The average configuration of polymer molecules in solution is markedly influenced by the obvious requirement, ordinarily disregarded in problems relating to molecular configuration, that two elements of the molecule are forbidden from occupying the same location in space. The influence of spatial ``interferences'' between different segments of the molecule on its average configuration has been investigated by statistical and thermodynamic methods.It is shown that if the average linear dimension of a polymer chain is to be taken proportional to a power of the chain length, that power must be greater than the value 0.50 previously deduced in the conventional ``random flight'' treatment of molecular configuration. This power should approach 0.60 for long chain molecules in good solvents. With increase in size of the solvent molecule, the influence of interference on molecular configuration diminishes, vanishing entirely in the extreme case of a solvent which is also a high polymer. The effect of a heat of in...

The Configuration of Real Polymer Chains

A photoelectric photometer designed for the measurement of absolute turbidity, dissymmetry, and depolarization of dilute solutions of high molecular weight materials, and hence determination of their molecular weights, is described. The photometer comprises essentially a monochromatic parallel primary beam of radiation, a six-sided scattering cell for measurements at 0°, 45°, 90°, and 135°, a multiplier phototube and galvanometer, a standard opal glass diffusor, and removable polarizer and analyzer. Turbidity is determined in terms of a ratio of deflections for the 90° scattering and for the primary beam reduced in intensity by neutral filters and diffused by an opal glass plate. Working relationships leading to determination of absolute turbidity are developed. These relationships include corrections for refraction and reflection effects, and for imperfect diffusion by the opal glass. The latter is evaluated by comparison of the opal glass with reflecting diffusors corrected for specular component of reflectance. The response of some multiplier photo-tubes is shown to be dependent on the plane of polarization of the incident radiation. Data illustrating the performance of the photometer include comparison of molecular weights of polystyrene fractions, beta-lactoglobulin, bovine serum albumin, lysozyme, sucrose octaacetate, Raleigh’s ratio and depolarization for benzene, turbidity of a “standard” polystyrene, and particle size of a GR-S latex, with data obtained by other methods or other investigators.

Photoelectric Light-Scattering Photometer for Determining High Molecular Weights*

Using light scattering, the mean square molecular radius and length of a number of samples of polystyrene have been measured as a function of solvent and temperature. Molecular weights, intrinsic viscosities, and ``osmotic second virial coefficients'' have also been determined on many of the samples. From the data it may be concluded: (1) that polystyrene molecules are extended and stiffened by steric interactions of the phenyl groups; (2) that the molecules are largely unbranched; (3) that the heat of dilution is negative in some solvents, contrary to the usual situation in hydrocarbon systems; (4) that the osmotic second virial coefficient depends strikingly on molecular weight for a given solvent; (5) that there is a good correlation between this coefficient and the mean square radius at a given molecular weight; (6) that the intrinsic viscosity is strictly proportional to a power of the molecular weight over the molecular weight range from 2,000 to 2,000,000, but that deviations occur at lower molecular weights; (7) that the intrinsic viscosity and mean square radius are functions of solvent at high molecular weights but not at very low molecular weights. Theoretical concepts necessitated by these observations are discussed briefly.

Light Scattering Investigation of the Structure of Polystyrene

In recent years linear polymers containing transition metals have attracted much interest. There are two types of organometallic polymers in which the metal-containing portion is either a part of the polymer main chain or bound to the polymer as a pendant group. In this article the recent studies on the former type of linear polymers are reviewed on the basis of the following three parts: 1 metallocene-containing polymers; 2 linear “Werner-type” coordination polymers; 3 polymers containing sigma-bonded transition metals in the main chain. The main part of this review is devoted to a new class of soluble metal-poly-yne polymers in which transition metal atoms are joined in the main chain by a metal-carbon σ-bond.

Linear polymers containing transition metals in the main chain

Whereas extensive efforts have been directed recently toward improving the mathematical exactness of the statistical mechanical theory of polymer solutions, fundamental limitations set by the nature of the physical approximations have not received adequate attention. A careful comparison between theory and experiment in dilute solutions reveals a large discrepancy between the calculated and the observed departures from the ideal entropy of dilution. The assumption of random occupancy of lattice sites by polymer segments, which is employed in previous treatments, is at fault. In very dilute solutions of high polymers the solution is microscopically discontinuous. Two regions of the volume can be distinguished: one is totally unoccupied by segments of polymer molecules; the other consists of regions encompassed by the irregularly coiled polymer molecules. In the latter the concentration of lattice cells occupied by polymer segments is determined by the configuration of the polymer molecule, being independen...

Thermodynamics of Dilute Solutions of High Polymers

Comparative Osmotic and Viscosity Measurements with Polystyrene Fractions

1. The specific viscosity of a dilute solution of polystyrene or rubber is strongly dependent on the nature of the solvent; the specific viscosity is high in a good solvent, and low in a poor solvent or a solvent-nonsolvent mixture. This has been interpreted as being due to changes in mean molecular shape. The specific viscosities of cellulose acetate solutions are not so sensitive to the nature of the solvent. 2. The extrapolated specific viscosity at the limit of solubility is in the same range for several different solvent-nonsolvent systems. 3. The effect of a temperature increase is to lower the specific viscosity of rubber or polystyrene solutions in a good solvent, but to increase the specific viscosity in a mixture of solvent and nonsolvent. 4. The specific viscosity of a dilute polystyrene solution is more nearly linear with concentration in a toluene-methanol mixture than in pure methanol. The quadratic term b in the equation: (ηsp=ac+bc2), is reduced relatively more than the linear ter...

The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High Polymer Solutions

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Comparative Osmotic and Viscosity Measurements with Polystyrene Fractions

The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High Polymer Solutions

The Effect of Temperature and Solvent Type on the Intrinsic Viscosity of High Polymer Solutions