Dominique Sarazin

Properties of ethylene oxide-propylene oxide statistical copolymers in aqueous solution

Abstract This paper presents a thermodynamic study of aqueous solutions of ethylene oxide-propylene oxide statistical copolymers. In a first step, copolymer samples are carefully characterized by elemental analysis, 1 H and 13 C nuclear magnetic resonance, gel chromatography and light scattering. Secondly, the lower critical solution temperature is studied as a function of copolymer composition and concentration. This phase separation behaviour as well as the temperature dependences of intrinsic viscosity, second virial coefficient, Flory interaction parameter χ and partial specific volume are discussed in the background of different polymer theories.

Identification of the formation of aggregates in PEO solutions

The properties of poly(ethylene oxide) PEO chains (molecular weight Mw: 6500) have been examined in dilute solutions in methanol using static (SLS) and dynamic (DLS) light scattering. The ability of PEO chains to aggregate depends on the history of the sample. Thus two relaxation times have been observed in the correlation functions of the intensity of the light scattered by PEO in methanol when the sample was previously dissolved in hot water (t≥60°C). The fast mode is attributed to the well-solvated monomolecular species and the slow mode is because of the formation of aggregates that are generated by hydrophobic interactions. These aggregates are well defined, relatively monodisperse and very stable. No aggregation is observed for PEO in methanol when the sample has been previously dissolved in a lot of solvents such as water (t=30°C), chloroform, dioxane, dimethylsulfoxyde (DMSO), dimethylformamide (DMF) or acetonitrile.

Relation between physical gelation and tacticity in polystyrene

Abstract In order to throw some light on the physical gelation of polystyrene in solution, we have prepared samples of differing tacticities by means of epimerization of an isotactic sample. After careful characterization by 1H nuclear magnetic resonance, light scattering, viscometry and gel permeation chromatography, the gelation propensity has been studied by differential scanning calorimetry and the ball-drop method in carbon disulphide (CS2) and in diethyl malonate. For a fraction of isotactic triads higher than 58%, gelation characteristics remain those of isotactic polystyrene. Between 58 and 35%, no gelation occurs whatsoever. Below 30%, the gelation characteristics of atactic polystyrene are retrieved only in CS2. The main conclusion is that the gelation phenomenon in atactic polystyrene in CS2 is due to the syndiotactic sequences.

Effect of additives on solution properties of ethylene oxide-propylene oxide statistical copolymers

Abstract In this paper, the effect of different additives on the solubility and intrinsic viscosity [η] of ethylene oxide-propylene oxide statistical copolymers in water is studied. In the case of mineral additives, the order of ‘salting out’ is the same as for ethylene oxide homopolymer. If one excepts the case of sodium iodide, the variations of the viscosimetric expansion can be plotted on the same curve as a function of reduced temperature for different salts. Organic additives have an increasing or decreasing effect on the lower critical temperature (LCST′) of the copolymers according to their polarity. The relation between the variations of [η] and LCST′ is much more complex than for mineral additives since [η] at a given temperature depends on the free energy of mixing of the two solvents.

Automatized photogoniodiffusometer and coupling with automatized viscosimeter

SummaryWe describe an automatized light scattering apparatus and its coupling with automatic viscosimeter and give some applications.The laser technique development motivated several workers to construct various kinds of light scattering apparatus (1,2). Nevertheless, at our knwledge, a entirely automatized device with automatic dilution which avoids many fastidious handling has never been proposed. Moreover, the usual characterization of a polymer sample often requires, not only his molecular weight Mw and radius of gyration RG but also its intrinsic viscosity [n]. One of us (3) has, some years ago, constructed an automatic viscosimeter. Thus, it was natural to associate, in a same apparatus, the two types of technique, in order to determine, in a same experiment requiring only the preparation of one solution, the principal molecular parameters characterizing a polymer sample and its interaction with a given solvent.

Effect of the carboxylate group distribution on potentiometric titration of acrylamide-acrylic acid copolymers

Summarythe potentiometric behavior of acrylamide-acrylic acid copolymers is discussed as a function of their method of preparation: base hydrolysis of polyacrylamide or radical copolymerization. The values of pK0 (the intrinsic pK at zero degree of ionization) and the variations of pKa versus the ionization degree are found to depend on the origin of the polymers and such differences are qualitatively attributed to significant discrepancies in the carboxylate group distribution.

Influence of nonionic surfactant on aggregation state of scleroglucan in aqueous solution

The interactions between nonyl phenol polyethylene oxide and scleroglucan are investigated by turbidimetry, viscosimetry filterability tests and measurements of elastic modulus and adsorption. The phase diagrams of this ternary system have been established as a function of temperature and composition. It is shown that the surfactant molecules are adsorbed by the polymer at a low surfactant concentration, cs; the adsorption induces a breaking down of the polymer aggregates and the filterability properties of the solutions are greatly improved. An excess of surfactant phase separation is observed by heating at a temperature that is a decreasing function of cs. This is explained by the formation of a complex polymer-surfactant which has the same thermodynamic properties (lower critical solution temperature) as polyethylene oxide and the derived nonionic surfactants.

Structure of Supramolecular Polymers Generated via Self-Assembly through Hydrogen Bonds

The molecular structure and the morphology of self-assembling systems through hydrogen-bonds between complementary molecules has been investigated by electron microscopy and scattering techniques (light and neutron). It is found that in solvents such as toluene one-dimensional filaments are chiefly produced while in solvents such as THF lateral aggregation also occurs.

Light scattering behaviour of semi-dilute solutions of polyacrylamide

Abstract The angular dependence of light scattered by aqueous semi-dilute solutions of unhydrolysed polyacrylamide has been systematically measured as a function of polymer molecular weight, concentration, temperature and time. The behaviour is similar to those already described for other systems of polymer-solvent in the same concentration regime and exhibit a high excess of intensity in the small angle range. These effects are attributed to macromolecule association due to a long range attractive potential; a new expression for the angular dependence of the scattered intensity is developed, taking into account this potential.

Infra-red bandshapes of methylene-d2 bending vibrations in n-hexatriacontane-n-hexatriacontane-d74

Abstract Infra-red spectra in the CD 2 bending vibration region (1080–1100 cm −1 ) have been analysed for mixtures of deuterated and hydrogenated hexatriacontane. The i.r. data analyses are based on lattice dynamical calculations of guest deuterated molecules in the host n-C 36 H 74 and infrared intensities calculated using the electro-optical parameter method. The calculated band profiles as a function of the deuterated molecule concentration compare favourably to experimental spectra taken at 80K. The high resolution, low temperature spectra reveal features heretofore only observed at much higher concentrations of deuterated species. Self deconvolution procedures were used to further resolve the spectra. Excellent agreement was found between calculated and experimental ratios of the i.r. intensity of certain dimer arrangements to that of singlet molecules. This intensity ratio was found to be a better measure of deuterated species concentration than the halfwidth of the CD 2 bending vibration band that had been previously used.