to have a helical chain structure built on 11 monomeric units withcisconfiguration, distributed on three turns. The identity period along the chain axis is 15.3 A. A comparison of the infrared spectra of the crystalline and amorphous polymers is given. Attempts to obtain a crystalline 1,4‐transpolymer failed; this is in accord with the lower stability of such a configuration due to steric repulsion of the

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021001

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractThe effect of liquid sulfur dioxide concentration on cationic copolymerization of styrene (M1) with methyl acrylate (M2) was carried out with the use of boron trifluoride–ether complex as a catalyst. The reaction was carried out at 0°C. The monomer reactivity ratiosr1andr2increased with increase in liquid sulfur dioxide concentration, andr1was changed fromr1= 0.30 at [liq. SO2]0= 6.58 mole/l., tor1= 1.50 at [liq. SO2]0= 13.16 mole/l., butr2was not changed. These facts indicated that reactivity of carbonium ion of styrene in the propagation step was increased with increasing liquid sulfur dioxide concentration. The relation between the overall rate of copolymerization and liquid sulfur dioxide concentration is the same as in the case of the cationic homopolymerization of styrene, and polymolecular contribution of liquid sulfur dioxide on the overall copolymerization is shown from these observatio

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021002

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractThe radical polymerization of acrylonitrile was carried out in liquid sulfur dioxide and in benzene, with addition of aniline, dimethylaniline, dimethyl‐0‐toluidine, and diethylaniline to these systems. The temperatures of polymerization were 40, 50, and 60°C. It was found that the chain transfer reaction occurs more easily in liquid sulfur dioxide than in benzene; this was attributed to the differences in the polarity of the terminal radical of the growing chain in both solvents. The difference of activation energies due to the difference of bases is not so large. The frequency factors are rather important in both solvents for chain transfer reactions. The isokinetic relation is also discu

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021003

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractSince the observations of Edgar and Hill on polyhexamethylene adipamide/polyhexamethylene terephthalamide copolymers, a linear melting point/composition relationship has become widely accepted as a criterion for isomorphous replacement. In a series of binary copolymers based on homopolymers prepared from hexamethylene diamine andp‐phenylene dipropionic (3P3), 3‐(p‐carboxymethyl) phenyl butyric (2P4), 2‐(p‐carbomethoxy) phenyl propionic (3PO2), hydroquinone diacetic (2OPO2), terephthalic (T), adipic (6), or sebacic (10) acids, only the 6.3P3/6.3PO2 system showed a linear softening point/composition curve, although the differences in repeating unit length were certainly no greater and often much less than with adipic and terephthalic acids. X‐ray examination, however, revealed that all the systems behaved in the same basic manner, the second component dissolving in the lattice of the first until a certain critical concentration was reached when the lattice changed fairly abruptly to that of the second component in which the first component was now dissolved. The changeover point generally, but not always, coincided with the position of a minimum in the softening point/composition curve. Infrared and density measurements did not show any reduction in crystallinity at this point. These copolyamides, thus, afford no exception to the assumption that close similarity in length of repeating units is a necessary, but perhaps not the only, prerequisite for the occurrence of segmental change. The form of the softening point/composition curve is, therefore, not a reliable criterion for isomorphous replacement and it seems likely that this conclusion applies equally to the melting point/compos

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021004

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractIt is of considerable practical importance to be able to describe the distribution of molecular sizes of a polymeric material by a convenient mathematical expression. Since the various molecular averages of any distribution are obtained from a summation process, the general models require an analytical expression of the differential distribution and a corresponding definite integral generally having the integration limits of zero and infinity. In general, real polymer distributions do not fit these integration limits and an error, which can be very large, is therefore introduced. If the error in the various molecular weight averages due to changes in integration limits is of the order of or less than the error generally encountered in the experimental evaluation of the average, the distribution function can be considered to be applicable from a practical point of view. In addition, the selected model should fulfill the requirements of fitting known experimental facts such as: the polymerization kinetics, the effects of random degradation and crosslinking, fractionation data, and the effects of polymerization and processing on the differential distribution maxima. It should also conform to the rheological behavior based on current theoretical ideas. The integration limit criteria are applied to logarithmic normal type distributions, e.g., Wesslau, and generalized exponential type distributions, e.g., Schulz‐Zimm and Tung. The results show that logarithmic normal type distributions cannot be considered as useful models, while the generalized exponential type distributions can be valid and useful representation

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021005

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractIt is shown that logarithmic normal type distributions, e.g., Wesslau, cannot describe real polymer distributions having low and high molecular weight cut‐off values. However, certain cases of the generalized exponential type distribution do appear to be useful and valid model

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021006

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractIt is suggested that all of the morphological forms commonly observed in high polymers are closely related. These forms are considered to represent different stages in a development from single crystal into spherulite under the influence of species rejected by growing crystals. Single crystals undergo this transformation in habit when of a size roughly equal to δ =D/G, whereDis the diffusion coefficient in the crystallizing medium andGis the rate of crystal growth. New experimental results show that when δ is unusually large, single crystals may be grown from polymer melts, and when δ is reduced by the use of high molecular weight polymer and/or viscous solvents, spherulites may be grown from polymer solutions. It is shown that single crystals of polyethylene crystallized from solution in paraffinic solvents exhibit a different habit from those crystallized under equivalent conditions from xylene. This affords a simple explanation for the radialborientation found in spherulites of polyethyle

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021007

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractPolyether‐ester copolymers were prepared from methylp‐γ‐hydroxypropoxy benzoate and bis‐β‐hydroxyethyl terephthalate over the entire composition range by a condensation reaction. It was found by means of x‐ray diffraction that the copolymers showed high crystallinity over the entire range of copolymer composition. The melting point curve of the copolymers showed a eutectic type. The x‐ray diffraction patterns of the copolymers were different from both those of poly(ethylene terephthalate) and of poly(p‐1,3‐propylene oxybenzoate). These results showed that in each of the copolymers both the repeating units, the ethylene terephthalate unit and thep‐1,3‐propylene oxybenzoate unit, could be incorporated into the chain of a crystallizable polymer without hindering crystallization of the resulting copolymer, i.e., the copolymers were isomorphous over the e

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021008

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractCurrent polymer network theories exhibit inconsistencies which show up particularly clearly when one considers the three‐dimensional deformation (swelling) of networks which are prepared by crosslinking a polymer in solution. A check on the theories can only be obtained if one knows precisely the number of crosslinks in the network and if a range of deformations (range of swelling ratios) is imposed on the network. To this end a series of seven gels was prepared by crosslinking secondary cellulose acetate (D.S. = 2.42) in dioxane solution (5–10%) with dianisidine diisocyanate. The number of chemical crosslinks was determined by reacting unused isocyanate groups with C14‐labeled methanol. Subsequently, changes in the degree of swelling of the gel, induced by increasing concentrations of cellulose acetate in dioxane and methyl acetate solutions around the gel, were followed by measuring accurately the changes in length of 2‐cm. strips under a travelling microscope. At equilibrium swelling the activities of the solvent inside and outside the gel are equal. For the outside solutions the activities were derived from osmometry. The inside activities derive from a mixing term and an elastic deformation term. The mixing term was approximated by using the Flory‐Huggins expression with an interaction parameter, as obtained from osmometry on a derivative, which was prepared by reacting cellulose acetate with an excess of diisocyanate, thus avoiding network formation. By means of the various known theoretical expressions for the elastic deformation term, the swelling data allow the calculation of the number of crosslinks in the gels. All theories lead to far fewer crosslinks than are known to be there on the basis of the chemical analysis. This has never been observed to the same extent before, but may be specific for gels obtained by crosslinking in solution. One is forced to conclude that none of the existing theories are applicable. The data can be explained, however, by postulating that the configurations of the chains between crosslinks do not follow a Gaussian distribution, but are instead given by ω(r)dr = ωx(x)‐ωy(y)ωz(z)dxdydz, where ωx(x) =C|x|nexp { −bx2}. Such a non‐Gaussian distribution might arise because of topological restrictions, possibly including those due to the excluded volume. For the free energy of elastic deformation we find, following James and Guth's reasoning but using the new distribution function:\documentclass{article}\pagestyle{empty}\begin{document}$$ \Delta F_{{\rm e1}} /kT{\rm = }v[(n{\rm + 1)/2][}\lambda _x ^{\rm 2} {\rm + }\lambda _y ^{\rm 2} {\rm + }\lambda _z ^{\rm 2} {\rm - 3] - }vn{\rm ln }\lambda _x \lambda _y \lambda _z$$\end{document}wherevis the number of chains in the network and λx, λy, and λzare the deformation ratios with respect to the unstrained state. In the well known Gaussian theories, the termn+ 1 is absent and in front of the logarithm instead ofneither 0, 2/f, or 1 (f= functionality of the crosslink) is found, depending on whether the result of James and Guth, Flory and Wall, or Herman

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021009

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY

摘要:

AbstractCrosslinked polychloroprene samples were allowed to crystallize from the melt at various fixed elongations. X‐ray diffraction studies revealed that thecaxis becomes oriented toward the stretching direction, while theaandbaxes are randomly distributed about thecaxis. The alignment of the crystallitecaxes toward the drawing direction is much more perfect than that of the amorphous statistical chain segments prior to crystallization. This can be explained if we assume that the formation of a stable nucleus for crystallization requires the simultaneous alignment ofvamorphous segments. Thus, such measurements offer a means by which the critical size of the crystallization nuclei can be determined. The sizes deduced for polychloroprene vary with elongation from a cube 30 A. on a side at relative elongation α = 1.45 to a 17 A. cube at α = 7.40. Although our samples were not crystallized isothermally, these results are in qualitative agreement with nucleation theory. If the variation ofvcan, indeed, be estimated theoretically, then it will be possible to predict the entire crystallite orientation distribution in materials of this type from first principles. The orientation of crystallites formed in a sample at relative elongation α = 2.92 was found to be essentially independent of temperature from 24° C. to the melting point. For low degrees crystallinity, ω it is shown that a plot of 1/Tversus 1/(1 − ω)2is linear, thus permitting an evaluation of the melting point by extrapolation. Finally, the crystallite orientations were compared for a sample crystallized from the melt at α = 2.86 and for the same sample after further drawing to α = 3.50 at room temperature. The distribution in the latter case was considerably broader, which demonstrates the primary role played by interactions between crystallites in the cold drawing of partially crystallize

ISSN:0449-2951    

DOI:10.1002/pol.1964.100021010

出版商:John Wiley&Sons, Inc.    

年代:1964

数据来源: WILEY