M. Kryszewski

Nanostructured conducting polymer composites — superparamagnetic particles in conducting polymers

Abstract Methods of preparation and the properties of polymer composites with superparamagnetic nanoparticles are reviewed and discussed. Multicomponent polymer systems with nanoparticles of metal oxides can be tailored to exhibit, besides good magnetic properties and transparency, also good adhesion (polymers and copolymers of various types), film forming and processing properties. An interesting feature of polymer composites with nanosized superparamagnetic particles is that, in all cases reported, the measured magnetization considerably deviates from the values calculated or measured for bulk iron oxides (e.g. single crystals). No definite explanation of this discrepancy exists. The studies on a selected system: polyaniline/iron oxide particles help to resolve this question because interactions between the matrix and iron oxide nanoparticles can be studied under different conditions and at different stages of structure formation.

Effect of plasma treatment on surface structure and properties of polyester fabric

Abstract Poly(ethylene terephthalate) fabric was treated by plasma initiated in various gases: nitrogen, oxygen, air, carbon dioxide and ammonia. Plasma-treated fabric showed a considerable change in surface structure and wettability. It was observed that the change in the surface structure of the polyester fibres was closely dependent on the gas type and treatment conditions. The wetting time of plasma treated fabric considerably drops in comparison to untreated fabric and the best results were obtained by treatment in nitrogen, oxygen and air plasma. A good correlation exists between change in the surface structure of the fabric and its wettability. Infra-red a.t.r. spectroscopy showed some differences in the spectra of plasma treated fabrics but these changes are only moderately dependent on the gas type and plasma conditions. Modification of the surface structure of the polyester fibres depends on the current frequency within the studied range of 0.05–100 kHz.

Thermal sampling in polymers with distributed relaxations: PMMA

Abstract The thermal sampling (t.s.) technique, a modification of thermally stimulated discharge (t.s.d.), has been applied to investigate molecular motions in poly(methyl methacrylate) and to compare the results with the theory of t.s. It was found that the distribution of relaxation times is represented by a distribution in activation energies and the temperature dependence of relaxation times is governed by the compensation law. A statistical test confirmed the validity of the compensation effect in the case of glass transition in PMMA. A theory based on self-diffusion has been applied to explain this effect and good agreement of the calculated expansion coefficient with the dilatometric data was obtained.

Structure and electrical properties of polymers with amorphous and crystalline dopants

Complexes de transfert de charge disperses au niveau moleculaire dans les polymeres. Polymeres conducteurs avec un reseau cristallin de complexes de transfert de charge forts

Oligomeric Products in Plasma=Polymerized Organosilicones

Abstract Plasma polymers were deposited from a number of methylsilazane and methylsiloxane monomers of linear and cyclic structure. The oligomeric phase evolved from the polymers by a mild thermal treatment was analyzed using gas chromatography/mass spectrometry combined techniques. The oligomeric phase was found to be composed of the low-molecular-weight products with the weight being mostly no higher than two monomer units. The results suggested that the oligomers might be formed in the gas phase and then they diffuse to the surface of the growing polymer film. The structure of the oligomeric products indicated that their formation must proceed via the Si-N and Si-O bonds fission in silazane and siloxane monomers, respectively. An ionic nature of the primary active species involved in this process was assumed owing to the high susceptibility of these bonds toward heterolytic fission. The postulated ionic mechanism, considered to account for the formation of the observed oligomers, seems to be more reaso...

Gradient polymers and copolymers

Gradient polymers are two component polymeric systems in which the concentration of one component varies in a continuous way from one side to the other in systems with plane-parallel geometry. Such systems can be obtained from an amorphous polymeric matrix by diffusing into another monomer creating a gradient of concentration, which is fixed by, for example, photo-polymerization. Properties of such systems with plane-parallel geometry are discussed. Paricular attention is given to the systems with cylindrical geometry in which the gradient of the second polymer varies from the center to outside. This class of gradient polymers has a great practical application as gradient optical polymeric fibers and multifocal lenses. An interesting and new class of gradient polymers are systems systems consisting of semicrystalline polymeric matrices in which a gradient of structure is created by appropriate thermal treatment and an amorphous polymer gradient is formed by diffusion of a monomer and its subsequent polymerization. The structural, thermal and mechanical properties are discussed mainly for a model system consisting of polyethylene and polystyrene. The polymeric gradient systems, consisting of an oriented semicrystalline polymer and amorphous gradient polymer, are discussed showing that the structurally gradient matrices and amorphous polymer offer a great variety of factors which can influence the properties of multicomponent gradient polymers. Recently obtained gradient copolymers in which the chemical composition varies from one end to the other a macromolecule are presented. It is shown how such macromolecules can be obtained with different type of changes of the composition. The unusual properties of gradient copolymers are discussed considering their mechanical and thermal properties as well their specific behaviour as compatibilizers.

Analysis of relaxation processes in methacrylate polymers by thermally stimulated discharge

Abstract An analysis of relaxation processes in poly(methyl methacrylate), poly(ethyl methacrylate), poly(isobutyl methacrylate) and poly(n-butyl methacrylate) by means of thermally stimulated discharge (t.s.d.), is presented. Distribution functions, calculated from the thermocurrent spectra using the Staverman-Schwarzl transform, are compared with semi-empirical distribution functions of Fuoss-Kirkwood and Havriliak-Negami. Distribution functions of β processes fit the first function very well and those of α processes fit the second distribution function. The distribution parameters are comparable with those in the literature. It is also demonstrated that the activation energy can be calculated from the initial rise by means of the Bucci, Fieschi and Guidi equation, if the proper correction coefficient is introduced, depending on the width of the distribution.

Mechanism of polysilazane thin film formation during glow discharge polymerization of hexamethylcyclotrisilazane

Abstract Preparation of thin polymer films by the glow discharge polymerization of hexamethylcyclotrisilazane has been studied. The effect of basic parameters of the process, such as time, pressure and current density on the polymer deposition kinetics has been established. It has been found that the curves of polymer deposition rate versus monomer vapour pressure have the same shape as the adsorption isotherms. The experimental relationships R = f(p) have been analysed by means of the adsorption equations BET and HJ. A good agreement between the experimental results and adsorption equations suggests an adsorption mechanism of the polysilazane film formation. The effect of polymerization conditions on the properties and morphology of thin polysilazane films has been also investigated.

Thermally stimulated shrinkage forces in oriented polymers: 2. Time dependence

Abstract The four-state model proposed in a previous paper to describe thermal shrinkage in oriented polymers is solved to describe the time dependences of shrinkage forces under constant temperature conditions. The time dependences of shrinkage forces have been recorded for polycarbonate and polyethylene terephthalate at temperatures below the glass transition. It is shown that experimentally recorded time dependences of shrinkage forces can be satisfactorily fitted by dependences predicted by the model, and the comparison leads to reasonable values of activation energy and activation volume for the shrinkage process.

Shrinkage and related relaxation of internal stresses in oriented glassy polymers

Abstract Stability of oriented glassy polycarbonate and poly(ethylene terephthalate) subjected to physical ageing has been investigated in terms of shrinkage forces measurements. It was shown that the temperature and time dependent traces of shrinkage forces are very sensitive to the ageing effects and when compared with the results of other experiments concerning instabilities of oriented polymers they may throw some light on the nature of internal stresses relaxation. Observed shrinkage behaviour was qualitatively described on the basis of a multi-state mechanical model.