Thermodynamic and Hydrodynamic Porperties of Linear Polymer Solutions. I. Light Scattering of Monodisperse Poly(α-methylstyrene)

Statistical Physics of Polymer Solutions: Conformation‐Space Renormalization‐Group Approach

Viscosity – Molecular Weight Relationships and Unperturbed Dimensions of Linear Chain Molecules

The unusual electronic and optical properties of many electroluminescent and conducting polymers arise from extended conjugation along the polymer backbone, which can also lead to insolubility, aggregation, and gelation. Synthetic efforts to produce an optimal structure require a balance between the persistence length and the effective conjugation length for the successful implementation of these materials in photonic and electronic devices. In this study, we have investigated the solution properties of a group of poly(phenyleneethynylenes) using a variety of light scattering techniques, including polarized and depolarized intensity measurements, dynamic light scattering, and size exclusion chromatography with a multiangle light scattering detector (SEC/LS). Interpretation of light scattering in the presence of absorption, fluorescence, and optical anisotropy is discussed. The molecular weights determined by light scattering encompassed the range from 10 105 to 5 106, with the root-mean-square radius of gyration as high as 250 nm. The results may be interpreted with a wormlike chain model to yield a persistence length of about 15 nm, so that these high-M polymers are coil-like in solution, rather than "rigid rods". This persistence length is still expected to be several times larger than the effective conjugation length.

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Equilibrium Flexibility of a Rigid Linear Conjugated Polymer

Osmotic pressures for branched polymers in a good solvent were measured over a wide range of concentrations. Two types of branched polymers, star-shaped poly(α-methylstyrene)s having three branches and comb-shaped polystyrenes having 15—16 branches, were studied. The data were analyzed using the scaling law. The difference in the reduced osmotic pressure between star-shaped polymers having three branches and the corresponding linear polymers results from the difference in radii of gyration. In branched polymers having many branches, there is a region from which the segments of other molecules are excluded as a result of high segment density.

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Osmotic Pressure of Semidilute Solutions of Branched Polymers

Further comments on the analysis of dilute solution data are provided. Light-scattering and intrinsic-viscosity data used for this purpose are those obtained for monodisperse polystyrenes, prepared anionically in tetrahydrofuran, in benzene, toluene, and dichloroethane at 30°C and in cyclohexane at temperatures ranging from 32.2 to 60.1°C. The value of [η]θ/M1/2 is somewhat greater than the corresponding value for Berry’s polystyrenes prepared anionically in benzene, where [η]θ is the intrinsic viscosity at the theta temperature and M is the polymer molecular weight. This suggests that the two types of samples differ in microstructure, though the precise difference is unknown. However, it is shown that the two-parameter relationships established experimentally in the previous papers are well reproduced in the present data. The relationships are different from those determined by Kato, et al., for monodisperse poly(α-methylstyrene) prepared anionically. Since there is shown to be no essential difference between our and their methods of determining mean-square radii, it seems unlikely that the difference is related to measurements and subsequent treatments. It is suggested rather that the problem is related to Kato’s samples.

/pdf/more-on-the-analysis-of-dilute-solution-data-polystyrenes-2tkamy99de.pdf

Thermodynamic and Hydrodynamic Porperties of Linear Polymer Solutions. I. Light Scattering of Monodisperse Poly(α-methylstyrene)

Citations

Statistical Physics of Polymer Solutions: Conformation‐Space Renormalization‐Group Approach

Viscosity – Molecular Weight Relationships and Unperturbed Dimensions of Linear Chain Molecules

Equilibrium Flexibility of a Rigid Linear Conjugated Polymer

Osmotic Pressure of Semidilute Solutions of Branched Polymers

More on the Analysis of Dilute Solution Data: Polystyrenes Prepared Anionically in Tetrahydrofuran

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