Mario Gleria

Poly(organophosphazene)s and related compounds: Synthesis, properties and applications

Abstract This paper presents an overview of the synthetic procedures used for the preparation of phosphazene compounds. The main reactions used in this field i.e. ring-opening polymerizations, polycondensations and free-radical processes, have been critically reviewed and the possibility of controlling these reactions by using catalysts or inhibitors evaluated. Both low-molecular-weight linear and cyclic phosphazene oligomers and high-molecular-weight phosphazene polymers have been considered.

Aspects of Phosphazene Research

This review reports research carried out by the authors during the last 10 years. The research involves the synthesis, characterization, functionalization, and possible utilization of cyclo- and polyphosphazenes. The investigations concern the synthesis of poly(dichlorophosphazene) by polycondensation reaction of dichlorophinoyliminotrichlorophosphorane; the grafting of unsaturated organic substrates (maleic anhydride, maleates or vinyl polymers) onto poly(organophosphazenes) by free radical reactions and the use of the synthesized materials for the preparation of new grafted copolymers or for the superficial modification of conventional organic macromolecules; the synthesis of phosphazenes containing free hydroxylic groups by reaction of methoxy aryloxy- or methoxy oligoethyleneoxy-substituted cyclo- and polyphosphazenes with boron tribromide or trimethylsilyl iodide and their use for the preparation of new phosphazene-based materials (e.g., sol-gel hybrids, thermosetting resins, azodyes, cyclolinear inorganic–organic polymers sometimes containing chiral units, or organic macromolecules having cyclophosphazene residues as pendant groups); and the preparation of oxazoline-containing cyclic and polymeric phosphazene derivatives for the synthesis of photoinitiators, chain extenders, or blend compatibilizers. The possible developments of this research are also envisaged.

Poly(organophosphazene)s and the sol–gel technique

We report a survey of the utilization of phosphazene materials in combination with metal alkoxide precursors to form ceramics through the sol‐gel technique. Silicon, titanium, zirconium and aluminum three-dimensional oxide networks were exploited for these investigations, while variably functionalized poly[bis (2,2,2-trifluoroethoxy)phosphazene], poly[bis (methoxyethoxyethoxy)phosphazene] and poly [bis(4-hydroxyphenoxy)phosphazene] were used as phosphazene substrates. The resulting new hybrid materials, characterized by SEM, EDAX, DTA, TGA, DSC, DMTA and impedance techniques, showed improved thermal and mechanical stability, and higher ionic conductivity when doped with Li a or Ag a triflates, than those ob

Supported ruthenium nanoparticles on polyorganophosphazenes: preparation, structural and catalytic studies

Abstract Supported Ru nanoparticles on a number of polyorganophosphazenes were prepared and tested for the hydrogenation of unsaturated compounds. The complex Ru(η6-cycloocta-1,3,5-triene)(η4-cycloocta-1,5-diene) was found to be a suitable precursor to deposit metallic nanoparticles on polyorganophosphazenes; upon the removal of cycloolefin ligands under hydrogen atmosphere, highly dispersed metal particles on the polymeric support can be obtained. Ru on polydimethylphosphazene was found to be an active catalyst for the hydrogenation of a wide range of unsaturated substrates (olefins, carbonyl compounds and aromatic compounds) under mild conditions. Polyorganophosphazenes are interesting in their ability to act as either soluble or insoluble catalyst supports, depending upon the dispersing liquid; thus, it is possible to operate in heterogeneous phase as well as in homogeneous phase. The reaction in homogeneous phase can be performed in environmental-friendly solvents such as alcohols and water. The catalyst exhibits high stability towards agglomeration. No significant change in the ruthenium nanoparticles surface as well as catalyst activity was observed.

Organometallic and coordination chemistry on phosphazenes Part I. Zn(II), Pd(II) and Pt(II) complexes on Schiff base-containing cyclophosphazenes

Abstract In this paper we report the synthesis of a new class of cyclophosphazene ligands containing six Schiff bases in the side branches, able to bind transition metals. We describe also the complexation reaction on these substrates of Zn(II), Pd(II) and Pt(II) ions. Elemental analyses together with spectroscopic (IR, UV, 1 H and 31 P NMR) and mass spectrometric (FAB) characterizations reveal that all the above mentioned cyclophosphazenes are able to coordinate six metal ions.

Functionalization of poly(organophosphazenes)—III. Synthesis of phosphazene materials containing carbon-carbon double bonds and epoxide groups

Abstract The chemical modification of hydroxylic group-containing cyclo- and poly-phosphazenes to introduce ethylenic and epoxide functionalities is reported. Thus, hexakis(4-hydroxyphenoxy)cyclophosphazene and poly[bis(4-hydroxyphenoxy)phosphazene] were reacted with carboxylic acids, acyl chlorides and α-bromo-methylene derivatives containing carbon-carbon double bonds, in the presence of bases or suitable condensing agents, to give unsaturated phosphazenes. These substrates were epoxidized successively under mild experimental conditions by reaction with m-chloroperbenzoic acid to produce epoxide-containing phosphazene materials. Possible practical exploitation of these new derivatives is discussed.

New Acid-Polyfunctional Water-Soluble Phosphazenes: Synthesis and Spectroscopic Characterization

Abstract Poly [bis(phenoxy)] phosphazene sulfonic acid and its mixed substitution derivatives containing N-methylsulfonamide, sulfonylaminoacetic, and free sulfonic acid functions have been obtained and characterized by IR and 1H-, 31P-, 13C-NMR spectroscopy. The polymers are all water soluble. Poly [bis(4-benzoylphenoxy)] phosphazene sulfonic acid could not be obtained due to chain degradation during the synthesis.

Photochemistry of tris(2,2′-bipyridine)ruthenium(II) in chlorinated solvents

The photolysis of tris(2,2′-bipyridine)ruthenium(II) in chlorinated solvents at 436 nm and room temperature leads to the formation of cis-dichlorobis-2,2′-bipyridine)ruthenium(II) and 2,2′-bipyridine as the main products.

Photochemical behaviour of poly-(organophosphazenes)—II. Oxygen influence on the photodegradation of aryloxy- and arylamino-substituted polyphosphazenes in solution

Abstract The photodegradations of poly-[bis(β-naphthoxy)] phosphazene and poly-[bis(p-tolylamino)] phosphazene were investigated in methylene chloride solution. A mechanism has been proposed to explain the influence of molecular oxygen on the photoprocesses. Molecular weight variations, results of flash photolysis experiments and the observed post-photochemical effect are in agreement with the suggested mechanism.

Hybrid materials based on the reaction of polyorganophosphazenes and SiO 2 precursors

New molecular composite materials can be prepared based on an inorganic oxide network and an organic polymer. The polymeric component generally requires low process temperatures, due to the presence of the organic backbone or side groups. A sol-gel process therefore is suitable for synthesizing the inorganic component by dissolving soluble polymers into sol-gel precursor solutions in order to obtain ceramic and polymeric solid phases. In this work polyorganophosphazenes were used because they have many technologically interesting properties (chemical, optical, electrical, mechanical). The methods to obtain covalent bonds between polymer and inorganic network and to obtain homogeneous, transparent hybrid materials without phase separation were studied. It was possible to avoid phase separation by preparing phosphazenes containing free hydroxyl functions and by adequately choosing the experimental conditions.