Claude Strazielle

Effect of alcohol on the properties of micellar systems: I. Critical micellization concentration, micelle molecular weight and ionization degree, and solubility of alcohols in micellar solutions

Additions of alcohols of medium chain length (butanol to hexanol) to micellar solutions result in a decrease of critical micelle concentration and micelle molecular weight, and an increase of the micelle ionization degree. Moreover, the micelle molecular weight (or surfactant aggregation number) at a given alcohol concentration increases with the surfactant concentration and may reach values larger than in the absence of alcohol. Striking differences have been found in the changes of molecular weight of TTAB micelles in H/sub 2/O-pentanol mixtures in the presence of 0.1 M KBr and in the absence of salt. These various results have been explained by considering the effect of the micelle solubilized alcohol on the micelle surface charge density and on the dielectric constant of the palisade layer. 48 references.

Characterization and conformation of aromatic polyamides: poly(1,4-phenylene terephthalamide) and poly(p-benzamide) in sulphuric acid

Abstract The dilute solution properties of two aromatic polyamides, poly(1,4-phenylene terephthalamide) (PPDT) and poly( p -benzamide) (PBA) in 96% sulphuric acid, have been investigated by measurements of the intrinsic viscosity, by light scattering and by gel permeation chromatography (g.p.c.). The Mark—Houwink relation for PPDT indicates that the conformation is intermediate between a coil and a rod-like particle. The conformations of both aromatic polyamides have been determined precisely by coupling g.p.c., light scattering and viscosity and it was found that PPDT and PBA in 96% sulphuric acid are not very rigid particles. The rigidity has been characterized in terms of a worm-like chain. The persistence lengths q which evaluate the rigidity of the chain are q = 175 ± 25 A for PPDT and q = 500 ± 100 A for PBA has the more rigid polymer chain.

Cyclic macromolecules. Synthesis and characterization of ring-shaped polystyrenes

Abstract A method has been developed to synthesize cyclic polystyrene molecules, by reacting bifunctional “living” polystyrene with α,α′ dibromo- p -xylene. The ability of the method to yield cyclic polymers over a molecular weight range from 7000 to 250,000 has been thoroughly investigated and discussed. Characterization of the cyclic macromolecules with respect to linear homologues of the same molecular weight has been performed by means of viscometry. The effect of cyclization tends to decrease as the molecular weight increases.

Optical anisotropy of a worm-like chain and its application to the determination of the persistence length in an aromatic polyamide

Abstract The optical anisotropy, as obtained from the depolarization of light scattering, has been evaluated for a worm-like chain as a function of the segment anisotropy δ 0 and of the ratio of the contour length L to the persistence length q . The comparison between the theoretical curves and the experimental data obtained for an aromatic polyamide [poly( para -phenylene terephthalamide)] in a range of DP from 7 to 30 leads to a value of q in good agreement with that calculated from other methods requiring a wider range of molecular weights.

Effect of alcohol on the properties of micellar systems

Additions of alcohols of medium chain length (butanol to hexanol) to micellar solutions result in a decrease of critical micelle concentration and micelle molecular weight, and an increase of the micelle ionization degree. Moreover, the micelle molecular weight (or surfactant aggregation number) at a given alcohol concentration increases with the surfactant concentration and may reach values larger than in the absence of alcohol. Striking differences have been found in the changes of molecular weight of TTAB micelles in H/sub 2/O-pentanol mixtures in the presence of 0.1 M KBr and in the absence of salt. These various results have been explained by considering the effect of the micelle solubilized alcohol on the micelle surface charge density and on the dielectric constant of the palisade layer. 48 references.

Characterization of polyazomethines in dilute solution. Correlation between the light scattering parameters and the u.v.-visible absorption spectrum

Abstract The high values 1 (up to cm 3 g −1 ) of the refractive index increments d n d c of sulphuric and methane sulphonic acid solutions for a series of polyazomethine compounds at 546 and 628 nm are related quantitatively to the existence of a strong absorption band around 400 nm. The frequency dependence is well explained by the anomalous dispersion calculated from the decomposition of the absorption band into Gaussians. The blue shift and hypochromic effect, and the correlated decrease in d n d c , resulting from an aggregation process in methane sulphonic acid can be interpreted by a side-by-side arrangement of aggregates. This result is substantiated by a calculation of the optical anisotropy from the depolarized part of the scattered light.

On the Molecular-weight Determination of Bisphenol-a Polycarbonate

Abstract In order to assess the reliability of absolute molecular weights of bisphenol-A polycarbonate samples measured by size exclusion chromatography, the results obtained from two experimental systems and two calibration methods are compared with each other as well as with data provided by light scattering determinations. The interest of coupling a light scattering detector to the chromatographic system is discussed.

Preferential Solvation in the Ternary System Polystyrene-Benzene-Methanol

Abstract The preferential sorption coefficient A in the ternary system polystyrene (3)-benzene (1)-methanol (2) has been determined in dilute solutions by light scattering. A series of linear (especially of low molecular weight) and well defined comb-like and star-shaped polystyrenes has been studied. The solvation is very strongly dependent upon polymer segment density (or volume fraction of polymer inside the coil) where coefficients a and b depend mainly on the thermodynamical interaction parameters, and Λ∞ is the preferential sorption coefficient of polystyrene with an infinite molecular weight. The conclusions of this study have been extended to moderately concentrated polystyrene solutions.

Light scattering study of stereocomplex behaviour in solutions of poly(methyl methacrylate)

Abstract The behaviour of mixtures of iso- and syndiotactic poly(methyl methacrylate) (PMMA) as a function of time and polymer whole concentration in several solvents has been studied by light scattering and laser light scattering. The different solvents investigated in this study are acetonitrile, ethyl acetate, dimethylformamide (DMF), tetrahydrofuran (THF) and 1,4-dioxane. We have found that the last one behaves as a weakly complexing solvent, while the others show a complexing power decreasing from acetonitrile to THF. An increase in polymer whole concentration induces a higher aggregation of the macromolecular coil, while the compaction process of stereocomplex particles is not strongly influenced. The influence of time in stereocomplex behaviour depends on the nature of the solvent employed. In strongly complexing solvents there is initially a strong increase in the aggregation process and a decrease in compaction. However, in weakly complexing solvents these kinetic processes are less important.

Total and preferential sorption in polar ternary systems

In this paper we have applied the Flory–Huggins and Flory–Prigogine theories to several polar ternary systems of the type polymer–liquid 1–liquid 2. From light scattering and viscosity measurements we have calculated several experimental parameters necessary to calculate the total sorption function, Y, and preferential sorption coefficient, λ.We have tested the Flory–Huggins and Flory–Prigogine theories using the following four systems PMMA–1,2-dichloroethane–acetonitrile, PMMA–1,2-dichloroethane–ethyl acetate, PMMA–dimethylformamide–acetonitrile and PMMA–dimethylformamide–ethyl acetate. We have found that the Flory–Prigogine theory leads to a better description of the sorption phenomena. For most of the investigated systems, we have found that the value of the surface to volume ratio, S3, for PMMA that best fits the theoretical and experimental data is 0.38 × 108 cm–1. However, it is necessary to investigate a higher number of ternary systems in order to obtain more accurate conclusions.