Poly-( I-butene) was separated into atactic and isotactic portions by extraction and these materials were individually fractionated. The two forms obeyed identical intrinsic viscosity-molecular weight relationships in good solvents; however, the isotactic modification exhibited lower values of the osmotic second virial coefficient for molecular weights below 7 x 10'.This type of behavior in good solvents has been reported by other workers for the two forms of polystyrene and polypropylene, and hence appears to be quite general. Precipitation temperature measurements in anisole gave a higher entropy parameter, $1, for the stereoregular poly-( 1-butene), in agreement with the result reported by Kinsinger and Wessling for polypropylene in phenyl ether. On the other hand, the latter workers found a lower theta, temperature for isotactic polypropylene, whereas we obtained a higher theta temperature for the stereoregular poly-( 1-butene). Thus, atactic poly-( 1-butene) is more soluble in anisole than its stereoregular counterpart for all molecular weights, whereas atactic polypropylene should be the form of lower solubility in phenyl ether for molecular weights above 39,000. Isotactic poly-( 1-butene) appears to have a more highly extended molecular conformation than its atactic counterpart, as judged from unperturbed dimensions estimated from light scattering data obtained using a good solvent. Parameters are given which permit a comparison of the relative extensions of a number of polyolefins. IntroductionThe method of preparation and the physical properties of a number of linear, stereoregular polyolefins were described by Natta and eo-workers in 1955.' Since that time there has been considerable interest in comparing the molecular dimensions and thermodynamic interactions of the isomeric forms of these polymers in solution. The majority of this work has involved the measurement of intrinsic viscosities, molecular sizes and second virial coefficients in thermodynamically good solveiits.2-11 The conclusions drawn from these investigat'ions are that the perturbed molecular dimensions in good solvents are indistinguishable for the atactic and isotactic forms, but that the stereoregular polymers exhibit smaller second virial coefficients (at least, for lower molecular weights) in these solvents. This latter conclusion is in agreement with the earlier work of Muthana and Mark,12 mho compared crystalline and amorphous samples of poly-(vinyl isobutyl ether). Finally, in the
synopsisPoly-4,4'-oxydiphenylenesulfonyl and poly-4,4'-methylenediphenylenesulfonyl were synthesized by an electrophilic substitution polymerization of the arylene monosulfonyl chloride monomers. The glass-transition temperatures T, of these polymers were determined by calorimetric and dynamic mechanical measurements, and the number-average molecular weights were determined by vapor-pressure osmometry. Both polymers were found to have the same T, at equivalent molecular weight; the limiting value a t high molecular weight is 238°C. Both polymers have two dynamic mechanical relaxation peaks at temperatures far below T,. One is in the neighborhood of O"C, and the other is at -110°C. Plausible origins for these relaxations, and the absence of any near 0°C in poly(4,4'-isopropylidenediphenylen~,4'-~~1lfony~diphenylene dioxide), are discussed. 14. J. M. Barrales-Rienda and D. C. Pepper, J . Polym. Sci. B, 4,939 (1966). riam, J . Po/ym. Sci. A-1, 5 , 2378 (1967).
Fractionation of polymers is usually done on a very small scale where only viscosity, and possibly molecular weight measurement are made on the fractions. The elution fractionation system offers a possibility of fractionating on a sufficiently large scale to permit a thorough study of physical properties as a function of molecular weight. The elution column method was scaled up to fractionate one pound of polymer. Facilities were made so that the column could operate over a temperature range of 25 to 135°C. Each fraction was eluted by a separate solvent‐non‐solvent, mixture. The elution column was packed with Celite and the flow of the solvent‐non‐solvent mixture was controlled by a pumping system. Total fractionation time was 20 hours. The column temperature could be controlled to permit any temperature heating or cooling profile. The large scale elution column has been used to fractionate low and high density polyethylenes, ethylene copolymers, and polybutene‐1. Sufficient amount of polymer was obtained in each fraction to permit a study of mechanical properties as a function of molecular weight. From these fractions the effect of synthesized bimodal distributions on the melt flow and physical properties was investigated.
synopsisPolyethylene which was made by emulsion polymerization was characterized by means of osmometry, light Scattering, and viscometry. The samples have unusually high weight-and number-average molecular weights. Low molecular weight polymer which is usually present in commercial polyethylenes was not detected. The data indicate a compact, highly ramified molecular structure. The light-scattering data suggest each latex particle is made up of essentially one giant molecule which swells but does not dissolve in organic solvents a t 1 0 0 O C . Swelling factors calculated from viscosity and lightscattering data indicate low degrees of crosslinking. A clear distinction cannot be made between a highly long-chain branched structure and the crosslinked structure of microgels. Of the low-density polyethylene, 1-2 wt.-% is made up of molecules which have a comparable structure. In contrast, the greatest portion of the experimental samples is composed of the high molecular weight, highly ramified molecules.
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