T. E. Sukhanova

Morphology, deformation and failure behaviour of homo- and copolyimide fibres ☆: 1. Fibres from 4,4′-oxybis(phthalic anhydride) (DPhO) and p-phenylenediamine (PPh) or/and 2,5-bis(4-aminophenyl)-pyrimidine (2,5PRM)

Abstract The morphology, deformation and failure behaviour of new high-performance polyimide (PI) fibres were examined by scanning electron microscopy (SEM), wide angle X-ray diffraction (WAXD) and tensile measurements. PI fibres were prepared from rigid aromatic diamines p -phenylenediamine (PPh) and 2,5-bis(4-aminophenyl)-pyrimidine (2,5PRM) and semi-rigid 4,4′-oxybis(phthalic anhydride) (DPhO) by wet-spinning of the N , N -dimethylacetamide solutions of their precursor poly(amic acids) in coagulation bath followed by thermal imidization at 400°C. The tensile properties and drawability of copolyimide (coPI) fibres were better than those of homopolyimides (homoPI). The improvement in fibre modulus and tensile strength of the coPI fibres can be explained by the microblock structure on the X-ray level and composed morphology on the macro level. Moreover, changes in the supermolecular structure and apparent fibril sizes, character of morphology, quantity of interfibrillar links, which affect the fracture mode were observed with the different composition of coPI.

Statistical analysis of micro-domain ensembles at the surface of polyamic acid films during their conversion to polyimide

The surface morphology of polyamic acid films evolving to polyimide films is investigated using transmission electron microscopy. Two methods of film conversion, thermal and chemical, are studied. The micro-domains at the surface of the films are shown to form thermodynamically optimised statistical ensemble(s) during polymer conversion. The statistical distribution of the micro-domain diameters is described utilising the model of reversible aggregation. The distribution parameters, aggregation energy and mean diameter of the micro-domains, are shown to depend on the chemical structure of the polymer, the method of conversion and, in the case of thermal conversion, the temperature at which the processing occurs.

Formation of Physical Thermally Reversible Gels in Solutions of Methyl Cellulose in Water and Dimethylacetamide and Properties of Films Thereof

Gelation conditions in solutions of methyl cellulose in water and dimethylacetamide were studied. The gelation mechanisms were studied by X-ray diffraction and photocolorimetry, and their differences in the two systems were revealed. The physicomechanical properties of methyl cellulose films prepared from solutions with preliminary gelation were determined.

Hybrid Polyurethane-Poly(2-hydroxyethyl methacrylate) Semi-IPN–Silica Nanocomposites: Interfacial Interactions and Glass Transition Dynamics

Polyurethane-poly(2-hydroxyethyl methacrylate) semi-IPN-silica nanocomposites with low content (0.25 and 3 wt%) of differently functionalized 3-D fumed silica nanoparticles were studied using a combined AFM/DSC/CRS approach over the −100 to 160°C range. The pronounced heterogeneity of the PHEMA and PU glass transitions’ dynamics and the effects of considerable suppression of dynamics and increasing elastic properties by silica additives were shown. It was caused by formation of peculiarly cross-linked structures due to “double hybridization,” in particular via selective covalent bonding of the silica surface, functionalized by ‒OH, ‒NH2 or ‒CH˭CH2 groups, with the matrix constituents. The silica dispersion remained unchanged in these nanocomposites; therefore the relationships between interfacial interactions and dynamics/modulus behavior could be followed.

Relationship of Processing Conditions to Structure and Properties in PMDA‐ODA Polyimide

A combined wide angle X‐ray diffraction (WAXD)/small‐angle X‐ray scattering (SAXS)/scanning electron microscopy (SEM)/density study of structure and morphology was carried out for a large series of pyromellitic dianhydride‐oxydianiline (PMDA‐ODA) polyimide (PI) samples processed using different powder metallurgy techniques. Using a combined DSC/creep rate spectroscopy (CRS)/long‐term creep resistance (LTCR) approach, their molecular dynamics, thermal and elastic properties, and creep resistance in the temperature range from 20 to 470°C were also studied. Both a choice of the method of formation of fine PI particles and the order of applying high pressure relative to high temperature to form the monolithic samples led to the observation of significant property differences. Relationships between the processing conditions, structure, and properties were determined. As a result, the conditions for optimizing certain PMDA‐ODA polyimide properties, especially creep resistance and elastic properties at extreme t...

Preparation and investigation of polymer-polymer compositions based on polyacrylonitrile and aromatic polyamic acid

A modification of polyacrylonitrile (PAN) was carried out. As a result, a polymer compatible (in contrast to common PAN) with polyamic acid (PAA) was obtained. PAA, PAN and their mixtures in solution and in film were investigated by viscometry, massspectrometric thermal analysis (MTA), TG and electron microscopy. The physico-mechanical characteristics of the corresponding composite films were obtained.ZusammenfassungPolyacrylnitril (PAN) wurde modifiziert, das entstandene Polymer ist (im Gegensatz zu herkömmlichem PAN) ausreichend mischbar mit Polyamicsäure (PAA). PAA, PAN und ihre Gemische wurden in Lösung und als Film mittels Viskosimetrie, massenspektrometrischer Thermoanalyse (MTA), TG und Elektronenmikroskopie untersucht. Die physisch-mechanischen Charakteristika der entsprechenden Verbundstoffilme wurden ermittelt.

Formation of organic-inorganic composite materials based on cellulose Acetobacter xylinum and calcium phosphates for medical applications

The formation of composites based on the cellulose Acetobacter xylinum and calcium phosphates has been investigated using X-ray diffraction, electron diffraction, electron microscopy, energy-dispersive analysis, and differential scanning calorimetry. It has been demonstrated that the planar morphology of calcium phosphate nanoparticles capable of interacting with nanofibrils of the cellulose matrix is an important factor providing interfacial contacts in the formation of organic-inorganic composite materials. It has been established that magnesium-containing calcium phosphates represent two-phase systems consisting of calcium magnesium phosphate Ca2.6Mg0.4(PO4)2 (whitlockite) and hydroxyapatite Ca5(PO4)3(OH). The biocompatibility of the composite materials based on two-phase calcium phosphate systems and the temperature range of their stability (∼20–250°C) determined by the thermal stability of the organic component have been investigated.

Polyrotaxanes composed of β-cyclodextrin and polydimethylsiloxanes: synthesis, morphology and thermal behavior

Epoxy-terminated polydimethylsiloxanes (E-PDMSs) of different molecular weight M n were proved to undergo inclusion complexation into the inner cavity of β-cyclodextrin (β-CD), resulting in polyrotaxanes (PRots). The dethreading of the macrocycle was prevented by blocking the siloxane chain with a bulky substituent derived from 4-aminophenyltriphenyl methane (APhTPhM). As revealed by thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy (SEM), wide-angle X-ray diffraction and statistical analysis of SEM images, the thermal properties and the morphology of polyrotoxanes are dependent upon M n, β-CD/E-PDMS molar ratio and the presence of free β-CD in the complexes.

Nanocomposites Based on Aromatic Polyamide-Imide and Magnesium Hydrosilicate Nanotubes

Structure, morphology, and thermal properties of nanocomposites based on thermally stable poly(diphenyloxydamide-N-phenylphtalimide) (PAI) and layered magnesium hydrosilicate nanotubes (NTs) were studied using thermogravimetric analysis, dynamic mechanical analysis, atomic force microscopy, and differential scanning calorimetry. Thermal stability and glass transition temperature of the composites were shown to exceed those of the PAI matrix. Introduction of NT into the polymer matrix appreciably increased the elasticity and deformability of the composite material. The content of NT was also shown to greatly influence the surface morphology of the PAI-NT composites.

Formation of a composite from Se0 nanoparticles stabilized with polyvinylpyrrolidone and Acetobacter xylinum cellulose gel films

Formation of a composite from Se0 nanoparticles stabilized with polyvinylpyrrolidone and Acetobacter xylinum cellulose gel films was studied. The optimal sorption parameters at which the amorphous form of the selenium complex is preserved in the composite were suggested.