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Conformational parameters of some heterocyclic polymers containing phenyl-substituted quinoxaline units, phthalimide, 3,4,5,6-tetrachlorophthalimide or phenoxy groups, have been calculated by Monte Carlo method. Several physical properties such as solubility, glass transition temperature, initial decomposition temperature and dielectric constant are discussed in relation with the structure of the polymers and rigidity of their chains. The influence of each pendent group on the properties of the polymers was discussed. Keywords: conformational rigidity parameter, heterocyclic polymers, solubility, high thermal stability

This paper deals with the multiobjective optimization problem, applied to the free radical polymerization of styrene. The objectives taken into account and proportionally combined into a scalar objective function are: maximization of the monomer conversion or achievement of a desired value for conversion, minimization of the polydispersity index, minimization of the reaction time, obtaining of a polymer with desired polymerization degree. Using different values of the weights, the objectives which have to be reached and, also, their importance within the polymerization problem are established. The decision variables are the initial concentrations of the two initiators (benzoyl peroxide and tertbutylperbenzoate) and temperature represented by two or three isothermal steps. For solving the optimization problem, several methods are used and compared: sequential quadratic programming, genetic algorithm and a hybrid method obtained by successive use of the two above methods. This last solving alternative improves the results of the optimization procedure. The possibility of changing the weight values of the proposed objectives is a favorable opportunity to consider technological criteria for the optimization problem. Keywords: optimization, free radical polymerization, polydispersity index

The paper deals with the flow analysis of plastic material which flows into the mold cavity using simplifying hypotheses imposed to the injection process. On the basis of software especially developed in C++, the length of the penetration of molten plastic front, volumetric flow rate, time variations of the injection pressure and the radius of the molten front, respectively, have been represented for different plastic materials. Keywords: injection, die forging, fill-in phase, flow front, volumetric flow rate, injection pressure

There were obtained simple thin films of polypyrrole (PPy) and polythiophene (PTh) and double layer films polypyrrole / polythiophene (PPy/PTh) on silicon substrate from deposition in DC plasma reactor. The films obtained were characterized by FT-IR spectroscopy. The influence of thermal treatment on the structure of the films and of interactions at the interface PPy/PTh in 100-400 ºC domain temperatures in argon atmosphere was studied. It was observed that the PPy film processed in plasma is more stable in environmental air that PTh film. It was found that thermal treatment in the range 250-300 ºC in argon atmosphere release interaction between PPy/PTh films. The principal phenomenon observed in the double layer was one of protection of the more reactive PTh film counter oxidation process by coating with PPy layer. Keywords: plasma polymerization, thin films, interfaces phenomena

Photochromic compounds are able to change their absorption spectra when exposed to light or dark condition. This process is reversible when the photochromic moieties exist, as usually occurs, in two different forms, whose relative concentration depends on the wavelength of incident light. Polymers with side-chain photochromic groups have recently attracted a great deal of interest because the photoisomerisation of the chromophores can induce reversible variation of the macromolecular structure and hence their physical properties. Keywords: photochromic, polymeric materials

Low density polyethylene films were g-irradiated in various oxidative environments: air and aqueous solutions containing hydrochloric acid and different chlorides (MnCl2, CuCl2, NiCl2, and CoCl2) in the concentration of 10 % (w/w). Radiochemical degradation of polyethylene was assessed by IR spectroscopy at various characteristic vibration regions: 1720 cm-1 (C=O band), 3440 cm-1 (OOH/OH band) and 1630 cm-1 (C=O in the vicinity to C=C). Low dose rate (0.4 kGy/h) was applied over the dose range 0-4.5 MGy at ambient temperature. The two main processes occurred during high energy exposure: degradation and crosslinking were pointed out. Keywords: polyethylene, degradation, aqueous solutions, IR spectroscopy

Two new bismaleimides with preforming ester and amide linkages in the main chain were prepared by the reaction between the chloride of 4-maleimidobenzoic acid and 4 (5) amino- salicylic acid. The structures were characterized by elemental analysis, infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy and thermogravimetric analysis. Keywords: bismaleimides, polyimides, thermal stability

The oxidability of low density polyethylene stabilized with several antioxidants was investigated by oxygen uptake. The radiosterilization doses (5, 10 and 20 kGy) were applied for characterization of antioxidant activity of calix[4]arene, Santonox R, Ionox 220, Irganox 1076, Irganox 1081, tri-t-butylphenol and elementary selenium. Their contribution to the radiostability of LDPE is discussed in comparison with control sample. The order of increasing the oxidation induction time was established for depicting the evolution of oxidative degradation in stabilized polyethylene. Keywords: low density polyethylene, stabilization, radiosterilization

Controlled/living radical polymerization (CLRP) is a field that has been expanding continuously during the last 15 years, as the method allows for the synthesis of well-defined polymers under mild conditions. Many CLRP systems have been developed, all of them relying on an equilibrium between a minute concentration of radicals and a large amount of dormant species. Among them, atom transfer radical polymerization (ATRP) has evolved as one of the most versatile techniques for the production of well-defined materials. This paper briefly reviews the fundamentals of ATRP, while a future paper will be discussing the applications. Keywords: controlled/living radical polymerization, atom transfer radical polymerization, transition metal catalysis

By replacing polystyrene hard blocks with poly-á-methylstyrene ones, the service temperature of thermoplastic elastomers can be considerably enhanced, because the glass transition temperature of the latter is about 170°C. The thermodynamics of polymerization of á-methylstyrene is well-known (ÄH and ÄS are -35.1 kJ.mol-1 and -104 J.mol-1 K-1, respectively) so that the “ceiling” (equilibrium) concentration of AMS at various temperatures may be calculated. The living polymer molecules can attain a state of dynamic chemical equilibrium with the monomer molecules. If the temperature is subsequently raised above the ceiling temperature, the Gibbs free energy again favors the monomer. The higher the á-methylstyrene concentration and the lower the polymerization temperature, the higher is the achievable monomer conversion, but never hundred percent. Using n-butyllithium initiator alone, at low reaction temperature, when the maximum achievable theoretical conversion is the highest, the polymerization of á-methylstyrene occurs very slowly in hydrocarbon reaction media. Sasol Germany GmbH developed a high performance living anionic polymerization active center modifier, the purity of which is in agreement with those imposed by the highly sever conditions imposed by these reactions: 2-(2-ethoxyethoxy)-2-methylpropane. The purpose of this paper is to establish a regression model in order to determine the optimal conditions (temperature, reaction time, active center modifier concentration) of á-methylstyrene anionic polymerization in toluene (melting point – 93°C), initiated by n-butyllithium – 2-(2-ethoxyethoxy)-2-methylpropane system, using the factorial design of experiments. Keywords: polystyrene, poly-á-methylstyrene, n-butyllithium