Drahomíra Hlavatá

The effect of polymerization temperature on molecular weight, crystallinity, and electrical conductivity of polyaniline

Abstract The influence of the polymerization temperature (from −50 to +50°C) on molecular weight, crystallinity, and electrical conductivity of polyaniline has been investigated. Aniline was oxidized in aqueous medium with ammonium peroxodisulfate at equimolar and excess concentrations of hydrochloric acid. The reaction mixture freezes below −10°C and the polymerization of aniline then proceeds in the solid state. As the reaction temperature decreases, both the molecular weight of polyaniline (determined by gel permeation chromatography) and its crystallinity (observed by X-ray diffraction) increase. The morphology of polyaniline changes from granular (reaction in a liquid medium) to macroporous (polymerization in the frozen state). Electrical conductivity of polyaniline is higher for samples prepared under more acidic conditions. It was found to be independent of the polymerization temperature and, consequently, of the molecular weight.

Compatibilization of high-impact polystyrene/polypropylene blends

Abstract Effects of three different linear styrene—butadiene block copolymers on morphology and selected mechanical properties of high-impact polystyrene/polypropylene blends were investigated. Scanning and transmission electron microscopy and small-angle X-ray scattering were used for the determination of the blend morphology. Impact strength, elongation at break and flexural modulus were measured for further evaluation of the compatibilizer efficiency. A similar effect on the particle dispersion was found for all three copolymers but both the styrene-terminated multiblocks influence formation of interfacial layer and consequently the related mechanical properties in a much more pronounced way than the diblock. Small-angle X-ray scattering was found to be the appropriate technique for the determination of triblock concentration necessary for covering a given interfacial area (critical concentration).

Conductivity ageing in temperature-cycled polyaniline

The conductivity of polyaniline (PANI) hydrochloride was measured in situ during successive temperature cycles from room temperature to 85, 115, 146 and 179 °C. FTIR spectroscopy, gel-permeation chromatography and X-ray diffraction assessed the changes in polymer structure after each run. The conductivity ageing of PANI in terms of deprotonation, degradation and crystallinity reduction is discussed. The behaviour of PANI in compressed pellets and as powders is compared.

Waxs and saxs investigation of polypropylene crystalline phase in blends with high-impact polystyrene and compatibilizers

Abstract On the basis of combination of wide-angle and small-angle X-ray scattering, the character of the polypropylene crystalline phase and its content were studied in polypropylene-high impact polystyrene blends, compatibilized by styrene-butadiene block copolymers. Addition of a copolymer slightly reduces the crystallinity of polypropylene. In the absence of the compatibilizer no miscibility of the components was observed. In all samples polypropylene maintains its α-crystalline phase.

Preparation and characterisation of hybrid organic/inorganic coatings and films

SummariesHybrid organic/inorganic coatings and free-standing films made from GTMS [3-glycidyloxy)propyl]trimethoxysilane, GMDES [3-(glycidyloxy)propyl]methyldiethoxysilane, poly(oxypropylene) of different molecular weights end-capped by amino groups (Jeffamine D-230, D-400 and T-403), and in some cases, colloidal silica, were prepared and characterised. Hydrochloric acid as a catalyst for the sol-gel process and water/propan-2-ol mixture as a solvent were chosen. The structure, morphology and mechanical properties of these scratch-resistant systems were studied by static and dynamic mechanical analysis, small-angle x-ray scattering, NMR spectroscopy and atomic force microscopy. The coatings were fully transparent and colourless with a smooth surface and showed suitable mechanical properties.RésuméDes films indépendants [freestanding] et des revêtements hybrides organiques/inorganiques, préparés à partir du GTMS [3-(glycidyloxy)propyl]triméthoxysilane, GMDES [3-(glycidyloxy)propyl] méthyldiéthoxysilane, poly(oxypropylène) de poids moléculaires variés et dont les extrémités se terminent par des groupes amino (Jeffamine D-230, D-400 et T-403) et dans quelques cas par la silice colloïdal, ont été préparés et caractérisés. On a choisi l’acide chlorhydrique en tant que catalyseur pour le procédé sol-gel et une mélange eau/propan-2-ol comme solvant La structure, la morphologie, et les propriétés mécaniques de ces systèmes qui résistent aux eraflures ont été étudiées par le moyen d’analyses mécaniques statiques et dynamiques, de la diffusion x aux petits angles, de la spectroscopie NMR et de la microscopie force atomique. Les revêtements étaient tout à fait transparents et incolores, ayant la surface lisse. Ils ont manifesté des propriétés mécaniques pertinentes.ZusammenfassungHybrid organische/anorganische Beschichtungen und freistehende Films aus GTMS [3-(Glycidyloxy)propyl]trimethoxysilan, GMDES [3-(Glycidyloxy)propyl]methyldiethoxysilan, Poly(oxypropylen) von verschiedenem Molekulargewicht, die mit Aminogruppen wie Jeffamine D-230. D-400 and T-403 endverkappt sind, und in einigen Fällen aus kolloiden Silikaten, wurden hergestellt und characterisiert. Wir verwendeted Salzsäure als Katalyst für den Sol-Gel Prozess und eine Mischung aus Wasser und Propan-2-ol als Lösungsmittel. Wir studierten die Struktur. Morphologie und mechanischen Eigenschaften dieser kratzfesten Systeme durch statische und dynamische mechanische Analyse, Kleinwinkel-Röntgenverteilung, NMR Spektroskopie und Atomkraftmikroskopie. Die Beschichtungen waren völlig transparent und farblos mit einer glatten Oberfläche, und zeigten geeignete mechanische Eigenschaften.

Heat-induced transition of polystyrene- block-poly(ethylene-co-propylene) micelles in decane and in dioxane

Abstract Dissolution of polystyrene-block-poly(ethylene-co-propylene) (PS—PEP) in decane, a selective solvent for the PEP block, and dioxane, a selective solvent for the PS block, at room temperature leads to formation of metastable micellar structures, which convert into stable micelles with molar mass reduced several times after heating above ∼50°C. By comparing small-angle X-ray scattering (SAXS) and light scattering (LS) data, the following models of micellar structures are suggested: At room temperature, dissolution of PS— PEP in decane yields aggregates of micelles. These are detected by LS, while SAXS reflects the molar mass of individual micellar cores formed by PS blocks. At elevated temperature, these compound particles disaggregate and then reorganize into equilibrium micelles of reduced molar mass. Solutions of PS—PEP in dioxane at room temperature have a different character. The molar masses of the observed particles determined by SAXS are in a good agreement with LS results, so we can exclude aggregation of micelles in this solvent. Nevertheless, also here, after heat treatment, both SAXS and LS yield a molar mass that is about 5 times lower than that determined for unheated solutions. Metastable structures surviving from the solid-state morphology after dissolution in a selective solvent at room temperature may convert to classical equilibrium micelles only after heating.

FTIR study of polyaniline–fullerene complex

Polyaniline-fullerene composites prepared either by solid-state blending of both components (composite I) or by the introduction of fullerene during polymerization of aniline (composite II) have been studied by FTIR spectroscopy. An interaction between fullerene and imine groups of polyaniline base was observed. The size of fullerene crystallites decreased after the mechanical blending of components in composite I. The formation of polyaniline-fullerene complex comprising the structure corresponding to a doped polyaniline was proved by wide-angle X-ray scattering analysis in composite II.

SAXS, SANS and photoelasticity of poly(N,N-diethylacrylamide) networks: 1. Structure changes after temperature jumps

Abstract The development of microphase separation after temperature jumps in poly(N,N-diethylacrylamide) hydrogels was studied by means of small-angle neutron (SANS) and X-ray (SAXS) scattering. The curves of excess SANS and SAXS for temperature jumps from 25 to 30°C were different in character from those for jumps from 30 to 35°C. After the temperature jump from 25 to 30°C two polymer phases with different water content are formed (excess scattering intensity Iex ∼ q−2, where q is the length of the scattering vector); however, after the jump from 30 to 35°C the dilute phase is formed by water droplets (pronounced two-phase structure, Iex ∼ q−4). Photoelastic measurements on the equilibrium swollen samples indicate that correlations exist between side groups at temperatures greater than or equal to 33°C. The association of side groups leads to microsyneresis and to the differences observed in scattering behaviour.

Organic Nanocolloidal Polyaniline Dispersions Containing Fullerene

Abstract Polyaniline‐fullerene (C60) composites with nanoscale level ordered structure were prepared by the interfacial polymerization of aniline hydrochloride in water‐benzene emulsion containing fullerene. UV‐visible spectra, FTIR spectra and wide‐angle X‐ray diffraction were used to characterize the resulting materials. The luminescence measurements suggest the formation of a complex between conducting polymer and fullerene.

Stability of electrical properties of conducting polymer composites

The effect of slow cycle heating and cooling on the stability of electrical properties of two polymer composites- polypropylene/polypyrrole (PP/PPy) and polypropylene/carbon black (PP/CB) - was investigated. Conductivity in composites was measured in heating/cooling cycles in the temperature range from 16 °C to 105 °C in PP/PPy and to 125 °C in PP/CB, respectively. It was found that the thermal treatment caused the decrease of PP/PPy conductivity while in case of PP/CB the treatment increased the electrical conductivity. The positive effect was explained by increased crystallinity in the thermally treated composite.