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The amphiphilic polymers can form associated structures in aqueous solution by mutual interaction and/or interaction with other components such as surfactants and active colloidal molecules. In this paper, results regarding nanolevel associative behaviour of chitosan based systems with surfactant and paracetamol are presented. The viscosity measurements of the solutions prepared were made with a view to take into consideration viscosity as an associative parameter. The thin films topography obtained by spin-coating was analyzed by Atomic Force Microscopy (AFM). The nanostructured matrices were investigated by Scanning Electronic Microscopy (SEM), X-Ray Diffraction (XRD) and by Fourier Transform InfraRed (FTIR) Spectroscopy. From FTIR and X-Ray investigations it can be concluded that, at nano - level, in the chitosan matrix, crystalline surfactant and paracetamol domains like nanocapsules are localized. By visual analysis of the AFM and SEM images it can be observed that the nanocapsules are orderly structured in horizontal layers and present a vertical gradient, the paracetamol nanocapsules formed having dimensions in the range of 21 – 170 nm. The chitosan-paracetamol nanostructured matrices obtained by the phase inversion method stand as a remarkable candidate to be used to control release of this drug. Keywords: chitosan, paracetamol, cationic surfactant, structural analysis

The paper presents the corotating twin screw extruder optimization, taking into account the quality of final product. Thus it was established the optimum screws configuration, the optimum screw speeds and the optimum flow rates. Keywords: twin screw extruder, quality, flow rate, screw

A new aromatic diamine, namely 2,2-bis(3-amino-4-oxyhexyloxy-phenyl-4’-butoxyazobenzen) hexafluoropropane, containing two azobenzene side groups have been prepared by modification of 2,2-bis(3-amino-4-hydroxyphenyl) –hexafluoropropane with 4-(6-bromohexyloxy)-4’-butoxyazobenzene in the presence of K2CO3/KI. This monomer showed a mesophase in the range of 103-114°C and can be used for obtaining of polymers with special optical properties. Keywords: butoxyaniline, side azobenzene groups, thermal characterization

Knowing that copolymers of acrylonitrile (AN) with acrylic acid (AA) can be used for the molecular imprinting, three AN: AA copolymers were synthesized by radical copolymerization in emulsion without emulsifier. The copolymer and diosgenin were dissolved in dimethylformamide (DMF) in order to obtain casting solutions with various polymer and template concentrations. The influence of the copolymer and template on the rheological behavior of the solutions was studied in order to establish the best parameters for the casting solutions preparation. The polymer solutions were transformed in membranes by phase inversion in water at room temperature (20oC). By casting the polymer solutions on a glass surface and drawing down with a scraper, a 200 mm thickness film resulted. The diosgenin was extracted from the membrane structure with ethanol, methanol or chloroform in an ultrasonic bath. The molecular imprinting was proved by HPLC on liquid (the extracting solvent after the membrane extraction) and solid phases (after dissolution of membrane parts in DMF). Comparing the sorption capacities of the imprinted materials, for two steroids (diosgenin and stigmasterol), the membrane selectivity towards the template was proved. Keywords: imprinted polymer, molecular recognition, solid phase extraction, bioactive substances,phase inversion

The paper presents a comparative study on the structure of some polyvinyl alcohols used in PVC-S technology. The obtained data clearly showed that the degree of hydrolysis can be determined, with the same high precision through chemical method, IR and 13C-NMR spectra. The carbonyl content determined from the IR spectra also correlates with the carbonyl content determined from 13C-NMR spectra. A fast and reliable IR method for checking the degree of hydrolysis as technological support can be provided, the normalized carbonyl content determined from IR spectrum being linearly correlated with the degree of hydrolysis. Keywords: Polyvinyl alcohols, vinyl alcohol-vinyl acetate copolymers, IR spectra, 1H-NMR spectra, 13C-NMR spectra

Hydrogels are networks consisting of crosslinked hydrophilic polymers that absorb and retain water or biological fluids. Poly(vinyl alcohol) (PVA) based hydrogels are non-toxic, non-carcinogenic, easily processed and therefore have been examined for tissue replacements, artificial skin, hemodialysis membrane and oral drug release systems. The research focuses on the synthesis of PVA–acrylamide based hydrogels, using glutaraldehyde, sodium tetraborate and N,N’-methylenebisacrylamide/sodium tetraborate mixture as crosslinking agents. The crosslinking copolymers were characterized by infrared spectroscopy (IR), thermal analysis (TG, DSC), and swelling behaviour in distilled water at 37.5 0C temperature. Keywords: crosslinked copolymers, poly(vinyl alcohol)-acrylamide, glutaraldehyde, sodium tetraborate, N,N’-methylenebisacrylamide

The new materials have physical and mechanical properties that allow their processing by using classical methods, specific for synthetic polymers. In vitro biocompatibility studies were performed on a primary culture of human dermal fibroblasts by the MTT test. The biocompatibility of the materials was tested in vitro by determining cell viability in a culture of human dermal fibroblasts by using the MTT method. The physical and mechanical properties and also the biocompatibility properties of the new materials recommend them to be used in the manufacture of medical devices. Key words: synthetic polymers, natural polymers, blends, polyvinyl chloride, collagen, elastin, biocompatibility, cell viability

Complete dentures technology uses especial heat curing acryllic resins, which are included in DIN EN ISO classification at number 1567, group 1. Polimetacrilates are fragile materials, which fracture easily and often need prosthetic pieces repairs. Evaluation of acryllic resins structural qualities allows choosing of the material with maximum mechanical resistance. Present paper intends to determine some comparative structural studies of three heat curing acryllic resins, concerning behaviour after mechanical testing . There were realized 8 samples from each heat curing resins (Meliodent, Superacryl, and Vertex), using the complete denture technology recommended by the producer. Their mechanical characteristics were determined with help of Zwick Roel equipment. Transversal and longitudinal sections of the fractured zones were evaluated by stereomicroscopy and scanning electron microscopy. Following the mechanical tests, there were obtained the following results: ultimate tensile strength 64 MPa / Meliodent, 66 MPa/ Superacryl, Vertex/ 70MPa; total elongation was 11% for Meliodent, 9% for Superacryl and 5% for Vertex; Young’s elasticity modulus was 4570MPa for Meliodent, 5125 MPa for Supercryl and 6243 MPa for Vertex. By stereomicroscopy there was noticed fragmentation, number of fibres from the transversal cross section, or the aspect, shape, colour of fibre from the matrix. At the scanning electron microscopy, microscopic features may be put in evidence: the aspect of the broken matrix (which is brittle for all the samples), the manner of fracture, the nature of the interface, which is incoherent. Finally the correlation between mechanical behaviour and fracture mechanism was made for dental heat curing resins. Keywords: heat curing acryllic resins, stereomicroscopy, scanning electron microscope

This paper presents the influence of the processing temperatures on the physical–mechanical properties of polyoxymethylenes (POM) used in injection molding of high performance sport products. The test-pieces were obtained by processing POM at the following temperatures: 180°C, 190°C, 200°C, 210°C, 220°C, 230°C and 240°C. It was established that the pressure in the mold decreases as the processing temperature increases. Further, thermal analyses (TG, DSC and DMA) were performed and it was noticed that the processing temperature had an influence on the thermal stability of the polymer, but the vitrification temperatures (Tv) and the melt temperatures (Tt) were poorly influenced by the processing temperature. Keywords: polyoxymethylene (POM), injection molding, Thermogravimetry (TG), Differential Scanning Calorimetry (DSC), Dynamic-Mechanical Analysis (DMA)

This paper presents the synthesis and study of some Mn(II) coordination polymers hybrid with the following acids as ligands: dibuthilphosphinic, dibuthiltiophosphinic, dibutildithiophosphinic, dioctilphosphinic, dioctiltiophosphinic, dioctilditiophosphinic. The study was performed by means of chemical analysis, gel chromatography, IR spectroscopy, ESR, X-ray diffraction, thermogravimetry. The experimental results were used to propose the structural formulae of these compounds and to calculate the kinetic parameters of the thermal decomposition reactions.