Solutions In Good Solvents Research Articles

Osmotic pressures of concentrated polymer solutions in good solvents

AbstractThe hydrodynamic radii of solvated polymer molecules can be estimated with a theory which has been reported earlier. These radii are employed in a hard sphere model to predict osmotic pressures of polymer solutions. Calculated and experimental osmotic pressures are in quite good agreement even for solutions with concentrations appreciably higher than the critical concentrations for overlap of polymer coils. The theory presented here is limited to good solvents.

Resorbable materials of poly(L-lactide)

Poly(L-lactide) PLLA materials with various porosity in the range of 5 to 300 Μm were produced by crystallization of the polymer in presence of low molecular weight additives from solution in good solvents, followed by the diluent extraction. For the concentration of diluent in PLLA in the range of 10 to 50 per cent by weight, the pore size increased with increasing concentration of additive, while the additive was easily extracted from the polymer. For the concentration of additive in PLLA in the range of 60 to 80 per cent by weight, the pore size increased or/and decreased with increasing concentration of the additive, while the latter was hardly extractable from the polymer. Porous, resorbable tubes or rods of various diameter well accepted by living organism were produced by this method. Tracheal prostheses, pins or porous reservoirs made from PLLA or modified porous PLLA could be some of many potential application of these materials.

Scaling theory of polymer adsorption : proximal exponent

We interpret some recent calculations of Eisenriegler, Kremer, and Binder [1], and related multi-critical results of Diehl and Dietrich [2]. They show that the monomer concentration profile Φ(x) for isolated polymer chains in a good solvent and in close proximity to an adsorbing wall exhibits a singular behaviour ; i.e., Φ(x) ∼ (a/x) m, where a is a monomer dimension and m ≅ 1/3. Taking into account the proximal exponent m, we correct earlier scaling results [3, 4] for the interfacial tension of semi-dilute polymer solutions in good solvents. We also find good agreement with a recent result by Ishinabe [5] on the single chain energy.

Conformation of poly(isoprene‐gstyrene) in dilute solution

AbstractA detailed description of the synthesis of a model poly(isoprene‐g‐styrene) is given. From light scattering measurements the real radius of gyration of the polyisoprene is backbone is found to be smaller than that of the polystyrene branches. The core‐and‐shell conformation of graft copolymers in dilute solution in good solvents, which was proposed for poly(styrene‐g‐isoprene), is supported by these results.

Dynamical properties of dilute flexible polymer solutions

We analyse the dynamical properties of dilute Polymer solutions by using scaling arguments. To this end, we generalize the scaling analysis proposed for the static properties of these solutions by introducing a dynamical exponent z. This exponent has two slightly different values for theta and good solvents. In order to compare our results with experiments, we suppose that z has its Zimm value (z = 3) in theta solutions, and another value (z = 2.9) which we pick from recent experimental results, for solutions in good solvents. We calculate the temperature, molecular weight, and scattering vector dependences of different observable quantities such as the diffusion constant, the characteristic times and frequencies, the viscosity, etc. Our results are in good agreement with experiments. They show how these dependences deviate from the classical patterns of behaviour as we change from z to z. In particular, it is found that the diffusion coefficient in a good solvent does not obey Einstein's law. The analysis is then extended to some time dependent properties, such as the dynamic viscosity and the real part of the complex modulus. It is shown that these properties exhibit cross-overs. Universal coordinates are proposed for their study. Finally, a criticism of the so called reduced variables coordinates is given. Another set of variables is given, which is valid for both low and high frequencies, whereas the usual method failed for high frequencies.

Dynamical Properties of Polymer Solutions in Good Solvent by Rayleigh Scattering Experiments

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDynamical Properties of Polymer Solutions in Good Solvent by Rayleigh Scattering ExperimentsM. Adam and M. DelsantiCite this: Macromolecules 1977, 10, 6, 1229–1237Publication Date (Print):November 1, 1977Publication History Published online1 May 2002Published inissue 1 November 1977https://doi.org/10.1021/ma60060a014RIGHTS & PERMISSIONSArticle Views737Altmetric-Citations256LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (971 KB) Get e-Alerts Get e-Alerts

Interpretation of light scattering in moderately concentrated polymer solutions

AbstractLight scattering curves of moderately concentrated polymer solution in good solvents show increasing curvature at higher concentrations in the range of small scattering angles. An attempt was made to separate the scattering curves into their intra‐ and intermolecular contributions and draw conclusions concerning the radial distribution function of the molecular centers of gravity in solution. The results obtained suggest the formation of a network of overlapping coils as the structure model for such systems. Model calculations on rotational ellipsoids showed that preferential parallel orientation of coils having no spherical symmetry may offer an explanation for the peculiar behavior of the intra‐ and interparticular scattering functions, which was derived from experimental data.

Polydispersity characterization by light scattering for polymers in good solvents

Light scattering data are used to obtain the M ̄ z/ M ̄ w polydispersity index for polymers in solution in good solvents. Due to the fact that light scattering data analysis already requires some information about the polydispersity of the sample, a successive approximation method is proposed. The results obtained for several samples are in good accord with independent determinations. In the case of a series of fractions from a given fractionation, the polydispersity indices show a close similarity with theoretical results given by Tung for comparable cases.

Unperturbed molecular dimensions of atactic polybutene-1 at different temperatures

The unperturbed dimensions of atactic polybutene-1 have been determined by viscosimetric measurements in θ solvents over the range −46° to +83°. Additional data on unperturbed dimensions, calculated by the Kurata-Stockmayer approximation from studies of solutions in good solvents, are suitable to extend the range of temperature to 100°. From all calculated and measured quantities, the following temperature coefficient is found: d 1 n r 2 0 dT ·10 3=−1·2±0·2 This value is compared with that obtained by thermoelastic measurements, which give a positive value for the coefficient: the possible causes for this fact are discussed.

Influence of Hydrodynamic Interaction on the Viscoelastic Behavior of Dilute Polymer Solutions in Good Solvents

The treatment by Ptitsyn and Eizner of the dynamics of dilute polymer solutions for dominant hydrodynamic interaction, taking into account excluded volume effects, is extended to the general case for changing hydrodynamic interaction. The function Φ (h, ε) is tabulated for selected values of ε, the parameter which accounts for the expansion of the coil due to excluded volume effects. An approximate derivation of the storage and loss moduli from this theory is proposed. According to this calculation, an increase in ε causes a shift of the frequency dependence of the moduli from Zimm-like toward Rouse-like behavior. The determination of ε from experimental data is discussed.