I. Katime

Observation d'une transition conformationnelle dans le PMMA

Abstract Intrinsic viscosity and light scattering measurements on fractionated samples of atactic poly (methyl methacrylate) show a conformational transition around 45–50° in toluene and benzene but not in 2-heptanone. The transition is detected by a stepwise change in K θ (i.e. the unperturbed dimensions) with increasing temperature.

Investigation of conformational transition in poly(methylmethacrylate)—III Aromatic esters as solvents

Abstract Light scattering and viscosity measurements on fractionated samples of atactic PMMA in methyl and ethyl benzoates show the existence of a conformational transition in the temperature ranges 45–50° and 40–45° respectively. The study of unperturbed dimensions and polymer-solvent interaction parameter shows that the phenomenon affect both inter- and intramolecular interaction. This effect modifies the flexibility of the macromolecular chain and other properties in solution, e.g. intrinsic viscosity.

Investigation on conformational transition in PMMA—II: Aliphatic esters as solvents

Abstract It has been found that PMMA changes its conformation in ethyl and butyl acetates over the temperature range 40–50°. At the same time it has been observed that solvent plays an important role in the phenomenon. This conformational change affects all polymer solution properties, such as intrinsic viscosity, mean radius of gyration, chain flexibility, etc.

Conformational transition in syndiotactic PMMA: 6. Mono- and dichlorobenzene

Abstract We have studied the thermal behaviour of syndiotactic PMMA in several solvents by viscometry. We have found a conformational change in the temperature range 293–308 K.

Polymerization of vinyl acetate in microemulsions stabilized with dodecyltrimethylammonium bromide and cetyltrimethylammonium bromide

The polymerization of vinyl acetate in microemulsions stabilized with dodecyltrimethylammonium bromide (DTAB), cetyltrimethylammonium bromide (CTAB) or mixture of these surfactants is examined. The polymerization rate diminishes as the surfactant mixture becomes richer in DTAB. Also, particles grow with conversion and become increasingly larger as the DTAB content in the mixture increases. Our results indicate that chain transfer reactions to monomer are more important than chain transfer reactions to polymer even at high conversions with CTAB. However, as the content of DTAB increases, bimolecular termination induced by coagulation, terminal double bond polymerization and chain transfer reactions to polymer become increasingly more important.

Polymer cosolvent systems. 8. PMMA/CCl4/(ISO)amyl acetate. Study by laser light scattering and viscometry

Abstract Two new non-symmetrical cosolvent mixtures for PMMA are reported in this work. Unperturbed dimensions, Mark-Houwink-Sakurada constants, second virial coefficients and preferential sorption coefficients have been determined for both systems at 298K using as experimental techniques viscometry and laser light scattering. The results indicate that both mixtures (CCl 4 /(iso)amyl acetate) are poor cosolvents for atactic PMMA, the mixture formed by amyl acetate being a better cosolvent than the mixture formed by isoamyl acetate. In both systems no inversion in solvation was found: the acetate is preferentially adsorbed on PMMA over the whole composition range. In order to predict the experimental preferential sorption coefficients the Read equation has been used, obtaining the polymer liquid interaction parameters X ij . by means of the Blanks-Prausnitz criterion.

Novel functionalized nanohydrogels, synthesis and some applications

A functionalized nanohydrogels have been synthesized by two step procedure. The first step implies an inverse microemulsion polymerization of p-nitro phenol acrylate (NPA) and N-isopropylacrylamide (NIPA) using Aerosol (AOT) as a surfactant and ethylene glycol dimethacrylate (EGDMA) as a crosslinking agent. The polymerization reaction was performed in presence of an oil-soluble salt to reduce the dimensions of the micellar diameter. The second step includes a chemical functionalization by nucleophilic substitution reaction over the carbonyl groups. The average particle diameter and the particle size distribution of the nanohydrogels were measured in acetone at 25?C by quasielastic light scattering (QLS) showing average diameter of 22 nm. The nanogels were characterized by FTIR-ATR, 1HNMR, UV-vis spectroscopy and DSC.

Low frequency dielectric relaxation study in PMMA/PS blends

Abstract The dielectric behaviour of solution-grown films of poly (methyl methacrylate) (PMMA)-polystyrene (PS) blends has been studied as a function of frequency and temperature. The obtained results show that the β process observed in the PMMA/PS system is associated with the PMMA fraction in the blend. From the dielectric results we found that the local conformational states of the PMMA chain are perturbed by blending with a PS content higher than 9–13%, as a result of the incompatibility of this system.

Poly(N,N-dimethylacrylamide)/copolymers of vinyl alcohol blends: effect of the comonomer

Abstract The miscibility behaviour of poly( N , N -dimethylacrylamide) (PDMA), with poly(ethylene-co-vinyl alcohol) (EVAL) of different compositions has been investigated and compared to that of the blends with poly(vinyl acetate-co-vinyl alcohol) (ACAL). Differential Scanning Calorimetry (DSC) results indicate that PDMA is miscible with EVAL78, EVAL68 and EVAL56 but immiscible with EVAL25, which has lower degree of hydrolysis. The limit of miscibility is lower in this case, indicating the influence of the vinyl alcohol content in miscibility. Fourier transformed infrared spectroscopy (FTIR) studies of miscible blends reveal the existence of specific interactions by hydrogen bonding between hydroxyl groups in vinyl alcohol units of the copolymers and the amide-carbonyl group in the PDMA, which appear to be decisive for miscibility.

Polymer Cosolvent Systems 3. PMMA(3)/CCl4 (1)/n-Butyl Chloride(2)

SummaryIn this paper we have studied the behaviour of PMMA in the binary mixture CCl4/n-butyl chloride by viscometry, light scattering and dyalisis. We have found that the CCl4/n-butyl chloride mixture behaves as cosolvent in the range 10 < u2 < 90% n-butyl chloride. The n-butyl chloride is preferentially adsorbed in the whole composition range. The obtained results are discussed attending to GE and the liquid order.